Subject: Re: Ready made spacers?

From: [email-masked] (Jens)
Date: Sun, 08 Dec 1996 22:45:31 -0800

Don't know about this first hand but my way of tackling that would be
to take some standard spacers (or turn some), mount them on a plate
that has been surfaced parallel on the two flat sides and then machine
the length all at the same time (either lathe or mill).
The spacers would be mounted from below with bolts (or you could
machine them with studs on them and bore them out after the length has
been dealt with.)

Jens

---

From: "Steve Stallings" <[email-masked]>
Date: 10 Dec 1996 15:25:51 GMT

Jonathan M. Elson <[email-masked]> wrote in article
<[email-masked]>...
> [email-masked] wrote:
> : G'day,
> 
> : Does anyone have a neat suggestion for some spacers. I am mounting
three
> : NEMA-43 motors and I need some spacers 1.000" long with at least a 1/4"
> : diameter hole through them.
> 
> : Since they are motor mounts they must all be *exactly* the same length.
I
> : don't have a surface grinder and it is proving a chasing game to
machine
> : them to the exact same length in the lathe. 
> 
> Gee, why?  I do this all the time, and usually get it to +- .005" without
> even trying.  I'm sure I could get it to +- .001" without a lot of hard
> work.  How exactly do you need them?  Are you sure that the motor housing
> is cut to that kind of accuracy?  I see people doing this kind of stuff
> all the time.  Grind the spacers to +- .0001", finish them like gage
blocks,
> and then put them on a motor that is built with tolerances of .010".
> 
> 						Jon
> 
> 
I assume that Peter is concerned about mounting stepper motors such
that the shaft of the motor is exactly in line with the driven shaft.
It is indeed tricky business and is usually avoided by using a flex
coupling or a belt drive system. High torque flex couplings suitable 
for pecision work can cost over $50 each.

If you need spacers that are the same length but the exact length is
not critical try this: Surface finish both sides of a block large
enough for four spacers. Drill the four holes; THEN cut it into four 
pieces and do any additional work required for the final shape.

Steve Stallings
[email-masked]

---

From: Jay Hayes <[email-masked]>
Date: Wed, 11 Dec 1996 20:25:02 -0800

[email-masked] wrote:
> 
> In article <[email-masked]>, "Bill
> Harnell" <[email-masked]> writes:
> 
> >This will allow you to lock the carriage on the ways,
> >insert the stock into the lathe chuck, face off the initial
> >surface, set the parting tool at the cutoff position
> >desired, reposition the stock until it hits the stop,
> >retract the tailstock a specific distance to permit parting
> >off without damaging the part or the stop, repositioning
> >the tailstock, etc., etc., and then drilling the 1/4 inch
> >hole you require in each part.
> >
> >
> 
> Didn't try this, but as I have responded to Fitch even 0.0015 at the bolt
> circle diameter gave a significant angular displacement, binding the lead
> screws.
> 
> Thanks anyway, I suspect I'll have to spring for the couplings.
> 
> Peter

Peter instead of using four presision spacers, could you use a one inch
section of 3 - 4 OD tubing with the ends machined (turned) parallel. You
could drill a hole in the side of it to access the set screws in the
coupling if necessary or just cut a section of it out.

Another trick, if you've got four soft spacers (aluminum or brass) that
are all within a couple of thousandths of each other, lay them next to
each other inline with the screw in the center of your machine vise and
crush them till they are all tight.

If you need thousands of them I could injection mold them for you.

Hope this helps,

Jay

---

From: [email-masked] (Fitch R. Williams)
Date: Wed, 11 Dec 1996 06:27:27 GMT

[email-masked] wrote:

>In article <01bbe6ac$d2655400$015cefce@scshome>, "Steve Stallings"
><[email-masked]> writes:

>You were indeed correct about the need for accurate spacers, I am trying
>to do away with the $67 non-backlash high-torque, flex couplings for
>direct drive.

>As to your suggestion for the block, now that *is* a cool idea. The blocks
>will be under a metal chip guard so no-one gets to see they have been
>bandsawed off.

>Peter

Yes.  I'd probably just buy a piece of 1" X 1" precision
ground stock, drill holes in it, and saw off some pieces.

Or, if you have a piece of 1" rod, and really want to make
them round, I would try the following.  

Cut  roughly to length and face one end of all of them but
leave +.010 of extra length.  

Drill them all in the lathe, and then set up to face them
off all at one setting.  

