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Proper Care & Setting Instructions


SP3 Ultra-Mill Proper Care & Setting Instructions (Inch Cutters)

SP3 Ultra-Mill Proper Care & Setting Instructions (Metric Cutters)

 

General Questions


What is diamond? Diamond is composed of pure carbon atoms, arranged in a very special crystal orientation that gives it its unique physical properties. The key element that allows for the special crystal structure is the “sp3” bonding of the carbon atoms—and that is where sp3’s company name comes from. Diamond is the hardest and most abrasion-resistant material found in nature. It is chemically inert with most materials, it is the best thermal conductor in nature and it is electrically non-conductive. Diamonds can be created using heat and pressure (as in nature) or heat and vacuum. The CVD process uses heat and vacuum to grow diamond crystals and is a cost effective way of creating diamond.

What materials are best suited to machining with diamond? Abrasive non-metallic materials, non-ferrous metals, and abrasive non-ferrous metals.

Why can’t you machine ferrous metals with diamond? Diamond is unaffected by almost every other chemical or compound in nature. One exception is hot iron. The carbon atoms in diamond will dissolve into the iron, quickly eroding the diamond surface. Iron wheels are used for polishing natural diamond. That said, under certain conditions and with certain cooling substances, it is possible and even desirable to machine ferrous materials using diamond. Contact sp3 for details.

How thick is the diamond on sp3 tools? Thickness is tailored to the application, and can range from 5 to 50 microns.

How do coating thicknesses in microns relate to inches? 1 micron is 1 millionth of a meter, or 0.00004 inch. A coating thickness of 10 microns is therefore 0.0004 inch; 40 microns is 0.0016 inch.

How do you grow diamond? The diamond coating is grown in a vacuum chamber using feed gases of hydrogen and methane. Usually the gases are fed into the chamber in a 50:1 mix, predominantly hydrogen. A very high temperature element in the chamber causes the deposition process to take place.sp3 uses fine filaments energized to a temperature of approximately 2200°C. The high temperature breaks down the methane into carbon and hydrogen. The carbon atoms will nucleate and grow tiny crystals of diamond. In time these tiny diamond crystallites will grow into a continuous diamond film.

How long does it take to coat a tool? Diamond grows slowly, about 0.5 to 1.0 micron per hour. A typical reactor run to grow 40-micron films on inserts can take almost two days; most round tools are coated overnight.Because of the slow diamond growth rate sp3 finds ways to maximize the number of tools that are coated in every reactor run.

How many tools can be coated in a reactor? The sp3 reactor provides a uniform diamond coating over an area of about a square foot. This enables coating 200 to 300 inserts at a time, or 65 to 100 round tools.

Why are diamond-coated tools so expensive? Primarily because of the slow growth rate of the diamond film—0.5 to 1.0 micron per hour. Another factor is pretreatment of the substrate to guarantee good adhesion. As pretreatment and deposition processes are further developed costs will drop, as they do in most maturing technologies.

How do you make the diamond coating stick? Left to itself, diamond has almost no chemical bond to cemented carbides. The trick is to pretreat the carbide surface, roughening it so the diamond can grow into the surface and attach itself through the mechanical interlocking of the carbide and the diamond.

How sharp is the cutting edge on a diamond-coated tool? The coating will naturally tend to round the edge somewhat. Sharpness is a function of the sharpness of the uncoated tool and the thickness of the film. Thin (10 micron) films over a dead sharp edge are still quite sharp. Thicker films, e.g., 40 microns, will approach an “A” hone in sharpness.

Custom Coating


What carbide grades can be coated? This can’t be answered in just a few words. In general, typical C2 nonmicrograin carbides are the best candidates. For a complete list please contact Customer Service at 888-547-4156.

Can sp3 coat micrograin carbides? sp3 can coat down to about a 1 micron carbide grain size. If the carbide is too fine it does not respond to the preparation, which requires a rough surface for good adhesion.

If I send sp3 a tool, can they coat it? If it is in an approved carbide grade and the geometry within our limits we an coat it.  Please contact Customer Service at 888-547-4156 with specific questions.

If I send sp3 a tool in an acceptable grade for coating, how long will it take? sp3 can typically turn around custom coating requests in about 10 working days.

Can tools coated with other coatings such as TiC and TiN be coated with diamond? Unfortunately not. sp3 needs a bare carbide tool of the proper grade to insure a successful bond between the diamond and the carbide.

Can tools be diamond coated a second time? sp3does not coat tools that have already had a diamond coating for two reasons. The first is that the diamond deposition process alters the carbide at the surface, and the required surface preparation will be less predictable a second time.The second reason is the uncertainty of the integrity of the ground edges. Often a tool is run until the diamond film is worn through in one or more spots. The carbide substrate will wear very quickly once the diamond is gone, leaving a notch or groove in one or more spots on the tool. These defects are difficult or impossible to remove with further grinding.

Can HSS tools be coated? During deposition the substrate temperature is about 850°C. High-speed steel will not survive these high temperatures.

Can tools with brazed carbide tips be coated? The normal deposition temperature is 850°C. Typical brazing will not survive these high temperatures.

Can you braze diamond-coated tools? This is feasible if the braze is done in a non-oxidizing atmosphere such as argon, and temperatures are kept as low as possible. However, one consideration is that the tool cannot be touched up or ground to size after brazing. You would be grinding a thin diamond film, and it would be very difficult to grind accurately without the possibility of breaking through the film.

Machining with diamond tools


Can I expect longer tool life than carbide with diamond and, if so, how much longer? Yes, you can. How much longer depends a great deal on the application. In very abrasive metals such as 390 aluminum a 10x life increase in not uncommon. In graphite, lifetime increases between 30x and 50x are common. In glass fiber filled materials 30x is common.

What are the advantages of diamond other than longer life? Accuracy: The diamond coating is very thin, but very hard, and tools don’t change significantly in size during their life. For instance, the radius on an endmill will change by about 10 microns (0.0004″) from when new to the point that it is worn out.
Speed: Diamond tools can typically be run at two to three times the surface speed of carbide tools.
Dry cutting: Diamond tools can often convert an operation from wet to dry machining, providing a significant saving in overall machining costs.

Should you use coolant with diamond tools? Diamond tools can often be run dry. In some cases coolant can shorten tool life due to thermal shock.If coolant is used for chip removal, it can provide a better finish in some applications. Coolant also contributes some lubricity which can be helpful in some applications.In general, we recommend to try running dry or with mist coolant. Use flood coolant only when chip removal or finish demands it.

How do diamond-coated tools perform with respect to surface finish? The application of a diamond film to a tool has the effect of making the tool less sharp. What is the consequent effect on surface finish?First, the question must be asked—what do we mean by finish? Is it an Ra reading using a profilometer, or is it surface sheen or brilliance that is important?In terms of an Ra reading, CVD diamond tools often provide a finish similar to carbide or PCD tools.With respect to visual finish, diamond films are composed of millions of tiny crystals, which will cause micro scratches on the surface of some materials, leaving a matte finish rather than a mirror finish. If a particular finish is required, we usually suggest PCD or TFd tools. This is one of the reasons sp3 provides all three kinds of diamond tools. We work to match the tool to the task required.

What is the difference between DLC and diamond coatings? DLC is an amorphous carbon film called Diamond Like Carbon. It is not diamond because it is not crystalline. DLC films are typically 1 to 2 microns thick, and do not hold up in very abrasive materials such as silicon aluminum. In graphite they will typically last about 10 to 15% of the life of a diamond tool.