Subject: Homebrew lathe toolpost grinders?

From: [email-masked] (John Cooper)
Date: Sun, 23 Jan 1994 23:45:13 GMT

Looking at the cost of toolpost grinders made me wonder if there might be an
el-cheapo alternative for occasional use.  Maybe a dremel mounted in/on the
post?  Any guess if standard stones would work?  I've seen setups similar to
what 'looks' like a dremel tool used to grind interior tapers.  I assume any
slop in the bearings would factor out if the stone was fed slow enough...
Any thoughts/suggestions welcome.

-john

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From: [email-masked] (Greg Lewis)
Date: Mon, 24 Jan 1994 20:51:28 GMT

>Any thoughts/suggestions welcome.

I seem to recall an ad in Home Shop Machinist for a kit. Several
castings were provided. I cant remember the company... perhaps Metal
Lathe Accessories? I tried my Dremel and found the spindle not tight
enough... the grinding wheel bounced around too much. Check HSM
magazine from about two or three years ago... I think thats when the
ad ran.

___________________________________________________________________
[email-masked]
Photojournalism sequence, Department of Mass Communication and Journalism
CSU Fresno, Fresno, CA 93740-0010

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From: [email-masked] (John Wishneusky)
Date: Mon, 24 Jan 1994 14:50:22 GMT

>Any thoughts/suggestions welcome.

I've a simple, homemade lathe toolholder system to which it was easy to
add an adapter to hold a 1" diameter Foredom handpiece.  I did this
when I needed to grind new top-jaws I bought for the 3-jaw chuck that
was included with the 11" Logan lathe I bought years ago.  The
replacement jaws were a perfect fit to the lower pieces that engage
the scroll, but the amount of slop in the fit of the lower jaw pieces
to the channels they ride in allowed the jaws to splay open so much as
to render the chuck useless.  To cure this, I loaded the jaws in a
clamping position and used the Foredom in lieu of a toolpost grinder
to grind the jaws true to the lathe axis.  I've been extremely happy
with the results.

The short answer is I had success with a similar setup to what you'd
like to try.

John

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From: [email-masked] (Bill W. Martin)
Date: Mon, 24 Jan 1994 17:26:20 GMT

In article <[email-masked]> [email-masked] (John Cooper) writes:
>From: [email-masked] (John Cooper)
>Subject: Homebrew lathe toolpost grinders?
>Date: Sun, 23 Jan 1994 23:45:13 GMT
	A small air driven grinder might do what you want, I doubt if a 
dremel-type tool will give you enough rpm's to do things like interior 
tapers. On the subject of stones and bearings, etc... Air grinders need very 
high-speed rated stones, and no, bearing slop wont go away...it shows up as 
a "wavy" look and rather un-smooth finish on the ground surface. Wich means 
you need a spindle with GOOD bearings to do decent grinding.
bill

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From: [email-masked] (David Jenkins)
Date: 25 Jan 1994 15:52:49 GMT

If you have the opportunity to look through old UK Model Engineer
magazines, you should find references to "Potts spindles" designed
specifically for drilling and grinding from the cross-slide, for
working on pieces held in the chuck.  You might find them in E.T.
Westbury or George Thomas books by the same publishers.

These are simple devices, basically a spindle running in two good
bearings, with a chuck on the front and a pulley on the back, driven
by a belt-drive.  This is either mounted on a pivoted stand, or
something more rigid mounted on a vertical slide (for simple
adjustment).

This is one of those round-to-it jobs I keep meaning to do...
 
-- 

David Jenkins

* I'd rather be steaming... *

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From: [email-masked] (Ron Ginger)
Date: 25 JAN 94 13:46:09

In article <[email-masked]>, [email-masked] (John Cooper) writes...
>Any thoughts/suggestions welcome.
I made a simple wood block to hold my Dremel on the cross slide. It works, but
a Dremel is not very powerfull and rather poor bearings- you never notice how
poor while hand holding the thing, but when its ridgidly held its a problem.
I did use this to true up the jaws of an old 3 jaw chuck.

Ive almost orderd a die grinder from Harbor Freight, which notes it has a 
cylindrical nose suited to clamping as a toolpost grinder. Most of the
die grinders have tapered noses that would be hard to mount.

Has anyone used teh Harbor Freight die grinder?

ron

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From: [email-masked] (Stuart Friedberg)
Date: Wed, 26 Jan 94 03:21:12 GMT

>poor while hand holding the thing, but when its ridgidly held its a problem.

I just went through this last weekend.  I needed to do some circular
milling, had no rotary table, so used my lathe spindle as the mount
and used a Dremel 395 as a "toolpost miller".

I discovered the slop from side to side is not in the bearings per
se.  The bearings are rather nice, actually, and there are two on
the collet shaft, not even counting the ones on the motor.  The
problem is that the collet shaft bearings sit in simple molded
plastic recesses and there's considerable slop.  In fact, I suspect
this is why the bearings will whine at certain speeds: they're
actually spinning in the recesses until they "grab" hold.  I didn't
stop to fix things thoroughly, but simply padded the recesses with
a couple of shims cut from a 3x5 card.  That reduced the deflection
to something I was willing to live with.

>I did use this to true up the jaws of an old 3 jaw chuck.

That's the first thing I did with the Dremel on the lathe. :-) I
was using sufficiently light cuts that I didn't notice the deflection
at all.  (Not that it wasn't there, just that I didn't notice.)

Last Saturday, I was making an adaptor for a Bosch router to take
Porter-Cable template bushings, and had to cut several recesses
along the rim of a disk.  I quickly noticed the Dremel's deflection
when pushing the cutter into the work.  It was rather excessive:
about 3/32" at the base of the collet, quite a bit more at the cutting
tool!

By the way, I suspect the Dremel was *designed* to have a considerable
amount of slop.  There's a neat automatic clutch made from a piece of
plastic tubing with internal splines, and lots of other features to
"give" under the abuse of a ham-handed user.

Stu Friedberg ([email-masked])