To face to final length, use a block (precision parallel
works well) across the chuck to locate the first one in the
chuck (after tightening the chuck on the work, remove the
parallel!), position and lock the carriage, tighten the gibs
on the compound, use a carbide insert tool (to get
repeatability if the bit gets dull or somehow damaged) and
then face them off one at a time.  Leave everything alone
between pieces.  Stop the lathe,  loosen the chuck to slide
the work back from the cutter, backup the cross feed, remove
the work, and chuck the next one using the exact same
locating block (parallel).  

Should be good to .001 repeatability in length.  If you work
carefully, you can probably get them to 1" plus or minus
0005.  

Fitch

---

From: "Bill Harnell" <[email-masked]>
Date: 11 Dec 1996 06:30:16 GMT

Perhaps I'm being naive, but . . .

If your headstock will permit passage of stock of the
diameter which you wish to make the spacer of, can't you
use your tailstock as a "stop"?

I'm assuming, of course, that the tailstock is equiped with
a calibrated thimble for positioning purposes. Mine is and
I use this precedure frequently for making parts of
identical length.

Even if your tailstock is not calibrated, it is simple
enough to clamp a stop to the ways (to which your tailstock
can be butted) to accomplish the same purpose.
-- 
Bill Harnell [[email-masked]]

[email-masked] wrote in article
<[email-masked]>...
> G'day,
> 
> Does anyone have a neat suggestion for some spacers. I am
mounting three
> NEMA-43 motors and I need some spacers 1.000" long with
at least a 1/4"
> diameter hole through them.
> 
> Since they are motor mounts they must all be *exactly*
the same length. I
> don't have a surface grinder and it is proving a chasing
game to machine
> them to the exact same length in the lathe. 
> 
> I thought of using hardened drill bushes but the ones I
have measured vary
> in length by several thou. Any suggestions for an
off-the-shelf item that
> would work? They can be square round hex, anything as
long as the length
> is consistant with a 1/4" or larger hole through them.
Hell the hole can
> even be off-center.

---

From: [email-masked] (Alan Shinn)
Date: Wed, 11 Dec 1996 22:40:49 -0800

You could press 7 spacers into a thin walled tube and then face both ends
of the conglomerate in your lathe--they aughta be pretty close to one
another that way.

-- 
Al Shinn   (Tinker)
alshinn@ sirius.com

---

From: [email-masked]
Date: 9 Dec 1996 17:09:53 GMT

G'day,

Does anyone have a neat suggestion for some spacers. I am mounting three
NEMA-43 motors and I need some spacers 1.000" long with at least a 1/4"
diameter hole through them.

Since they are motor mounts they must all be *exactly* the same length. I
don't have a surface grinder and it is proving a chasing game to machine
them to the exact same length in the lathe. 

I thought of using hardened drill bushes but the ones I have measured vary
in length by several thou. Any suggestions for an off-the-shelf item that
would work? They can be square round hex, anything as long as the length
is consistant with a 1/4" or larger hole through them. Hell the hole can
even be off-center.

Peter

---

From: [email-masked]
Date: 11 Dec 1996 17:34:45 GMT

In article <[email-masked]>, [email-masked] (Fitch R.

>carefully, you can probably get them to 1" plus or minus

Yeah, that's where I started Fitch, I managed about 0.0015 but it was
enough to load the lead screw slightly. That 0.0015 at the bolt circle
diameter of 4-1/4 (I think without going an measuring) translated into a
significant angular displacement. May have to pay the money for those
couplings yet.

Peter

---

From: Steve Austin <[email-masked]>
Date: Thu, 12 Dec 1996 20:11:59 -0500

Lee Marshall wrote:
> 
> Jonathan M. Elson wrote:
> >
> > [email-masked] wrote:
> > : G'day,
> >
> > : Does anyone have a neat suggestion for some spacers. I am mounting three
> > : Since they are motor mounts they must all be *exactly* the same length. I
> > : don't have a surface grinder and it is proving a chasing game to machine
Got a surface plate and height gage?  How about a lapping plate?
Once the pieces are machined to length you can work the ends on a
piece of sandpaper laid on some flat surface.  By checking on the
surface plate you should be able to get them within a few tenths.
The lapping plate should finish them as close as you can measure.
Steve A.

---

From: [email-masked]
Date: 11 Dec 1996 17:34:49 GMT

Peter

---

From: [email-masked]
Date: 13 Dec 1996 16:39:50 GMT

In article <[email-masked]>, Steve Austin
<[email-masked]> writes:

>S

Steve, thanks for the suggestions but I suspect the hand finish on
sandpaper would affect the perpindicularity (is there such a word) and
just exacerbate the problem.

