In article , B.B.
says...

While I'm thinking of it...
As I understand things, if I do change the height of the cutting edge
the only real drawback is that I need to compensate and move the tool up
until it's level with the centerline. Correct? The lathe I've been
using has a quick-change post that lets me set the height, and I have a
feeler gauge set that's unreadable now, but would make dandy shims if
I'm ever using a non-adjustable tool holder.

As harold said, basically "yes." If you have an aloris or other
import QC toolholder you don't have to worry about shims. Eventually
you will wind up with a non-adjustable one and have to worry about
it. Just face off a piece of stock in the spindle, and that will
tell you if you are are high or low. If low it will leave a pip
there, if high the tool simply won't cut well when you get down
to the center. You should understand the relationship between
center height, front clearance, and rake.

If you are a bit high, the rake goes more postive, but the clearance
goes away. If low, the clearance increases but the rake becomes
more negative. When boring or facing this can be used to some
advantage.

It's only three grinds on the HSS tool blank - if you do the
front, and side, but no top grind to form side rake, you've
made a brass turning tool.

Cool! I'll grind the other end of my tool that way and see how it
works out since I have to redo a brass bushing.
Why a flat top on a brass tool? To keep it from pulling itself in?
Are there other materials that would want zero side rake? Is there
perhaps a list somewhere of common materials and appropriate cutter
geometry?

Brass cutting tools really want to have zero rake. But if you think
about it, threading tools and cutoff tools also are run with pretty
much zero rake. If you notice in one of those photos of that small
toolblock above, I have a grooving tool in there, that looks like a
tiny cutoff tool. It works great in steel even though it has *zero*
rake. Key is to keep the tool engagement in the workpiece to a
minimum.

Drilling brass with twist drills meant for steel can cause all kinds of
excitement. The cutting edge is flatted off to make them zero rake
and then the problem goes away.

I've had my share of grinder mishaps. My personal best--or worst--is
getting a bolt I was grinding a flat onto get pulled between the
grinding wheel and rest, taking my finger with it. It finally took
enough flesh off the side of one finger that I could slide my hand out
sideways without getting snagged again. Imagination be damned! I have
first-hand (heh) experience! Whole thing took maybe two seconds. Since
then I've had lots and lots of respect for even wee little grinders. If
the rest has a gap big enough for my finger I either adjust the rest,
remove it entirely, or find another grinder.

This is an OSHA requirment now. Grinders *must* have the rest within
1/16 or so, and they like to see a seconary stop at the top of the
guard as well, so if something gets in there, it won't get spit out
back into the operator. Don't use a machine where the rest is
far away from the wheel.

Jim


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