Subject: Re: Toolpost grinders

From: Charles Lamont <[email-masked]>
Date: 26 May 1995 12:14:58 +0100

> What about a couple of small hand stones held in a manner that let them
> pinch the journal between them and then let the lathe do the work.  It
> would be slow but the results should be accurate.  Has anyone tried
> this?

You are more or less describing 'honing'.  For less than a thou the results
will not be that slow, and it will take practice to get them accurate.

An alternative which is gentler, but still requires the development of some
skill is 'lapping', in which a soft (say copper) split ring is mounted in
something like a die-holder so that it can be closed up, and is charged
internally with an abrasive paste and again run up and down the work in the
fingers.  This is the way a really fine surface and accurate dimensions
can be produced - with practice.

Of course some people just use a bit of wet-or-dry paper in our fingers,
but this is too dangerous to actually recommend.

Another possibility, which again takes time to learn, is to be able to turn
to within 1/2 a thou, which should be good enough for most jobs.  I feel
disappointed if I am not within a couple of tenths on most jobs in
free-cutting mild steel.  
 
-- 
Charles

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From: [email-masked] (J. Kimberlin)
Date: 24 May 1995 16:34:23 -0700

In article <[email-masked]>,
Mike Rehmus <[email-masked]> wrote:
>After looking at four or five tool supply catalogs, I have come to the
>conclusion that I'm missing something about toolpost grinders.
>I know:
>1.  They are very expensive new or used.
>2.  They tend to be very small (3 or 4" wheels)

Catalogues have them all over $1000 for sure.  Only source I know of that 
is reasonable is Sobel Machinery.  They have them usually for under $400.

>What I need to do is take the odd thousandth or less off rod journals
>on a hit'n miss engine I'm building.  Can't cut it off, that does not
>work.
>

What about a small stone in a Foredom handpiece which is locked into a 
small block of lead to dampen any vibrations (and Foredom handpieces 
don't have much vibration to start with).  The lead block could be 
clamped to the lathe saddle - easily if you have a T-slot compound.  I 
have done similar things with a small sanding drum in a Dremel Mototool 
hand held for polishing.  Mototools have too much vibration for really 
fine stone work, IMHO.

Regards,

JerryK

---

From: [email-masked] (Mike Rehmus)
Date: 24 May 1995 22:07:12 GMT

I know:

1.  They are very expensive new or used.
2.  They tend to be very small (3 or 4" wheels)
3.  They are very expensive!
4.  The grinding wheels are insanely expensive  >$50 for a 3 or 4 inch 
   wheel!)

Why?

If we assume the spindles and motors must run true and vibration free,
this doesn't seem like it should cost all that much.

Are there alternatives to a grinder?

I envision a holder that works similar to a 'pliers' knurling tool but
with a holder for each stone that presses the end against the journal. 
Kind of like a brush holder for an electric motor.

Feedback please.

Best,

Mike Rehmus

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From: [email-masked] (Jacob Henteleff)
Date: 25 May 1995 13:57:15 GMT

I think there are alternatives to expensive tool post grinders. I am 
building one of my own. I think it will end up costing about $50.00 when 
I am done and will only make a small dent in the scrap metal collection.

I think the reason the commercial ones are so expensive is:

1.   The castings are relatively complex.
2.   They use very expensive high speed preloaded bearings.
3.   The no load speeds are very high (approx 30,000 rpm)
4.   There is a limited market and those who need the grinders regularly 
will pay the high cost of durable equipment.

There have been some interesting designs for tool past grinders in 
various magazines. The most recent I know if was in Home Shop Machinist 
last year. It uses simple bearings and I think a sewing machine motor. 
The spindle drives a small drillchuck that holds the various stones. 
Speed is kept pretty low on that design so it wouldn't be much good for 
internal grinding.

I am building mine using sintered bronze bushings and drill rod (silver 
steel) for the shaft because of its accurately ground diameter. I am 
hoping heat will not be a problem. We shall see.

As for the idea of using a Dremel tool or Foredom in the lathe, I have 
tried this. There has been a long thread on this in COmpuServe's Metal 
Shop Forum. I find that the finish you get is only fair and not what you 
would hope for in a ground finish. I did, however, successfully grind the 
faces of some valves for a riding tractor lawn mower a year or two ago 
and it worked pretty well.Of course the valves are lapped in on the valve 
seats so perhaps that's not a real test.

Good luck.

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From: "Peter J. O'Leary" <[email-masked]>
Date: 25 May 1995 23:41:06 GMT

An inexpensive alternative to a tool post grinder for removing small amounts of stock is   
a ring lap.  It's better than any other freehand methods because it does not induce out   
of round condition in the workpiece.  Make on as follows: Bore a in a piece of brass the   
diameter of the workpiece.  Drill a small hole adjacent to th first hole.  From the side,   
drill a hole, clear half the depth, and tap the other half.  Make a saw cut from the side   
to the first then to the second hole.  You will now have a sort of squeeze collar that   
you slip over the end of the work.  Apply appropriate lapping compound (I like Clover   
Compound) and run the workpiece at slow speed while traversing the brass lap.  If you   
make the lap out of a longish bar, you can rest it on the compound.  Tighten the screw   
slightly as the lap wears.  If the work diameter is between two shoulders, then you will   
have to split the lap completely in half. 
-- 
Peter J. O'Leary 
Tool & Die Maker

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From: [email-masked] (Mark McDade (303) 673-6841)
Date: Mon, 29 May 1995 14:46:27 GMT

Mike Rehmus ([email-masked]) wrote:
: After looking at four or five tool supply catalogs, I have come to the
: conclusion that I'm missing something about toolpost grinders.

. . .

I bought a $20 air grinder last year, milled a flat along one
side of the body, drilled and tapped it and mounted it on my
cross slide.  It's horribly slow but produces a nice finish on
TINY amounts of metal removal.

Mark McDade

mark_mcdade

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From: [email-masked]
Date: 28 May 1995 23:18:28 GMT

> Try calling Machinery Dealers National Association in Silver Spring, MD.
They are the national trade association of used machinery dealers, and 
give out a free membership directory that lists the members by their 
specialties.  It's called the Buyer's Guide.  You can get one by calling
Sharon or Jeannie at 301-585-9494, and tell them you read it from me
on the NET.  I'm trying to get enough calls in there to convince them to
go on line.
	Good luck.
Mark Rogo, Morton Machinery Company, Los Angeles CA.