We have the expertise and engineering staff to design custom solutions for diamond grinding wheels and tools.
Our patented VFlex® technology consistently produces uniform resin bond diamond and cBN wheels up to 12″ wide in one piece (and sizes up to 24″ in diameter). The computer-controlled compression molding system produces a consistent, identical wheel each time one is made. The VFlex® process also increases wheel density and virtually eliminates deviation in hardness throughout the entire abrasive section for predictable wheel performance.
Diamond handpads come in a variety of shapes, but the rectangular 2 1/4” x 4” format is by far the most popular version since it fits so easily in the palm of the hand. The handpad consists of a diamond section (small islands of diamonds on a flexible layer that permit a certain amount of flexibility) glued onto a foam support. The diamond islands are available in two basic forms:
- Electroplated: grits range from coarse grit sizes such as #30 to fine sizes such as #1200. The most popular grit sizes for marble being #70, #220, and #400.
- Resin bond: grit ranging in size from #600 through #3500.
Resin bond products have no scratching ability of their own other than the diamond itself. The resin base only holds the diamonds in place, making them ideal for polishing applications. The diamonds produce successively finer scratch patterns until the patterns become so small that to the human eye, the surface appears polished. As every fabricator knows, nothing is more frustrating than to finish a job and then notice scratches still present on the surface. Resin bonds are generally less “aggressive” than electroplated metal bonds. They are more forgiving and therefore do not leave large, undesirable scratches.
For a typical job that calls for polishing a rough cut granite edge, try this procedure: in succession, use the electroplated #70, #120, #220, and #400 grits followed by the resin bond #600, #800, #1800, and #3500 sizes. This sequence will produce a glossy finish on almost any stone. Note that when working with marble or granite, an additional buffing sequence will bring out the full gloss of the stone.
For special applications, very fine grit diamond hand pads (8000 and smaller) or very coarse grit pads are available. For grits finer than #400, the most economical encapsulation method is resin bond because, as I mentioned above, they’re more forgiving than electroplated metal bond.
Important Considerations for Custom Handpads
Manufacturers can deliver a custom solution for every stone-cutting preference and need. When diamond handpads are tailored for each aspect of a job, manufacturers pay close attention to these important considerations:
- Rigidity – important to maintain a flat, mirror like surface on products such as counter or table tops. Hand pads used for these surfaces are generally made with foam handles and offer the best characteristics of an all-around tool.
- Flexibility – key to those who polish rounded surfaces such as bullnoses or ogee shapes. Diamond handpad material is available from manufacturers and can be cut into strips of any size. These strips can be fastened with hook-and-loop backing to specially shaped forms which mirror the shape of the finished edge.
- Ruggedness – essential for heavy-material removal, such as tile edging and sizing, or even rough work on hard stones. Although still foam-mounted, custom handpads can be made on very rigid substrates with much larger diamond islands, allowing them to withstand the greater pressure.
Water is Essential to Diamond Hand Pads
For a better finish and to extend the life of the handpad, be sure to use water while polishing. Although some work can be done dry, water offers important benefits. For example, because resin bond diamond handpads are particularly intolerant of heat, water is an essential accompaniment. The water not only rinses away the cuttings (dirty water) from the stone’s surface, it also cools the diamonds and prevents the resin base from overheating.
The Power of Orbital Pads
Any time hand pads are the best tool for the job, orbital pads are the only power alternative to consider. Orbital pads are mechanically powered, and therefore offer relief from excessive arm muscle fatigue. The power tool to which they are attached should have a “jitterbug” or vibratory type of motion. This is important because if more work is done with one grit versus another (because the arm gets tired), the finished stone will not display an even degree of reflectivity and could translate to poor workmanship. Orbital pads are larger than hand pads and are available in the same grit sizes. They are also available in a wide variety of dimensions to match the power tools being used.
Don’t Work Too Hard
There’s no question a shop can experience solid benefits from the proper use of diamond hand pads. The fabricator should be able to profit by:
- Saving time
- Achieving consistent finishes
- Increasing productivity
- Reducing costs
The single most important thing to remember when using diamond hand pads – let the diamonds do the work. In other words, don’t treat a diamond hand pad like one made of silicon carbide. Forcing the hand pad to work harder than necessary will only decrease its useful life.
The use of superabrasive (diamond and cubic boron nitride/cBN) wheels
to perform centerless grinding has existed for nearly 50 years – it’s a
relatively simple process of following the directions of the machine tool manufacturer and the wheel manufacturer. However, having spent some
35 years in this industry, I have all too often seen an operator relying heavily on the wheel to solve challenges associated with the grinding process. Operators should also pay special attention to machine set-up since proper set-up can help cure many of the most common grinding issues.
