From the book Building Superior Brazed Tools  Buy the Book

 There is no comprehensive comparison of tungsten carbide between and among tungsten carbide suppliers.  A big part of the problem is the huge number of suppliers, grades and trade names.   There are at least 5,000 different grades of tungsten carbide sold under more than 1,500 different trade names by more than 1,500 different companies.  Refer to our Carbide and Advanced Material Index for more information on Carbide Material. 

There is no true standard.  The US "C" designation, The ISO designation and other designations are not necessarily relevant.  Tungsten carbide from two different manufacturers may have identical designation but vary widely in almost every imaginable way including performance.   

C grades

The original concept was to rate tungsten carbides according to the job that they had to do.  If you had a particular job you would specify a "C" grade of tungsten carbide and you could buy from anybody.  This has lead to a situation where a C-7 tungsten carbide can be almost anything as long as it does C-7 style work.   According to Machinery's Handbook it can range from 0 - 75% tungsten carbide, 8 to 80% titanium tungsten carbide, 0 - 10% Cobalt and 0 - 15% Nickel.   The problem is that two C-7 tips from two manufacturers will almost certainly work very differently in two different applications.  

A common misconception is that there is a straight progression from C-1 to C-14 or wherever.  A common view is that each higher grade has less cobalt in the binder and is therefore harder and more likely to break.  Following this line of thought is belief that the higher C number is harder and better for wear resistance.  This is like classifying automobiles by size from a moped to an eighteen-wheel semi.  This is clear and handy but unfortunately it is not true.  

C grades classification

C-1 to C-4 are general grades for cast iron, non-ferrous and non-metallic materials

C-1       Roughing                      

C-2       General Purpose

C-3       Finishing

C-4       Precision

Steel and steel alloys - these grades resist pitting and deformation

C-5       Roughing                      

C-6       General Purpose

C-7       Finishing

C-8       Precision

Wear Surface

C-9       No shock

C-10     Light shock

C-11     Heavy shock

Impact

C-12     Light

C-13     Medium

C-14     heavy

Miscellaneous

C-15     Light cut, hot flash weld removal

C-15A  Heavy cut, hot flash weld removal

C-16     Rock bits

C-17     Cold header dies

C-18     Wear at elevated temperatures and/or resistance to chemical reactions

C-19     Radioactive shielding, counter balances and kinetic applications 

Every task using tungsten carbide is different.  Northern sawmills know that the cutting varies with the temperature.   Identical knotty pine cuts differently frozen in December than it does warm in July.  Boeing machinists can often tell the difference in different lots of Aluminum that are supposedly identical.  Each and every cutting job needs a different set of factors to be successful.