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Before your gemstone can become the centerpiece of a beautiful piece of jewelry, ensure you finish the job by polishing it well. Many polish gems with a rock tumbler, though some jewelers/stone cutters do so with a polishing compound, by hand, or other methods. POLISHING WITH A ROCK TUMBLER As you prepare your gems to become beautiful pieces of jewelry, shining them is among the most important steps. With this in mind, rock tumbling is one of the many different methods for polishing gemstones. Begin this process by placing your stones in the tumbler barrel with water and grit. The grit works similar to sandpaper on wood, smoothing out your material with friction. The stone will go through several phases of shining/sanding; you’ll begin with coarse grit and end with a polishing agent. However, before choosing this method of polishing, consider: The type of jewelry and gemstone The hardnesses of the materials Some gemstones are too soft for rock tumbling, while others are too hard. Moreover, a low-quality gem could break if it is put in the harsh conditions of a tumbler. It is important to understand the materials you are working with to ensure you get the best end-result possible. Expert Jewelers recommend using high-quality tumblers for polishing jewelry or other metals, as these machines can withstand more weight and are more durable. Jewelry with be more harsh on your tumblers and will require a different form of media in order to get a good shine. The best combination for polishing metal is red rouge polish with walnut shell as the filler. This combination will polish copper, silver, gold, and other metals! POLISHING WITH A CABBING MACHINE One of the most common ways to polish a gemstone is with a cabbing machine. Cabbing Machines are used to cut, sand, and polish gemstones. They are extremely efficient and will result in the fastest finish. If you are seriously interested in learning how to cut and polish gemstones, then Cutting Edge Supply highly suggests that you try one out! Usually cabbing machines will come with everything you need in order to get started polishing. Find a wide variety of different styles on our website. We also have a couple amazing articles on our website that explain how to choose a cabbing machine and go over the fundamentals. POLISHING WITH A DREMEL A Dremel tool can also polish stones and metals if you equip it with the right bit. Begin by using a sandpaper bit to smooth out your material. After sanding your stone down, you’ll then utilize a polishing buffing wheel to buff out the stone and bring out its luster. The tools you will need to do this are: Flex Shaft or Dremel Bristle Brushes (Possibly hard felt wheels) Diamond Compound You will use these three products to polish the surface of your gemstone after you have sanded it. These are the most basic tools and as you start you might find that Diamond Smoothing discs, nova points, or other bits might work better or make things easier. Many use this method to polish their stones or metal because you can equip the Dremel with different accessories to complete the job. It also allows you to reach areas you would not be able to reach with a cabbing machine or tumbler. POLISHING GEMSTONES WITHOUT TOOLS Lastly, if you don’t have a rock tumbler, cabbing machine, or Dremel tool, you can polish rocks without machines by using a diamond powder and denim. Begin by applying some of the compounds to your fabric, then rubbing the gem’s surface. Pressure and surface tension will start to create heat and it will speed up the polishing. However do not get your stone too hot because it can break. If you have sandpaper nearby, try sanding the surface of the gemstone with a #120 grit and going up to a #600 or #1200 grit. Once you have completed that, use the denim like we mentioned before. This will give you a fabulous looking gemstone. There are many different methods for polishing gemstones, so do what works best for you with the tools you possess. Before you begin polishing your stone, make sure you understand the material you’re working with, as all stones have different levels of hardness. (Denim will work best on soft stones. Hard stones will need a cabbing machine, Dremel, or rock rock tumbler. What works best for one is not ideal for all. Taking the stone into account ensures you use the right polishing compound to put the finishing touches on your gem. Purchase the best tools and polishing compounds at Cutting Edge Supply to ensure the stones you work with never lack luster.

HOW TO CHOOSE A GRINDING WHEEL M any of us have used grinding wheels as part of our regular, daily work functions, but most of us don’t know why we use the wheel we do, or even if the wheel we are using the right one for the job. There are many different types of abrasive grains, available in a whole range of grit sizes and held together by different bonding agents. How do we know which to use? It's simpler than we might think. A grinding operation is a system, and as a whole, there are many parts to consider. One key component is the wheel. To determine where to start, consider the seven operational factors. The Material Being Ground The Severity of the Operation Required Finish and Form Accuracy Area of Contact Wheel Speed Coolant Use Machine/Spindle Horse Power By taking each of these seven factors into consideration, it is possible to narrow the field down to a smaller list of options to start with for any grinding operation. 1. THE MATERIAL BEING GROUND The first thing to consider when selecting a grinding wheel specification is what are we grinding? What is the material, and how hard is it? Is it easy to grind or difficult? By reviewing these elements, we can select the correct abrasive type, the grain’s attributes, the appropriate grit size, and bond type. Knowing the properties of the material we are working with helps us select the proper abrasive grain and its attributes. By convention, we use aluminum oxide grains for grinding ferrous metals and silicon carbide for non-metals and non-ferrous metals. Ceramic and superabrasive grains can be used on either but generally under specific circumstances where the material being ground requires these types of grains or when we are looking to optimize process performance. Once we know which grain type to start with, we can look at the material grindability. If the material is easy to grind, we will want to use a tough/durable grain. Since the material is easy to grind, the grain shouldn’t break down too soon or too easily, so the whole grain can be used to maximize wheel life. For materials that are hard to grind, we will want to use a mild/friable grain, which fractures more easily, stays sharper, and actually grinds the material. For easy to grind materials, we would want a coarser grit. This is because the grain can easily penetrate the material, make and remove chips. Using a larger or coarser grit maximizes the stock removal, reducing cycle time. Another aspect of the wheel we can dial in on based on the material being ground is the grade or hardness of the bond. If the material is considered easy to grind, we can use a harder grade, which ensures that the wheel doesn’t release the grain before it is consumed. Knowing that we want to use the abrasive grain for as long as we can, we want the bond to hold that grain in the wheel for as long as possible. If the material is difficult or hard to grind and we use a blocky, tough, and durable grain, we run the risk of simply dulling the grain and opening the door to finish issues, such as burning, because the grain will rub and not grind. The material being ground also helps us determine the grit size. For hard to grind materials, we would recommend a finer grit size because a smaller particle will penetrate hard materials and form a chip easier than a larger blockier one. Difficult or hard to grind materials are abusive to the abrasive grain and can cause them to blunt or dull. Since we need more sharp points to penetrate the material, we want to ensure the grains are being released before they become too dull and cause metallurgical damage. With hard materials, a softer grade should be used so that the material is constantly being exposed to sharp grains. The grade needs to be soft enough to release the dulled grains and keep exposing new sharper grains to the work. 2. THE SEVERITY OF THE OPERATION Here we consider how much or how heavy the grinding pressure will be in the grind zone. The higher the grinding pressure or force per grain, the more severe the operation. It is operations like these where