We have the expertise and engineering staff to design custom solutions for diamond grinding wheels and tools.
Cermet has been gaining popularity as a cutting tool all over the world. Its ability to withstand heat and its superior wear resistance make it a popular choice, especially for automotive applications. However, manufacturing cermet cutting tools is an altogether different experience. Here are a few tips to make grinding cermet cutting tools easier:
1.) Be patient. Cermet can not be ground at cutting rates that match carbide, or for that matter, even pure ceramic cutting tools. Cermets typically contain high levels of titanium as a binder and this material smears and loads diamond grinding wheels very rapidly. Cutting rates for cermets vary, but are commonly 50% to 75% that of carbide.
2.) Cermet collects rapidly on the surface of the diamond grinding wheel. Plan to dress the wheel frequently, as you are cleaning, not dressing away the Cermet.
3.) As with all materials, grinding wheel speeds will vary. Typical cutting speeds for cermets should be on the slower side, around 4500 SFPM.
4.) Coolant, coolant, coolant!! Always provide as much coolant and coolant pressure to the grinding zone as possible. Flushing the grinding zone with clean water soluble coolant will make the entire process of grinding cermet much easier.
5.) When all else fails, call Abrasive Technology, we have solutions.
Working together, Abrasive Technology and Aggressive Grinding Service developed a diamond grinding wheel that increased productivity by nearly 50%.
At Abrasive Technology, our product and application experts collaborate with you to optimize your process and determine the best solutions for your specific goals.
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.
A reoccurring challenge I confront when visiting customers using superabrasive OD (outer diameter) grinding wheels is variations in performance among wheels. They want a consistent, sustainable (both in price and wheel life) wheel that grinds the same every time.
To produce an OD grinding wheel with a width of greater than 2”, individual 1” wheels are made and then glued together to form the desired width (with a goal of producing identical 1″ pieces for consistency).
However, consistency can prove challenging. Assuming that the bond and superabrasive are properly prepared, the manufacturing process will likely include variations in:
- Mold setup when multiple molds are used
- Hot press equipment used
- Uniformity of pressure around the molded band
- Temperature ramp up & consistency
- Procedure of loading the molds
- Procedure of pressing the mold
- Bond density when compacting the loose powder matrix
Add the facts that different operators run machines at different times and there’s limited QC domumentation of the pressing cycle from wheel to wheel, it is easy to see that achieving absolute consistency in each 1″ piece is difficult. And when multiple wheels are then glued together to make one large wheel, it’s no wonder machinists can encounter variations in wheel performance.
In order to solve these inconsistencies, I suggest using a solution that:
- Is computer-controlled
- Develops one uniform wheel rather than several individual wheels pressed together
- Creates uniform density from OD to ID and from side-to-side
- Relies on QC process documentation, which shows the precise process for each individual wheel.
- A whole-system approach to ensuring consistency is your best bet when OD grinding. By using a solution that follows these guidelines, you can be assured that each wheel is the same as the one that you ordered last time.
Abrasive Technology’s patented VFLex® OD Grinding Wheel is made with a computer-controlled process to achieve uniform density throughout the entire abrasive section. Learn about the VFlex® process by selecting Centerless Grinding Wheel Flyer.
If you have a question about a grinding or tooling challenge, please don’t hesitate to Ask an Engineer now!
An entrance washed in color. Banners flying in the air. Diamonds as far as the eye could see.
A crowd gathered. There were big winners. And others who left with only what they brought with them.
The Summer Olympics you ask? No, it was the “We Champion Superabrasives” event at Abrasive Technology’s Lewis Center headquarters.
The event, attended by AT associates, highlighted products and processes from AT facilities across the globe for the aerospace, medical, general industrial, oil & gas, and stone markets. AT Sales and Business Development associates served as hosts at each expo station, helping to make a connection between the tools the company produces and the resulting end products.
Associates mixed and mingled throughout the event, learning more about the extensive AT product line and enjoying prizes, a photo booth and refreshments.
Golden memories for all.
Grinding a combination of carbide and steel can be a particularly difficult problem when using superabrasives. The main question is: Should Diamond or CBN be used to grind this combination of materials?
Punch dies used specifically in the plastics and printed circuit board industries and known as “lamination dies” are most commonly made of both materials. The cost of making very large lamination dies would be prohibitive, if made completely of carbide and would wear very quickly if made just from tool steels. Therefore, the most common practice is to make the punches and the areas around the holes being punched in carbide for maximum wear resistance, while the rest of the die plate is made of various tool steels.
Now, back to the original question; should diamond or cbn be used to grind a combination of carbide and steel? The answer is actually simple: CBN can’t and will not ever grind carbide. Whereas, diamond can grind steel and easily grinds the carbide.
Of particular importance, Abrasive Technology provides a very effective wheel specification for this application utilizing “XD” type diamond which is a tougher, blockier, and stronger type of diamond. When this diamond is bonded with our B170 resin bond and used in wet grinding applications our product is an excellent choice for customers to use.
Have a question about grinding carbide and steel? Ask an Engineer Now!