Below you’ll find some fundamental set-up procedures for the average centerless grinding machine. I will cover the topics broadly – if a more detailed answer is required, please leave a comment in the section below.
Trueing the Regulating Wheel: The function of the standard regulating wheel trueing unit is to make the diamond trueing nib follow the same line of contact with the wheel as that of the work.
Factors to consider:
1.) Angle of inclination of the regulating wheel.
2.) Location of the center of the work in relation to the regulating wheel and the diamond wheel.
3.) Angle to which the regulating wheel is swiveled.
4.) Amount the diamond nib is “set over.”
5.) Using the highest wheel RPM of the regulating wheel during trueing to create a smooth, consistent feed surface.
Work Blades: When grinding with diamond or cBN wheels, the most common work rest blades are made of steel with a carbide blade insert attached. PCD work rest blades are also available, but are quite expensive when compared to carbide. Under most normal grinding circumstances, the centerline of the work piece should be located above the centerline of the grinding and regulating wheels. If the centerline is set too high, the work piece may exhibit chatter, and if set too low, the work piece may exhibit an out of round condition with three high lobes.
Choosing the correct work rest blade angle is also important to the set-up process. For example, when grinding with a 4” wide superabrasive wheel, the work rest blade should work well at 30 degrees. However, once the width of the wheel is changed to 6” or 8” wide, the 30 degree work rest angle may generate too much pressure and cause unwanted chatter. Changing the work rest blade angle to 20 or 25 degrees will reduce the pressure toward the grinding wheel and eliminate the chatter on the part.
When regrinding work rest blades, it is important to not burn the blade. For high speed steel, aluminum oxide wheels will be effective if infeed rates do not exceed .0005” per pass. If a very high quality tolerance is required on the work rest blade, a cBN wheel should be used. When re-sharpening carbide work rest blades, a medium hardness 120 grit diamond wheel should be used. Performing light passes between .0005”- .001” with spark out passes in between is recommended to ensure maximum flatness of the blade.
Coolant & Coolant Flow: A common misconception I encounter deals with coolant flow and the direction of coolant. Many people believe coolant is used solely to keep the grinding wheel cool. Underestimating the importance of the placement of the coolant at the interface between the grinding wheel and work piece can be a critical mistake. Coolant removes heat from the grinding zone where the workpiece actually makes contact with the grinding wheel. A failure in alignment of the coolant will cause grinding heat to return to the work piece and/or the grinding wheel. Once heat enters the work piece, the operators’ ability to hold tolerances for roundness and straightness becomes substantially more difficult. In extreme heat situations, the diamond wheel can be damaged thermally, exhibiting blisters and cracks.
During the grinding process, the air barrier created by the grinding wheel and work piece must be overcome to allow coolant to interface between the two. Properly pressurized coolant will remove heat from the grinding zone, allowing a free cutting grind process and ensuring optimum performance capability. Using coolant nozzles that enhance the flow of coolant pressure will further help to increase wheel life and facilitate the free cutting nature of the diamond wheel.
I also see more coolant scrubbing systems being added to the back side of the wheel. This practice utilizes a high pressure nozzle system (with pressures exceeding 600 PSI) to “scrub” the diamond wheel removing material, or “swarf,” that has been ground from the surface of the grinding wheel. Customers often believe a wheel loaded with swarf creates a better surface finish on the work piece. However, performance of the grinding can be reduced by 50% from a clogged grinding wheel. Additionally, increased pressure generated during grinding with a clogged grinding wheel can reduce overall wheel life by 20-30%.
Trueing a Superabrasive Wheel – Trueing a superabrasive wheel on a centerless grinder can be a time consuming process. Here are a few tips to make the truing process easier:
1.) Never use diamond nibs when trueing a superabrasive wheel. Nibs will generate flats on the tips of the abrasive and may generate too much heat, potentially damaging the bonding agents.
2.) The superabrasive wheel should be mounted on the machine’s wheel adaptor, which adapts the wheel to fit. Always balance the wheel assembly before operating in the grinding mode. Balancing the wheel/adaptor assembly prevents premature wheel breakdown and the potential risk of a wheel explosion during the grinding process.
3.) Most commonly, soft carbon steel rod can be used to safely true the wheel, removing run-out from the outside diameter of the wheel. Alternating the use of the steel rods and a good sized cleaning stick (dressing stick) will help speed up the process of trueing. A properly trued and conditioned centerless diamond wheel is critical to attain optimum wheel performance.