today’s ceramic and superabrasive grains do well. Much like the material we are grinding, severity of operation helps us determine the attributes of the abrasive grain. For operations with heavy pressure or high force per grain, we will use a tough/durable grain because this type of grain can tolerate the large amount of pressure generated during the operation. Tough/durable abrasives are better able to withstand the pressure and not break down too soon, allowing them to perform the required work. Severity of operation also helps determine the grit size. For operations that are more severe or have heavy pressure, we want to use a coarser grit so that the grain will hold up to the grinding pressure. There may be times where we want to distribute the force/pressure over more cutting points, but even in that situation, we need the grain to be as coarse as possible to tolerate the pressure without turning to dust. The last part of the wheel spec that severity of operation helps us determine is the grade of the bond or hardness of the wheel. Where we have heavier pressure, we naturally go with a harder grade for the wheel because we want the wheel to hold up under the forces of the grind operation - to hold on to the grain long enough for it to do the work we need it to do. In short, a harder bond is required so that it will hold the grains long enough to be used fully and not released too soon. For operations with light pressure or lower force per grain, we use a mild/friable grain. When the severity of operation is low, we don’t want a durable grain that will only rub and dull. We need one that will continue to break down to expose new sharp cutting points, and mild or friable abrasives do this better, keeping sharp grains in contact with the material. For light pressure operations, we use finer grit sizes. Since the pressure per grain will be lower overall, we need to make sure the grain is still able to fracture properly; if it's too coarse, the grain may not break down and self-sharpen at all. When working under light pressure, a softer grade can be used because we need the wheel to break down and release the dull grain before it starts to rub and heat or burn. We also want the wheel to break down to bring new sharp grains to the cutting surface so we can perform the required work and get the desired performance from the grain. 3. REQUIRED FINISH AND FORM ACCURACY We use abrasive products such as grinding wheels because of their speed, ability to repeat form, and achieve finish. When trying to select the correct wheel specification, we need to look at the operation and establish whether we are looking for rapid stock removal or a finer finish. Whether the part is simple/flat or if there is a form to hold. Knowing these requirements will help us select the correct grinding wheel for the process. Again, we need to consider the required surface finish, dimensional tolerances, form holding requirements, and stock removal rates. By examining these, we can determine the appropriate grit size. What we need to achieve with the wheel will also help us determine the grade of bond or hardness of the wheel. For low Ra finishes and/or close geometric tolerances, we naturally want to use a finer grit because the actual grit size of the grain provides for more points of contact between the work and wheel. This helps with precision finishes, which have a shallower scratch pattern, resulting in a lower micro-inch finish. It is also the physical size of the grain that allows us to achieve and hold small radius and complex forms better than we could with larger or coarser grit sizes. When we require fast stock removal rates or when form and finish are not as critical, we want to use a coarse grit size. Whether we need a specific finish or form, we always want to use the coarsest grit size we can. A coarser grit will take a larger chip, and as such, increase stock removal cutting cycle time. When we need close geometric accuracy and form holding, we need to use a harder grade. Going as hard as we can allows the wheel to hold the profile/form longer, as well as ensuring the grains are held long enough to achieve the desired results. This next comment may seem conflicting, but when we want finer finishes and higher stock removal, we can use a softer bond. A wheel with a softer bond will easily release dull grains and keep newer sharp grains in contact with the material. This in turn means that sharper grains are continually exposed to the work, increasing stock removal as well as helping with the required finish by preventing dull abrasives from rubbing and burning the part. Although the actual finish is more a factor of grit size, keeping sharp grain in the grind zone helps provide the required finish. The final aspect of the wheel spec determined by looking at the part requirements is the bond type. When we require close tolerances and form holding, we will want a vitrified product. Vitrified wheels hold their form/shape better than organic or resin bonded wheels, but organic bonds tend to finish better. For reflective and other finer finishes, the operation should consider using an organic or resin bond. Organic bonds, unlike vitrified bonds, have a little give to them and some of the grinding forces are going into the wheel/bond, reducing the chip size. Another benefit of using an organic bond for fine finish grinding is that organic bonded wheels break down from the heat of the grind, and they tend to hold the grain a little longer, allowing it to run and dull. It is this dulling and rubbing that helps generate the finer finish. 4. AREA OF CONTACT Area of contact, the forth factor we consider, is in part related to the second factor: severity of operation, in that it considers the amount (or area) of contact between the work and the wheel. This factor looks at how the force applied to make a chip will be distributed through the grind zone in much the same way surface area is related to pressure in a hydraulic system. When a wheel is applied to the work, the force applied is distributed over all the cutting points in the grind zone. The larger the area of contact, the lower the force per gain. Conversely, the smaller the area, the higher the force per grain. When we have a small area of contact, we would want a tough/durable grain. A small area of contact equates to a higher force per grain, so we need an abrasive grain that can hold up to these forces without fracturing too early and suffering premature wear. Again, when the force per grain is higher due to smaller contact areas, a ceramic or superabrasive grain may be a good choice. Knowing we have a small area of contact, we will want to use a finer grit size because in addition to providing more abrasive points at the area of contact, it will also ensure that the relative pressure or grinding forces will be split among many grains. A smaller area of contact typically also calls for using harder graded wheels. Because the forces are higher in smaller areas of contact, we need the wheel to hold its shape and not release grains too soon. Since the relative grinding pressure at the point of contact would be high, a harder grain is used to prevent premature wheel wear. When the area of contact increases and becomes larger, like that of a blanchard segment, we need a milder, more friable grain. Due to the increased number of grain in contact with the work in the grind zone, the force per grain is lower and the grain can fracture and self-sharpen more easily. In operations with a large area of contact, we want a coarser grit so that the grinding forces (which would be lower because the area is large) are spread over fewer grains, thus increasing the pressure per grain so that work can be done more efficiently. The forces will help the grain penetrate the work and assist in making the grain breakdown/fracture as needed. In operations with large areas of contact, we run the risk of dulling the grain. This is due to the lower force per grain we typically see in operations with a large area of contact. To offset the possibility of burning related to dulling grains, we want a softer grade for our wheel so the grain can be released and replaced before any damage is done to our part. The final factors, although important, only help fine tune or narrow down the wheel specification options. 