Dick wrote:

I've got a H/F lathe tool grinder, a copy of a Balder or something. Any
way I have read that the green wheels are for carbide but that you shouldn't
sharpen tool steel on a green wheel. I'm thinking about getting a diamond
wheel to put on this and was wondering if tool steel can be sharpened on the
diamond wheel? Also, which diamond wheel would you get if you could only get
one, coarse, medium or fine? As always, thanks in advance for your comments.
This is by far my favorite forum.
Dick

Most diamond wheels should NOT be used on regular (high speed) grinders
to grind steels. They are fine for carbide. The same is true for the
'green' Si-Carbide wheels. Grinding steels will soon wreck either type
wheel. Note: ... there are LOW speed diamond wheel grinders that can be
used on steels (Glendo, etc.) ... these are a whole different animal
than the so called 'carbide' grinder you purchased.

For common tool steels you should get a 'white' aluminum oxide wheel.
These are available with the steel backs as required for this type
grinder. MSC has them, as do others.

One thing to watch out for. I bought two of the HF grinders, one for my
home shop, one for university where I work. They are generally
satisfactory, BUT ...

One cast-iron wheel guard on one grinder was bored a bit off center. No
problem with the 'green' wheels provided. I ordered two 'white' wheels
from MSC, and these were about 1/8" larger in diameter. That was perhaps
1/16" too big to fit in the off-center wheel guard.

I solved the problem by unbolting the bad wheel guard and setting it up
on the rotary table on my mill, then milled out the inside of the guard
to approximate concentricity with the mounting hole. Only a small amount
needed to be removed from one side of the guard ... ample thickness
remained. I used a ball-end mill to avoid any sharp stress-riser
internal corners. Now it works fine. This was a minor job for anyone
with a mill. I suppose it could have been done freehand with a die
grinder and some care.

Considering that the HF grinder is about half the cost of the other such
imported grinders, it seems a good value, even WITH the added work on
one of four wheel guards. It's a just typical HF (and imported in
general) quality control problem.

Dan Mitchell
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