Dear MikeHalloran:
Excellent question.
C2 - HC25
C4 – KCr06
Here are the properties the two grades of carbide are supposed to have. However they were sold under the C-2 and C-4 designations which means that the supplier has deemed them suitable for use as C-2 General Purpose and C-4 Precision work in cast iron, non-ferrous and non-metallic materials.
HC25
K20 ISO, C2 ANSI, 7 % Co, 93 % WC, 14.9 Density, 1530 HV30, 91.5 HRA 2600 TRS (Mpa), 377,000 TRS (PSI), 1.3 - 2.5 Grain
KCR06
3% Co, 97 % WC, 15.25 Density, 1910 HV30, 93.6 HRA, 2300 TRS (Mpa), 334,000 TRS (PSI), 0.8 - 1.3 Grain
(Note: I was once given these values but they appear to be no longer available.)
The carbide companies that sold as these parts used to have a truly excellent operation in South Carolina. Then they hired a new company president who was living in Pennsylvania. The new company president bought a company in Pennsylvania and moved the South Carolina company to Pennsylvania.
The employees in South Carolina were extremely unhappy to be losing their jobs and none of them transferred to Pennsylvania.
In the two years or so they were in Pennsylvania we never saw the kind of quality they produced in South Carolina.
A year or so ago they move the entire production operation to Michigan and, again, none of the plant people went with them.
Again, the people in Pennsylvania were extremely unhappy to be losing their jobs.
Up till about six months ago we were being offered tens of millions of assorted carbide saw tips in different sizes and grades at a pretty good discount. We were assured that most of these tips would work pretty well.
The C-2 tips showed a huge amount of breakage. This should not happen before with C-2 tips from the same supplier to the same manufacturer for the same end-user.
Conclusion:
Under the C system, the C-2 were good tips because the manufacturer said they were and that is the way that system works. Personally I think that material should be sold either by objective standards for a suitable for the intended use.
Also, I am incredibly biased in this instance, because I sold a batch of carbide to a very good customer who had horrible results.
Thomas J. Walz
Carbide Processors, Inc.
Good engineering starts with a Grainger Catalog.