5. WHEEL SPEED The fifth factor to consider is the wheel speed. We have to consider the operating speed of the wheel in surface speed. To calculate surface speed, use these equations or try our iGrind app . Wheel speed determines what bond type is most suited for the required speed or if a special high speed bond might be required. As a general rule: For surface speeds of 8500 SFPM (43 M/s) and below, either a vitrified or an organic bond can be used; although, most common vitrified wheels are designed for 6500 SFPM (33 M/s) and lower. For surface speeds over 8500 SFPM (43 M/s), we usually recommend an organic bond be used for safety reasons. We should note though that some of today’s newer vitrified bonds can run at speeds over 8500 SFPM (43 M/s) but typically require a special rating. One final note on wheel speed. Wheels will act differently based on their speed. It is a commonly accepted practice that for every 1000 SFPM (5.08 M/s) the surface speed changes, the wheel will act one grade harder or softer depending upon how the speed changes. Slower = Softer. At slower wheel speeds, there is a higher force per abrasive particle causing the grain and/or bond to break down quicker. Faster = Harder. At higher wheel speeds, there is lower force per abrasive particle making both the grain and bond seem more durable and resistant to breaking down as designed. This can be useful in troubleshooting a wheel specification and/or to dial in the wheel grade. 6. COOLANT USE The sixth factor we consider is coolant use. Coolant in a grinding system affects vitrified and organic (resin) bonded wheels differently and is considered when determining the wheel's grade or hardness. If Coolant is Used: Vitrified bonded wheels will act softer because the lubricity of the coolant helps reduce the friction/energy in the grind zone, which can help keep the grain from dulling. This keeps it sharper and freer cutting. Organic (resin) bonded wheels will act harder because the coolant reduces the heat in the grinding zone. It is the heat of the grind that softens the wheel, allowing it to self-sharpen; if the heat is eliminated or reduced, the wheel will not break down as designed. If No Coolant Used: In dry operations, vitrified bonds will act harder because the grain will rub and dull more, creating more heat in the grind zone and potentially leading to burning and/or other damage. Organic (resin) bonded wheels will act softer due to the ways in which the bonds work. More heat in the grind zone will soften the wheel quicker, possibly leading to early wheel wear and premature life. 7. MACHINE/SPINDLE HORSE POWER The seventh and final factor to consider is horse power. We have to consider the horse power of the grinding machine to determine the grade of the bond or hardness of the wheel. High Horse Power – When a machine has a higher horse power available at the spindle, we should use a harder wheel grade. We make the wheel harder so it will hold form and hold on to the grain as long as possible under the higher power/force conditions. We can also use a more durable grain knowing there should be sufficient force/energy available to fracture the grain and get it to self-sharpen. Low Horse Power - We know that grinding energy causes the wheel and abrasive grains to break down and perform as designed. When the machine is low power or is under powered at the spindle, we may not be able generate enough force to break the wheel down as needed, resulting in grain dulling leading to burn and other surface damage. To mitigate this, we need to use a softer grade for our wheels. We may also want to look at more friable grains to help with this. As you can see, there are several things to consider when trying to determine a starting specification for a grinding wheel. There may be situations when one factor may point you in one direction, while a second may point you in the opposite direction. In cases like that, it is best to look at where the majority of the factors are pointing you and/or to consider what you feel are the most important factors of your operation and use those factors to determine where to start. The chart below lays out all of the factors on a single sheet, making it easier to reference. All seven are listed along with their considerations and what aspects of the wheel specification they affect. FACTORABRASIVE TYPE & CHARACTERISTICGRIT SIZEGRADEBOND TYPE 1. MATERIAL BEING GROUND Consider the material's properties (Metal/[Ferrous/Non-Ferrous] or Non-Metal, Hardness, Grindability, Etc.)Ferrous Metals: AI-O or cBN Non-Ferrous/Non-Metal: SiC or Diamond Easy to Grind: Tough/Durable Grain Hard to Grind: Mild/Friable GrainEasy to Grind: Coarser Grit Hard to Grind: Finer GritEasy to Grind: Harder Grade Hard to Grind: Softer Grade 2. SEVERITY OF OPERATION Consider the force per grain, grinding pressure in the grind zoneHeavier Pressure: Tough/Durable Grain Lighter Pressure: Mild/Friable GrainHeavier Pressure: Coarser Grit Lighter Pressure: Finer GritHeavier Pressure: Harder Bond Lighter Pressure: Softer Bond 3. REQUIRED FINISH AND/OR FORM ACCURACY Consider the required surface finish, dimensional tolerances, form holding, and stock removal requirements Higher Stock removal, Basic Form and/or Rougher Finish: Coarser Grit Size More Complex Form, Close Tolerance and/or Finer Finish: Finer Grit SizeMore Complex Form, Close Tolerance and/or Better Form Holding: Harder Grade Higher Stock Removal and/or Finer Finish: Softer GradeBetter Form Holding: Vitrified Bond More Reflective/Better Finish: Resin Bond4. AREA OF CONTACT Consider the amount or area being contacted between work and wheel in the grinding zoneSmall Area of Contact: Tough/Durable Large Area of Contact: Mild/FriableSmall Area of Contact: Finer Grit Large Area of Contact: Coarser GritSmall Area of Contact: Harder Grade Large Area of Contact: Softer Grade 5. WHEEL SPEED Consider the required/desired wheel speed in surface speed (SFPM = 0.2618 x Whl Dia x Spindle RPM)For every 1000 SFPM a wheel speed changes UP and DOWN, the 'effective' grade of the wheel changes harder (faster) or softer (slower). This can be useful when troubleshooting or "dialing in" a wheel specification.For speeds of 6500 SFPM or lower: Vitrified (Vitrified can run up to 8500 SFPM under certain conditions) Speeds over 8500 SFPM: Organic/Resin6. COOLANT USE Consider whether or not coolant will be usedFor Vitrified Wheels, we consider the material and its effects on the material For Organic/Resin, we consider the wheelIf coolant is used: Vitrified: Can go 1 grade harder Organic/Resin: Should go one grade softer 7. MACHINE/SPINDLE HORSEPOWER Consider the available spindle power of the grinder/operationSpindle Motor Sizing: BALLPARK - 15 to 20 HP per inch of wheel widthHigh HP: Harder Grade Low HP: Softer Grade NOTE: When deciding on a wheel specification for a particular operation, all factors need to be considered; however, it is possible that they may conflict. If that should happen, it is important to use any key factor(s) to determine the final starting specification. Related / Latest Stories Tips for Improved Surface Grinding Create the most productive surface grinding process with these grinding wheel selection and parameter recommendations. Read more 5 Grinding Considerations for Improving Surface Finish See how making adjustments to operational parameters, wheel dressing, grit size, coolant delivery, and machine condition can improve surface finish. Read more 5 Reasons to Upgrade to Vit-cBN Learn when to upgrade your cylindrical grinding process and what factors to consider when making the switch from a conventional vitrified wheel to a vitrified cubic boron nitride, or vit-cBN, wheel. Read more

