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Sharpening carbide and grinder selection

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Contributed by Forrest Addy

I feel comfortable in making a catagorical statement: There's only one
abrasive for finish grinding carbide tooling and that is diamond. All
non-diamond grinding wheels and combinations do a second rate job.

Different materials require different abrasives for grinding or sharpening.
Silicon (not silocone, by the way - that's the family of silicon based
plastics) carbide isn't much harder than carbide. The green silicon carbide
wheels are made very soft and work best to rough grind tungsten carbide prior
to finish grinding with diamond and to clearance the steel shank away from
the carbide in the case of brazed on tooling.

Borazon (Norbide and other trade names) is boron carbide. It's a
"superabrasive" like diamond, but it's unsuitable for grinding carbide.
Borazon is specifically designed for grinding hardened high speed steel such
as milling cutters. Borazon wears rapidly if used to grind soft steel.
Comparable borazon and diamond wheels are about the same price.

Diamond is unsuitable for grinding steel and in fact rapidly wears away in
contact at grinding speeds with steel of any kind. Silicon carbide generates
too much heat for finish grinding carbide tooling. It micro fractures and
flakes the fine corners. Very careful dressing and and inspired touch may
result in good free hand ground carbide tools. The problem is, you know what
happens to the work if an Acme threading tool flakes in the cut: disaster.

If you wish to grind carbide and do it well, you have make the investment in
a diamond grinding wheel. The best off hand carbide grinding package I've
found is Enco's import copy of the Balder #500 6" face bench grinder with a
220 grit diamond face wheel on one end and a green silicon carbide wheel on
the other. Total package price is $350 depending on the quality of the
diamond wheel. Remember, these grinders grind on the side face of the wheel,
not the periphery. This allows close control of clearance angles by setting
of the work tables and supplied miter gages. Be sure you get the plate
mounted wheels this grinder requires.

The $220 6" Enco face wheel grinder is not reversible, but the Baldor #500 is
for $620. It's easy to make the Enco grinder reversible if one were to open
it up and separate both ends of the start winding from the run winding so it
turns into a four lead motor and providing a suitable center off switch. I
have two of these Enco grinders made reversible: one for HSS lathe tools and
one for carbide tools and machine scrapers.
 








 
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