4.) Once the diamond wheel appears to have obtained total concentricity to its bore, use a grease pen, crayon or china marker and draw lines on the outside diameter of the wheel. Re-run a few steel rods – taking light passes of .0002” to .0005” – if the wheel is true the lines on the wheel will disappear. Use at least one cleaning stick to condition the wheel, exposing the superabrasive crystals to grind the material efficiently. Depending on the size of the wheel it can take several cleaning sticks to achieve proper grinding efficiency.
Once the wheel has been completely trued and dressed, it is important to verify that the entire surface of the diamond wheel is in use. Setting the angle of the regulating wheel too acutely will cause the work piece to enter too far into the grinding zone and cause uneven wear and, most important, taper. This will lead to reduced wheel life. Setting the regulating wheel angle too close to parallel with the diamond wheel will cause stalling of the parts between the regulating wheel and diamond wheel. In extreme cases it can cause a work piece/wheel crash at the entry side of the diamond wheel.
Abrasive Technology is a leading manufacturer of diamond grinding wheels and tools, including the revolutionary VFlex® resin bond centerless wheels. Learn more about Abrasive Technology or, if you have a specific need, please Ask an Engineer .
Here’s a quick view of how Abrasive Technology internally shared the global team’s experience, ingenuity and craftsmanship in its work with diamond and cBN grinding wheels and tools.
The company hosted a We Champion Superabrasives Expo at its Lewis Center Headquarters and showcased electroplated, resin, and P.B.S.® braze bond tools manufactured in facilities around the globe.
Abrasive Technology is a global leader in superabrasive tooling, working in markets including aerospace, oil & gas, dental, medical, general industrial, composites, electronics, stone and more. To learn how AT can solve your toughest tooling challenges, visit our website.
Grinding shops commonly treat ceramic grinding in the same fashion as hardened steels or carbide. Understanding the differences can save a great deal of grief (and scrap too).
1.) Generally speaking, ceramics are not heat conducting materials. Maximize the removal of heat from the grinding zone by using an ample supply of water based coolant.
2.) Use a diamond wheel that has been designed to grind ceramics. A tougher and stronger diamond crystal is typically required to stand up to the hardness of ceramics.
3.) Make sure the wheel has been sufficiently cleaned and trued before grinding ceramics, especially if the machine has been used to grind other materials.
4.) Make sure you understand the specific type of ceramic you are grinding. Alumina based ceramics are generally very easy to grind. However, it is not uncommon for alumina to be mixed with various metals (like titanium or nickel) or even a wide variety of other types of
ceramic material (such as zirconia).
5.) Start grinding by using very conservative in-feeds to develop a feeling for how the machine handles the grinding load and to avoid generating
too much heat on the part.
Almost all diamond disks in use today for polishing stone consist of diamonds embedded in a resin (plastic) matrix. Diamonds are mixed with the resin to form blocks rather like the lug pattern on the soles of shoes. The diamonds are randomly scattered throughout the resin matrix to a specified depth. As the resin matrix is worn away, the diamonds are gradually exposed.
A wide variety of diamond disks is available today. Popular sizes for the fabrication shop are 3″, 4″, and 5″ diameters, where 4” is by far the most popular and larger and smaller sizes are typically reserved for specialty uses.
The most popular grit sizes for electroplated disks are #70, #120, #220, and #400. Beyond that, there is ample demand for both the coarser #30 and #50 grits and well as the much finer #600, especially for marble work.
Grit sizes for resin bonded disks commonly range from the coarsest #30 to a very fine #8000. Typically, #50, #120, #220, #400, #800, #1800, and #3000 are most commonly used in the shop for processing granite surfaces. Marble processing is less stringent and the combination of grits #50, #220, and #800 usually yields the desired finish.
A point has to be made on the abrasiveness of the stone itself. Marble is soft, but tends to yield a more abrasive slurry than granite, which is harder but less abrasive in slurry form. Some shops try to polish both types of stone with a single set of disks, and this is a mistake. Disks are recommended for specific materials based on grit size, plus the bond (electroplate, metal, or resin), the number of diamonds that are working at any given time, and the hardness and abrasiveness of the material. Some disks work well with marble and poorly with granite, just as a marble diamond saw works well on marble and inadequately on granite. There are no universal disks any more than there are universal saws.