Two super-hard materials which are commonly used in industrial processing are diamond and cubic boron nitride. After a series of processing procedures, these two super-hard materials can be made into various tools or used directly in various devices. Here we focus on one application, the diamond grinding tool. What Is a Diamond Tool? A diamond tool is a cutting, grinding or polishing tool with diamond grains fixed on the working parts of the tool via some kind of bond material or by some other special means. Diamond tools are used for cutting, grinding, and drilling. Diamond is also used as an abrasive material for polishing stone, concrete, ceramics, bricks, glass, fire-proof materials and other similar hard materials. Because diamond is made of carbon, it can dissolve into steel or iron, leading to tool wear and work hardening, so should not be used for cutting workpieces made of these materials. Cubic boron nitride can be used for these types of applications. There are two types of diamonds: natural and man-made. It is the hardest substance among known materials and has the strongest ability to refract light, so large-grained natural diamonds have long been the known as the "king of gems". Diamond also has the highest strength, thermal conductivity, and velocity of sound transmission among known materials. It has a small sliding friction coefficient, high chemical and thermal stability and is highly hydrophobic. It is widely used in sawing tools, drilling tools, super-hard tools, dressing tools and wire drawing dies. Diamond abrasive can be used along with binders made of metal powder, resin powder, ceramic and/or electroplating metals to form a circular grinding tool called a diamond grinding wheel. The diamond grinding wheel is generally composed of a working layer and a transition layer. The working layer, also known as the diamond layer, is composed of abrasives, and is the working part of the grinding wheel. The transition layer is composed of binders and fillers that firmly connect the diamond layer to the base substrate. The quality and accuracy of the grinding wheel depend a lot on the matrix. A diamond grinding head is often used for non-metallic materials such as stone and ceramic materials. It is fixed onto the base of the body of the grinding tool. New types of tools are being developed that have high grinding performance, simple manufacturing, low cost, and are suitable for large-scale grinding. A new type of manufacturing process has been developed that uses artificial diamond and cubic boron nitride as raw materials to make flexible, coated abrasive tools. These flexible, super-hard abrasive products include: abrasive belts, sand sleeves, sand discs, sand sheets, sponge hand wipes and other forms. Flexible diamond and cubic boron nitride products are widely used for grinding and polishing stone, glass, ceramics, synthetic materials, cemented carbide, non-ferrous metals, iron-based alloys and other hard materials. Due to its high hardness and high single-piece compressive strength, super-abrasives have the advantages of high grinding efficiency, low grinding temperature, good workpiece surface quality, and stable grinding performance. Diamond abrasive belts have been proven to be very cost-effective for processing of automotive glass and high-grade glass. It has better grinding force, chip removal and heat dissipation than traditional diamond grinding belts. Diamond sawing tools include various saw blades such as circular saw blades, gang saws, band saws, wire saws, etc. They are mainly used for cutting non-metallic materials such as marble, granite and concrete. Drilling tools mainly include synthetic diamond geological drill bits, oil (gas) well drill bits, and engineering thin-wall drill bits, which are respectively used for geological exploration, oil (gas) exploration and exploitation. Synthetic diamond geological drill bits are some of the most important tools used in industrial applications and for drilling holes in building walls and foundations. Drill bits can be roughly classified into: core drill bits, full-section drill bits, and engineering drill bits. Among them, the most widely used is the geological exploration core drill, which can be divided into impregnated drill bits and surface inlaid drill bits. They are manufactured using hot pressing, dipping, cold pressing, sintering, and electroplating.

In the context of lapidary work, "cabbing" refers to the process of shaping and polishing gemstones into caboc ons. A cabochon, commonly referred to as a "cab," is a gemstone that has been shaped into a smoothly rounded, convex top with a flat or slightly domed base. During the cabbing process, lapidaries use specialized tools and techniques to transform rough gemstone material into finished cabochons. The term "cabbing" can have different meanings depending on the context. Here are a few possible interpretations: 1. Cabbing as a Transportation Service: In some regions, "cabbing" refers to using a taxi or cab as a mode of transportation. It typically involves hiring a taxi to travel from one location to another, with the fare being based on distance or time. 2. Cabbing in Gemology: In the field of gemology, "cabbing" or "cabochon cutting" is a technique used to shape and polish gemstones. It involves creating a smooth, rounded, and convex surface on a gemstone without any facets. 3. Cabbing in Geology: In the context of geology, "cabbing" may refer to the process of cutting and shaping rough rocks or minerals into cabochons for use in jewelry or display. This involves grinding and polishing the material to create a smooth and rounded surface. 4. Cabbing as a Slang Term: In some informal contexts, "cabbing" can be used as slang to refer to avoiding or skipping an event or commitment. It can imply the act of canceling plans or avoiding participation in a particular activity. The precise meaning of "cabbing" can vary depending on the industry or region where it is used. If you provide more specific context, I can provide a more accurate explanation. The process typically involves the following steps: Rough Shaping: Lapidaries start by shaping the rough gemstone into a basic form, removing excess material and creating a general outline of the desired cabochon shape. This step is often done using saws or grinding equipment. Beveling: Once the rough shaping is complete, lapidaries may add beveled edges to the cabochon. Beveling involves creating angled edges around the perimeter of the stone, enhancing its appearance and adding depth. Sanding and Smoothing: Lapidaries progress to sanding the cabochon, using successively finer grits of sandpaper or diamond abrasive pads to refine the shape and remove any scratches or imperfections. This process gradually smooths the surface of the stone. Polishing: The final step is polishing the cabochon to achieve a glossy, lustrous finish. Lapidaries use polishing wheels or pads charged with polishing compounds or abrasive materials. The cabochon is carefully held against the rotating wheel or pad, allowing the compound to buff and polish the stone's surface. The result of the cabbing process is a polished cabochon that showcases the gemstone's colors, patterns, and natural beauty. Cabochons are widely used in jewelry making, decorative arts, and as collectible gemstones.

Lapidary equipment refers to the tools and machinery used in lapidary work, which involves the cutting, shaping, polishing, and engraving of gemstones and minerals. These specialized tools enable lapidaries to work with various types of gemstone materials and transform them into finished pieces. Here are some common types of lapidary equipment: Lapidary Saw: A lapidary saw is used for cutting gemstone rough into smaller pieces or specific shapes. It can be a trim saw, slab saw, or band saw, and it utilizes diamond-edged blades or abrasive discs for cutting. Cabbing Machine: A cabbing machine, also known as a cabochon machine, is designed specifically for shaping and polishing gemstones into cabochons. It typically consists of grinding wheels, polishing wheels, an adjustable platform, and a motor for rotation. Faceting Machine: A faceting machine is used for precision cutting and shaping of gemstones with multiple facets. It allows lapidaries to create faceted gemstones with specific angles, facets, and proportions. Faceting machines have various components like the mast, dop sticks, and index gears. Grinding and Polishing Wheels: These wheels are used in various lapidary machines, such as cabbing machines and faceting machines, for grinding and polishing gemstones. They come in different grit sizes to achieve different levels of coarseness or smoothness. Tumblers: Lapidaries use tumblers for the process of tumbling, which involves polishing and smoothing gemstones. Tumblers consist of a barrel or drum that rotates, along with abrasive materials and water or polishing compounds, to create a tumbling action that polishes the stones. Engraving Tools: Engraving tools are used for carving designs or patterns onto gemstones. These tools can be handheld gravers, micro-engravers, or rotary tools with diamond or carbide tips. Calipers and Gauges: Precision measuring tools like calipers and gauges are essential for accurate gemstone measurements and evaluations. They help lapidaries assess the dimensions, proportions, and symmetry of gemstones. Safety Equipment: Safety equipment is crucial in lapidary work to protect the lapidary from potential hazards. This may include safety glasses, protective gloves, dust masks, and aprons. These are just a few examples of lapidary equipment used in the industry. The specific tools required may vary depending on the specific lapidary processes, such as cutting, shaping, polishing, or engraving, as well as the lapidary's preferences and expertise.

Cabbing in lapidary refers to the process of shaping and polishing gemstones into cabochons. A cabochon, commonly referred to as a "cab," is a gemstone with a smoothly rounded, convex top and a flat or slightly domed base. The cabbing process involves several steps: Rough Selection: Lapidaries begin by selecting a suitable piece of rough gemstone material. This can be sourced from mines, gemstone suppliers, or collected by lapidary enthusiasts. Shaping: The rough gemstone is shaped into the desired cabochon form. Lapidaries use various lapidary tools, such as a cabbing machine, grinding wheels, and shaping equipment, to gradually shape the gemstone. This involves removing excess material and forming the stone into a smooth and symmetrical shape. Beveling: After the rough shaping is complete, lapidaries may add beveled edges to the cabochon. Beveling creates angled edges around the perimeter of the stone, enhancing its visual appeal and adding depth. Sanding: The lapidary progresses to sanding the cabochon, starting with coarser grits and gradually moving to finer grits. Sanding materials, such as sandpaper or diamond abrasive pads, are used to refine the shape, remove scratches or imperfections, and achieve a smoother surface. Polishing: The final step is polishing the cabochon to bring out its natural luster and create a glossy finish. Lapidaries use polishing wheels or pads charged with polishing compounds or abrasive materials. The cabochon is carefully held against the rotating wheel, allowing the compound to buff and polish the stone's surface to a high shine. Throughout the cabbing process, lapidaries employ their expertise and artistic vision to shape the stone and highlight its best features. They assess the gemstone's shape, symmetry, and smoothness, making adjustments as necessary. The result is a beautifully polished cabochon that can be used in jewelry, decorative pieces, or as collectible gemstones. Cabbing is a popular technique in lapidary work, allowing lapidaries to transform rough gemstones into attractive and versatile cabochons. It requires skill, precision, and an understanding of the gemstone's characteristics to create cabochons that showcase the stone's natural beauty.

A cabbing machine is a piece of lapidary equipment specifically designed for shaping and polishing gemstones into cabochons. It is a specialized tool used by lapidaries, jewelers, and gemstone enthusiasts to create smoothly rounded, convex top gemstones with a flat or slightly domed base. A typical cabbing machine consists of the following components: Grinding Wheels: Cabbing machines are equipped with grinding wheels that come in various sizes and grits. These wheels are made of abrasive materials, such as diamond or silicon carbide, and are used to shape the gemstone by removing excess material. Water Cooling System: Many cabbing machines have a water cooling system to prevent overheating during the grinding process. Water is continuously sprayed onto the grinding wheels to lubricate them and keep the gemstone cool. Motor and Drive System: Cabbing machines are powered by an electric motor that rotates the grinding wheels at a controlled speed. The motor is connected to a drive system that ensures smooth and consistent rotation. Adjustable Platform: The gemstone being worked on is placed on an adjustable platform that allows the lapidary to control the angle and position of the stone in relation to the grinding wheels. This enables precise shaping and control over the cabochon's symmetry. Polishing Wheels: Cabbing machines also include polishing wheels or pads made of materials such as felt or leather. These wheels are used in the final stages of the cabbing process to achieve a high polish on the gemstone's surface. Splash Guard: A cabbing machine may have a built-in splash guard or shield to contain water and debris during the grinding and polishing process. This helps keep the workspace clean and minimizes the risk of injury from flying particles. Cabbing machines offer a controlled and efficient way to shape and polish gemstones, ensuring consistent results and professional-quality cabochons. They are widely used by lapidaries and jewelry makers to create cabochons for use in various applications, including jewelry, decorative objects, and collectibles.

The difference between a 6-inch and an 8-inch cabbing machine lies primarily in the size of the grinding and polishing wheels they accommodate. Here are some key distinctions between the two: Wheel Size: The main difference is the diameter of the wheels used for grinding and polishing. A 6-inch cabbing machine has grinding and polishing wheels that are 6 inches in diameter, while an 8-inch cabbing machine has wheels with an 8-inch diameter. The larger wheel size of the 8-inch machine provides a wider grinding and polishing surface area. Surface Area: The larger wheel size of the 8-inch cabbing machine offers more surface area for grinding and polishing gemstones. This can be advantageous when working with larger or irregularly shaped stones, as the wider surface area allows for better control and coverage during the cabbing process. Handling Different Sizes: The 8-inch cabbing machine can handle larger stones more effectively due to its larger grinding and polishing wheels. It can accommodate a wider range of stone sizes and shapes, providing more versatility in the lapidary work. However, the 6-inch cabbing machine is still capable of working with various sizes of gemstones, albeit with a slightly smaller surface area. Weight and Stability: Due to the larger wheel size and potentially larger motor, an 8-inch cabbing machine may be heavier and more stable compared to a 6-inch machine. This additional weight can contribute to increased stability during the cabbing process, reducing vibration and improving overall control. Cost: Generally, an 8-inch cabbing machine tends to be more expensive than a 6-inch machine due to the larger size and materials required for construction. The price difference may vary depending on the specific brand, model, and additional features of the machines. When choosing between a 6-inch and 8-inch cabbing machine, consider the size of the gemstones you typically work with, your budget, and the level of versatility and stability you require. The larger wheel size of the 8-inch machine may be advantageous for those working with larger stones or needing more surface area, while the 6-inch machine can still be suitable for smaller to medium-sized cabochons and may be more cost-effective.