Flexibility vs. Rigidity
There is a trade-off between the flexibility and the rigidity of diamond polishing disks. Flexibility is usually achieved with the use of a rubber universal joint mounted on the spindle of a right-angle grinder, or by using a flexible disk attached with a hook and-loop fastener. Rigidity is the result of a rigid disk attached with a snail-lock fastener. A good compromise consists of a rigid disk and a hook-and-loop fastener.
Flexible disks tend to conform to the surface of the material, polishing high and low areas with equal ease. In heavily veined marble or on extensive granite surfaces, the flexible disk will tend to ride over the hard areas and dig into the softer portions. The job may go quickly, but the finish will be wavy. Moreover, the flexible disk will not do a good job of levelling untrue surfaces.
Rigid disks, on the other hand, will do a better job of levelling and have less tendency to dig into soft areas. The rigid disks are also less forgiving; the slightest inconsistency in the polishing procedure will show up as a flaw when the work is completed. The novice can usually obtain better results with a flexible disk. The experienced craftsman will generally prefer the rigid setup. Rigidity prevents rounding of the edges and produces a flatter desirable surface. In all cases, a slight cushioning is necessary to prevent rapid wear of the diamonds due to vibrations generated during the rapidly rotating polishing sequence.
Water is a desirable component of diamond polishing, since it efficiently cools both the work and the disk. (Resin bonds especially are quite intolerant of heat build-up.) Beyond its cooling properties, water flowing over the work at a steady rate yields other advantages: the job will go faster with less effort because the slurry helps remove material, there won’t be any dust, and the finished surface will be superior to anything that can be done dry. This is just as true for hand-held grinders as it is for large production machines.
For diamond abrasives, the best speeds are typically 3000-7000 RPM for a 4″ disk. Higher speeds allow the diamonds to do the work rather than relying on pressure. In fact, excessive pressure will noticeably shorten the life of a diamond disk.
All resin-bonded disks need to be broken-in, a process that exposes the diamonds enclosed in the plastic matrix on the surface of the disks. This is easily done for all grit sizes on the rough surface of the material being worked. With the coarse grits, simply attach the disk and start grinding. For the finer grits, e.g., #3000, break-in is best done on a surface that would be produced by a coarse grit of #120 or so.
A #3500 disk can be broken-in during the normal polishing routine, i.e., on a surface produced by a #1800 disk, but it will take some time. A disk is broken-in when all the grinding surfaces have lost the gloss they had when they came out of the package.
On the basis of materials only, diamond polishing tools are significantly more expensive than silicon carbide tools. The overall advantages, however, clearly favor diamonds: less grinding time, improved production rates, better finished surfaces, and longer disk life. These important benefits lead to improved profitability.
For disk polishing with hand-held grinders, the advantages of diamonds include:
• A 50% reduction in polishing time.
• A cleaner shop without the dry grinding dust.
• Reduced worker fatigue with lighter tools requiring less pressure.
• Increased production throughput.
For more information about grinding and/or polishing stone, visit our website or feel free to 080 about your specific needs.
As we were testing (playing with) the Jack of ALL Blades™, we naturally began to wonder about the potential uses for this kind of diamond grinding wheel. Two specific factors helped to drive the idea of using this blade for rescue work:
- My brother is a local fireman who is involved with the rescue unit in central Ohio
- The earthquake that devastated Haiti occurred while we were developing this blade and we couldn’t help but think it could be useful for rescue teams to be able to quickly cut through rubble made of a variety of construction materials including concrete, rebar, other metals, wood, etc.
In an effort to test this blade for rescue conditions, I made a few molds and used them to make concrete blocks with rebar running through them. I contacted my brother to see if we could go to the junkyard with the local firemen while they were training and cut on cars & school buses… yeah it was fun!
Through this “real world” rescue & construction type testing we learned a few things:
- this type of blade can dry cut concrete very rapidly, and it lasts quite awhile cutting only concrete.
- it cuts automotive glass very effectively with almost no wear on the blade. We also learned that it will cut steel pretty well, but it dramatically reduced the life of the blade compared to just concrete and other common construction materials.
- as the blade wears from metal cutting, it degrades the cutting ability of the blade on softer materials like wood.
These lessons led us to another natural progression… how can we make the Jack of All Blades™ cut metal effectively without killing the overall life/effectiveness of the blade for other materials?
Next up, development of a metal (specifically steel) cutting saw blade using man-made diamond superabrasives. Check back in a week or subscribe to our blog in the box to your right.
If you or someone you love is a First Responder and you think this solution could help, Ask an Engineer about details regarding the mixed-material cutting solution: Jack of All Blades Now!