Choosing the best faceting machine is a very challenging and very personal decision. You first need to assess the various qualities of different machines and then decide which factors are most important for your faceting experience . Qualities Let's define each of these qualities before looking at machines: repeatability, reliability, speed, accuracy, cost, and availability. Repeatability This means that every time you cut a stone, the same actions produce the same effect. You don't have to reinvent the wheel every time you want to cut a round brilliant. Repeatability also means there's some sort of reference point to help guide you towards cutting. Reliability This means that if you buy a new machine, you'll still have a working machine in 1 year, 5 years, 10 years, and, hopefully, 20 years and beyond. Most faceting machines have a long life if you take care of them. Reliability also includes accuracy over the life of the machine and its included accessories. Speed This means how fast you can cut a stone. When comparing faceting machines, we're going to see that the biggest challenge is the compromise between speed and accuracy. Accuracy This means how well the machine helps you cut a perfect stone. We use faceting machines because creating straight faces on a rock while holding it in our hand is very hard. Cost In addition to speed and accuracy, cost will probably be one of your main deciding factors. Cost tells us how much money we have to pay for a new machine, including shipping, import taxes, and accessories. Availability Some of the best machines ever invented can no longer be purchased because they're no longer made. This will factor into your decision, because buying used is a completely different game with a different set of risks than buying new. In nearly all the examples in this article, we'll assume you're buying a brand new machine from the manufacturer, because any other type of comparison would be unfair. Types of Machines To sum up 500 years of gem cutting technology , let's place the modern incarnations into three different categories: the mast machine, the jam peg machine, and the hand piece machine. The Mast Machine This type of machine comes from countries that have grown up with competition cutting cultures, namely the United States, Australia, and Russia. These machines are by far the most accurate types for cutting stones and, typically, the most expensive. Unfortunately, speed heavily compromises the accuracy of these machines. Mast machines are slower and less forgiving compared to other machines. They're fairly easy to learn on and are great for the hobbyist cutters. However, they're completely unsuitable for production/speed cutting. The Jam Peg Machine These are the most traditional types of cutting machines, though not all jam pegs are created equally. Because they're the fastest, these machines are the best for production but they sacrifice accuracy. Although, depending on the technique, jam peg machines can be very accurate, they're generally less all-around useful and take a long time to master. The Hand Piece Machine In my opinion, the hand piece machine makes the perfect compromise between the mast machine and the jam peg. Compared to the best jam peg machine, the hand piece machine will be more accurate, more repeatable, and more precise. Compared to a mast machine, the hand piece machine will always be quicker and more adaptable in operation, because you can easily move the hand piece around to get the best view of your stone while cutting. Also, from a production point of view, it's very easy to take the stone out and put it back in the hand piece or to hand off the hand piece from the cutter to the polisher in a cutting factory. If it hasn't become clear yet, my bias over the last few years has moved from mast machine to hand piece machine as I've gained more exposure to them. I believe the hand piece provides the best compromise between all the quality factors. However, I will remain as unbiased as I can while reviewing each machine in this article. Mast Machines Ultra Tec V-2/V-5 The Ultra Tec is probably the most well-known faceting machine in the world. Though frequently considered the best machine, every faceter who has ever lived has debated its merits. The V-5 machine features a digital readout that tells you exactly what angle you're cutting, and many people love this feature. Over the years, Ultra Tec has upgraded various parts of the machine while still remaining backwards compatible and upgradable. The current incarnation of the machine has a beefy mast that resists flex and, in general, lives up to its reputation of being a great machine. It's also the most expensive machine you can currently buy. You can easily find many working used machines from the 1980s, which tells us that this machine will probably be cutting stones long after you retire. The customer service at Ultra Tec can be hit-and-miss, and it seems that every single part of the machine is proprietary, which means that if something breaks you must order it from the company. Many of these small parts, including nuts and bolts, aren't as cheap as those from other manufacturers. Cost: $4,950 (plus shipping from USA) Availability: Order from manufacturer at ultratec-facet.com Specs: ultratec-facet.com/PDFs/Plist.pdf Facetron Another popular machine for gem cutters, the Facetron doesn't offer any of the high-tech features other manufacturers have introduced. Nevertheless, it's considered a very reliable machine. The depth gauge helps make cutting fast and repeatable, and I've seen some of the best stones in the world cut on this machine. It has a more affordable price than the Ultra Tec but with fewer 21st-century features. It's reliable, and many cutters keep the same machine for their whole cutting life. Cost: $3,495 (plus shipping from USA) Availability: Order from manufacturer at facetron.com Specs: facetron.com/facetron/ Graves Mark IV/5XL The Graves Company is one of the oldest American manufacturers of faceting machines. These machines have seen a number of improvements over the years. With the release of the Mark 5XL, it now offers a well-designed digital angle readout at a very low price. Generally, faceters hold Graves machines in high regard due to their cost and the fact that they work well. In recent months, there have been problems with the Graves Company. Many people have advised against ordering from the company, since fulfilling orders may take up to 6+ months. If you can find a new machine from a dealer, that will be your best option. Cost: $1,795 (plus shipping from USA) Availability: Slow shipping from gravescompany.com Specs: gravescompany.com/Mark-5XL-Faceting-Machine.html Poly-Metric Scintillator This machine gives the Ultra Tec a run for its money. The Scintillator boasts a digital display for precise cutting angles as well as a depth gauge similar to the Facetron's, which helps you cut a whole tier of facets to the same depth quickly. The mast is beefy, and the quick release button on the mast head means that if you want to jump up and down the mast to go from girdle to crown angle, you don't have to crank it for 5 minutes. The whole machine has a strong industrial feel and is made well. The company is very easy to deal with, and the machine is reasonably priced if you need parts or maintenance. Due to its nearly all-metal construction, this is probably the heaviest mast-style faceting machine available. If you need to travel with the Scintillator, it may pose some challenges. Cost: $3,995 (plus shipping from USA) Availability: Order from manufacturer at polymetricinc.com Specs: polymetricinc.com/scintillator88.htm Facette GemMaster II It's hard to talk about the GemMaster II at this stage, because the machine was discontinued. However, the company now has a new owner, and the machines will soon be available again. The GemMaster II is like the holy grail of faceting machines. They're rare, unusual, and seem to imbue their users with a certain spiritual enlightenment that allows them to cut very nice stones quickly. The GemMaster is hardly a mast machine, with its unique radial arm that the quill slides along. The machine also has a electric depth gauge (similar to a BW Meter) that tells you how close you are to your desired angle. The machine is said to be very fast and easy to use. Many who have learned on them refuse to use any other type of machine. When the new version of the GMII comes out, we'll see if it lives up to its reputation. These machines have only been available on the used market, but very soon you'll be able to order the new incarnation from the manufacturer. Cost: $5,999 Availability: Coming soon to fac-ette.com/index.php Specs: fac-ette.com/gemmaster/gemmaster VJ Faceting Machine This seems to be the Australian equivalent of the GemMaster II. I haven't used or seen this one, so I'll copy the following from their website: Used by the most discerning faceters around the world. A different concept offering unparalleled and repeatable accuracy and ease of operation. Suitable for all levels of faceting experience from Beginners to Commercial and Competition Faceters. No moving columns. Direct reading angle scale to one-tenth of degree without vernier. From girdle to table without moving the dop from the hand piece. Minimum vertical movement of stone when changing angles. Will take 6" or 8" laps. Cost: vjfacet.com/VJ_Price_List.pdf (plus shipping from Australia) Availability: Order from manufacturer at vjfacet.com Specs: vjfacet.com/Products_VJ_Facet.html Jam Peg Machines Adlap The French developed this type of jam peg (known as Évention in French) with the mechanical stick, and this is their latest version. The machine boasts an electric motor (as opposed to the traditional hand crank). The head has 17 or 33 notches, giving you a wide range of preset angles. If you need to go in between the preset angles or "cheat" slight left and right, there are knobs on the head to move to peg holes in both directions. The strength of this machine lies in its speed, due to the mechanical stick that allows you to cut facets very, very quickly. The manufacturer also offers courses to help you learn how to cut on this machine. Once you learn to use it, the Adlap is the fastest machine you can buy. A master will be able to cut facets very, very exactly, though becoming proficient can take years instead of the months it might take on a mast-type machine. Cost: €3,290 (shipping from France) Availability: Order from manufacturer at taille-pierre-precieuse.com Specs: translate.google.fr/translate?hl=en&sl=fr&u=http://taille-pierre-precieuse.com/metier.html&prev=search Somsit This is the Thai version of the French machine. The main advantage of this machine is that it's dirt cheap. The accuracy is lower than the French-made one, and the machine is very heavy since it's built into a table and requires a separate free-standing motor to run. The index wheel that allows for quick cutting is made of plastic instead of metal, but the price seems to make up for it. Cost: $250 (head + stick is $25 if you put it on your own homemade table) Availability: Purchase from manufacturer in Bangkok at somsit.com Specs: somsit.com/product/detail/73/18 Bhandasa The Israelis took the French jam peg and took it to the next level of innovation. They made the whole head beefier and added 64 teeth to the mechanical stick, so you can cut 8 facets against the index on the mechanical stick very quickly and then very accurately move the stone 1-4 teeth around the index to quickly cut star or girdle facets. Cost: $? (shipping from Israel) Availability: Purchase from manufacturer at bhandasa.com Specs: bhandasa.com/2040%2DFaceting%2DStraight%2DGirdling%2DCut%2DPolish%2DMachine.html Hand Piece Machines Imahashi Imahashi originated this style of desktop hand piece faceting machine. The machine uses a well-designed hand piece to allow the cutter to control angle and index while also allowing "cheating" by adjusting the height of the feet of the hand piece. This machine has a great reputation and is easy to learn and use. They have two different types of hand pieces, one which has a cam built into it for perfect preforming and a normal one that just cuts at angles. The metal plate that the hand piece sits on moves up and down to control the depth of cut by turning the brass knob at the top of the riser plate handle. The downside of this machine is the price. Cost: approx. $4,000 (shipping from Japan) Availability: Purchase from manufacturer at imahashi.net Specs: imahashi.net/e-img/FAC-8.pdf Raytech Shaw The concept of this American-made machine is similar to other hand piece designs but executed a little differently. This machine sits sideways compared to other hand piece bases. The hand piece is the lightest of any I've seen. The tradeoff is it also seems a little less substantial and industrial. I have heard complaints that after the machine has seen some use, the dop starts to wobble inside the quill, causing problems with flat polishing. This might only occur with certain machines, though. On the machine, the riser plate goes up and down via a spinning wheel underneath the riser plate, so there's no pole to potentially hit your stone against. Cost: $1,949 (shipping from USA) Availability: Purchase from manufacturer at raytechshaw.com Specs: raytechshaw.com/features.html Sterling The Sterling machine is the latest development in hand piece machines from Sri Lanka. They offer different hand pieces for different purposes: some with cheaters, some for small hands, and some just standard. This is a well-made, heavy-duty workhorse of a machine and can easily run in a production environment all day for decades. It has the ability to cut stones quickly and with great accuracy. Cutting perfectly accurate stones isn't as easy as with a mast-style machine, but once you master the art of cheating by adjusting foot height, you can match mast accuracy. This machine will cut light years faster than any mast machine I've tried. I've seen a master cutter facet five 20-ct precision-cut stones on this machine in one day. Cost: $1,200 (shipping from Sri Lanka) Availability: Purchase from manufacturer at sterlinggemland.com Specs: sterlinggemland.com/products.php Bunter If we're talking about the best faceting machines, I couldn't resist putting this on the list. Lets get the Cons out of the way first. The machine costs around $10,000 used (including accessories and laps) and isn't available anymore. It's also incredibly heavy and uses its own special laps and dops, which are also incredibly heavy. Now for the Pros: this is the best faceting machine ever made. I'll leave it at that. The Bunter was made with Swiss precision for cutting big and small stones with tight tolerances for the watch industry. The vertical lap means that the stone is right in your face all the time, so you can see it easily. Separate cutting and polishing wheels mean that you never switch laps, so you save time. Amazing and light, the hand piece design can do anything, including cheating and doing girdles and tables with no adapters. The machine is so well-made that the manufacturers basically put themselves out of business, because once you buy one it never breaks, so they never made money again. If you ever see one of these, just buy it and practice. You won't regret it. Cost: $5,000-10,000 (shipping from Switzerland) Availability: Manufacturer doesn't produce anymore, purchase used in Geneva at bunter.ch Specs: youtube.com/watch?v=GJA1rusGjS4 Conclusion The real question isn't which is the best faceting machine but what's the best machine for your needs. I think most people asking this question are only considering mast-style machines, so I included other types in this article in hopes that they broaden the minds of new cutters. One thing to make clear is that each machine has its own traditions and techniques, and they aren't always that interchangeable with each other. Sometimes, if you don't understand one machine's technique, you might think it's not any good, so I guess the final question a cutter must ask is "Who is my teacher and what techniques can they show me?" I currently use a Poly-Metric Scintillator and a Bunter machine at home and a Sterling machine at work. I have cut a stone on most of the machines listed here. My conclusion is that a hand piece-type machine is the most fun to cut on, and it's also faster, which means you can cut more stones per week. I also think you could win a competition with a hand piece machine, though it might mean a little bit more sweat. I have gone from using an Ultra Tec to using and loving the Poly-Metric to using and adoring the Sterling machine. It's a great machine to use and an especially great machine to learn on because it's simple and easy to use.

The process of cutting and polishing gems is called gemcutting or lapidary , while a person who cuts and polishes gems is called a gemcutter or a lapidary (sometimes lapidarist). Gemstone material that has not been extensively cut and polished is referred to generally as rough . Rough material that has been lightly hammered to knock off brittle, fractured material is said to have been cobbed . Rough corundum . All gems are cut and polished by progressive abrasion using finer and finer grits of harder substances. Diamond, the hardest naturally occurring substance, has a Mohs hardness of 10 and is used as an abrasive to cut and polish a wide variety of materials, including diamond itself. Silicon carbide, a manmade compound of silicon and carbon with a Mohs hardness of 9.5, is also widely used for cutting softer gemstones. Other compounds, such as cerium oxide, tin oxide, chromium oxide, and aluminum oxide, are frequently used in polishing gemstones. Lapidary Techniques Several common techniques are used in lapidary work: sawing grinding sanding lapping polishing drilling tumbling Using the techniques listed above, gemstones are typically fashioned into one of several familiar forms: cabochons faceted stones beads and spheres inlays intarsias and mosaics cameos and intaglios sculptures Sawing Sawing a piece smoky quartz. (Warning! Holding rough by hand during sawing can be hazardous to the stone, the saw, and the cutter! Extreme caution is required.) In most gem sawing, a thin circular blade usually composed of steel, copper, or a phosphor bronze alloy impregnated along the outer edge with diamond grit and rotating at several thousand surface feet per minute literally scratches its way through a gemstone. A liquid such as oil or water is used to wash away cutting debris and keep the stone and the sawblade from overheating, which could cause damage to both the stone and the sawblade. Several sizes of circular rock saws are frequently used by most gemcutters: A slab saw , typically 16 to 24 inches in diameter, is used to cut stones of several inches thickness into relatively thin slabs (often 1/8 to 3/8 inch thick). A trim saw , typically 6 to 10 inches in diameter, is used to cut smaller stones into thin slabs or to cut small sections out of slabs. A faceter's trim saw , typically 4 inches in diameter, is used with a very thin blade, to saw small pieces of expensive rough. There are also jigsaws that employ either a reciprocating wire or a continuous thin metal band. These are useful for cutting curved lines that are impossible with circular saws. They are also useful in minimizing waste on extremely valuable rough material. Back to techniques. Grinding Grinding , usually with silicon carbide wheels or diamond-impregnated wheels, is used to shape gemstones to a desired rough form, called a preform . As with sawing, a coolant/lubricant (water or oil) is used to remove debris and prevent overheating. Very coarse diamond or silicon carbide, such as 60 grit, or mesh, (400 micron particles) or 100 grit (150 micron particles) is used for rapid removal of stone, and finer abrasive (600 grit - 30 micron, or 1200 grit - 15 micron) is used for final shaping and sanding. Back to techniques. Sanding Sanding is similar to grinding but uses finer abrasives. Its purpose is to remove deep scratches left by coarser abrasives during grinding. Since it removes material less rapidly, it also allows more delicate control over final shaping of the stone prior to polishing. For stones with rounded surfaces, a flexible surface such as a belt sander is often used to avoid creating flat areas and promote smooth curves. Back to techniques. Lapping Lapping is very similar to grinding and sanding, except that it is performed on one side of a rotating or vibrating flat disk known as a lap , and it is used especially to create flat surfaces on a stone (as in faceting). Laps are often made of cast iron, steel, or a copper-bronze alloy, but other materials can also be used. Back to techniques. Polishing After a gemstone is sawed and ground to the desired shape and sanded to remove rough marks left by coarser grits, it is usually polished to a mirror-like finish to aid light reflection from the surface of the stone (or refraction through the stone, in the case of transparent materials). Very fine grades of diamond (50,000 to 100,000 mesh) can be used to polish a wide variety of materials, but other polishing agents work well in many instances. Usually, these polishing agents are metal oxides such as aluminum oxide (alumina), cerium oxide, tin oxide, chromium oxide, ferric oxide (jeweler's rouge), or silicon dioxide (tripoli). Different stones are often very inconsistent in their ease of polishing, particularly in the case of faceted stones, so gemcutters are often very inventive in trying new combinations of polishing agents and polishing surfaces -- often tin, tin-lead, lead, leather, felt, pellon, wood, or lucite laps for flat surfaces such as facets. Rounded surfaces, such as on cabochons, are often polished on felt, leather, cork, cloth, or wood. Polishing removes small quantities of stone and can be used, especially when faceting small stones, to do ultrafine shaping of the stone. Back to techniques. Drilling When a gemcutter desires a hole in or through a gemstone (e.g., a bead), a small rotating rod or tube with a diamond tip, or a slurry of silicon carbide and coolant, is used to drill through the stone. Ultrasonic, or vibrating, drills are also very effective, but they tend to be costly and thus reserved for high-volume commercial drilling. Back to techniques. Tumbling Large quantities of roughly shaped stones are often tumbled, i.e., turned at a slow speed in a rotating barrel with abrasives and water for extended periods (days or weeks). By tumbling with progressively finer grades of abrasive (usually silicon carbide) and washing carefully between grades, the stones are gradually smoothed and polished to serendipitous but often very attractive shapes. Tumbling barrels are often hexagonal in outline in order to enhance the stirring action of barrel rotation. An alternative to rotatory tumblers is a vibratory machine, often called a vibratory tumbler, in which the containing barrel vibrates rather than rotates. The more stationary arrangement of vibratory machines makes it much easier to examine the progress of the stones inside, whereas standard tumblers must be halted in order to check progress. In addition to polishing gemstones, tumbling is often used to polish large quantities of metal jewelry. Back to techniques. Cabochons One of the simplest lapidary forms is the cabochon, a stone that is smoothly rounded and polished on top, relatively flattish, and either flat or slightly rounded on the bottom (which may be either polished or sanded). This form of cutting is often used for opaque or translucent stones, but is also frequently used for transparent materials that contain too many inclusions to yield a good faceted stone. Coloration and patterning provide the major interest in such stones. Cabochon cutting, or cabbing, is often performed by simply holding the stone in the fingers, but it is more commonly done by dopping (attaching with adhesive wax or glue) the stone to a wooden or metal dopstick. This facilitates twirling the stone to form smooth curves and avoid flat areas during grinding, sanding, and polishing. A typical cabbing machine holds several wheels representing a progressive series of diamond or silicon carbide grit, turned by a common arbor and motor, and a water supply that provides a coolant/lubricant to wash away debris and keep the stone from overheating as it is ground and sanded on progressively finer wheels. Back to forms. Faceted Stones Faceting is most often done on transparent stones. Flat facets are cut and polished over the entire surface of the stone, usually in a highly symmetrical pattern. The stone is dopped (usually with adhesive wax, epoxy, or cyanoacrylate glue) on a metal dopstick, which is then inserted in a handpiece that allows precise control of positioning. The cutting angle is adjusted vertically via a protractor and rotationally via an index gear . The facets are then ground, sanded, and polished on a rotating lap , while water or another liquid acts as a coolant and lubricant. When one side (top or bottom) of the stone is finished, a jig is used to transfer to the stone to a dopstick on the opposing side. A faceting machine usually employs a motor that turns a lap , a water supply, an adjustable handpiece with index gears and a protractor, and an adjustable mast or platform to hold the handpiece assembly. Most commercially available gemcutting machines employ a mast, but a few employ a platform. Two different styles of faceting machine -- mast-type (left) and handpiece and platform (right). In recent years, innovative faceters have employed techniques such as concave facets, grooves, and combinations of faceting and cabbing to produce new forms in faceted stones. Back to forms. Spheres are initially sawed into cubes or dodecahedrons and then ground to shape between two pipes or rotating concave cutters, allowing the stone to rotate freely in any direction to form a perfect spherical shape. As with other lapidary processes, gradually finer grades of abrasive are used to grind, sand, and polish the stone. While beads may be faceted, they are more commonly cut and polished as small spheres and then drilled to allow stringing. Bead mills are used to grind and sand large quantities of beads simultaneously. They typically employ a grooved lap and a flat lap between which the beads are rolled and worn to shape. After shaping and sanding, beads are usually polished by tumbling . Back to forms. Inlays In an inlay, a gemstone is cut to fit and glued into a hollow recess in another material (metal, wood, or other stones) and then the top ground and polished flush with the surrounding material. Stones most commonly used for inlay are strongly colored opaque stones such as black onyx, lapis lazuli, turquoise, tigereye, etc. Back to forms. Intarsias and Mosaics In both intarsia and mosaic work, small bits of different colored stones are fit together and the top cut and polished to present a picture or other interesting pattern. Strictly speaking, a mosaic is constructed on top of a flat base of another material (usually stone), while an intarsia (also known as Florentine mosaic, or pietre dure) is set flush into the surface of the base material. The finest intarsias and mosaics were traditionally of Italian origin, but intarsia has enjoyed something of a renaissance in recent years with the fine work of artists such as Jim Kaufmann and Nicolai Medvedev. Back to forms. Cameos and Intaglios Cameos and intaglios are similar in that both usually are carved portraits in stone or seashells. They differ in that cameos are raised portraits, while intaglios are carved down into the surface of the material. Both typically take advantage of different colored layers of material. The finest cameos and intaglios have traditionally come from Italy (usually shell) or Germany (usually agate). Back to forms. Sculpture Gemstones can be carved , like other materials, into almost any form, limited only by the talents of the sculptor. Carving is accomplished with a variety of diamond-impregnated steel bits , saws , and grindstones.