As you have no doubt read by now from another post the solution was too
easy. I missed it completely until it was pointed out *twice* to me.
Sometimes I am just *too* thick! <g>

Peter
Who'se forehead continues to slope further back from constant slapping.

---

From: [email-masked] (Fitch R. Williams)
Date: Thu, 12 Dec 1996 05:47:52 GMT

>Peter

OK, I understand.  You are talking about the coupling
between your 1125 in-oz motors and the mill leadscrews.  The
couplings are that expensive because you need zero backlash.

One at a time doesn't work, so how about doing them in
bunches?  Just thinking "out loud" here.  Is there any way
to bundle them all up on a faceplate and machine them all at
once?  could you, for example, drill the center hole
oversize, thread it, and bolt them to the face plate from
the back side in groups of four, and face them off all at
once?  Do the same thing on a ground piece of flat stock and
flatten them in the mill four at a time with a fly cutter,
2" face cutter, or some sort of grinder mounted to the head?
Mounted on a shaper table with a grinder mounted on the ram
in place of the usual cutting tool - but use the hand wheel
to stroke it back and forth?  Find a surface grinder and
grind them four at a time while they are standing at
magnetic attention on a magnetic chuck?

You've probably tried all these already.  Oh well, I'll keep
thinking.

Fitch

---

From: [email-masked] (James Wilkins)
Date: Thu, 12 Dec 1996 14:32:41 -0400

> is consistant with a 1/4" or larger hole through them. Hell the hole can

How about cutting up a set of the cheap Enco 1-2-3 blocks?

-- 
James Wilkins
The Mitre Corp.
Bedford, MA

---

From: [email-masked]
Date: 12 Dec 1996 20:07:03 GMT

In article <[email-masked]>, [email-masked]
(Jonathan M. Elson) writes:

>motor's bearings.  You can mount a gear or belt pulley rigidly on a
>motor, but except in very unusual situations you should avoid rigid
>coupling a shaft to a motor.  The one place it is accepted is if the
>motor turns a thin shaft, which can flex to absorb angular and radial
>misalignment.  Then, however, you must accept a speed limitation on
>the motor/shaft, because this is a perfect setup to excite vibrations
>in the thin shaft.  Machine tool axis drives usualy turn slow enough
>to be well below critical speed.
>	

If the motors were turning at any apprecianble speed then perhaps you
might be right, these are stepper motors and I doubt they will  be much
above about 300-500 and rarely at that.

Peter

---

From: [email-masked]
Date: 13 Dec 1996 03:39:19 GMT

Ok I finally clicked as to what might work for you. As far as the spacer
goes I would probably try the pipe method. But I just remembered how I
made a flexible coupling for a sander. I'm not real sure if this will be
stiff enough for this application but you might remember it for somthing
else. What I did was make two sleeves about 2" long and 1 1/4" dia.  one
for the motor and one for the sander. I turned about 1" down to where it
would be a very tight fit on a piece of stiff one inch hose that I had. I
then knurled the place that the hose would slip on. What I did was add
about 3 or 4" of hose to the sleeves and used wire wrapped and twisted
tight for the hose clamps. Voila one flexible coupling that didn't cost a
penny. What I'm thinking is that if you can find a piece of rubber or
extra thick hose making it about 1" or 2" in diameter. And if you keep the
two sleeves really close there really wouldn't be that much flex to the
whole thing. But maybe there would be just enough to allow free operation
without being too flexible on the rotation. Somthing like hydraulic hose
would be pretty stiff but I don't know if it would work. You would still
need to keep the shafts lined up as close as possible but you could
probably be off as much as a thousandth or so and it still work. 

 I have also come across somthing that could be made in the home shop
fairly simply that might do the trick. It might be a little hard to
describe but if you will give me a little while I will try to come up with
something.

   Wayne Cook

Quality is like buying oats,
        if you want nice, clean, fresh oats you must pay a fair price.

However, 
        if you can be satisfied with oats that have already been through
the horse...
                          
That comes a little cheaper...

---

From: [email-masked] (David Erickson)
Date: 12 Dec 1996 23:54:07 GMT

In article <[email-masked]>,

>: Yeah, that's where I started Fitch, I managed about 0.0015 but it was
>: enough to load the lead screw slightly. That 0.0015 at the bolt circle
>: diameter of 4-1/4 (I think without going an measuring) translated into a
>: significant angular displacement. May have to pay the money for those
>: couplings yet.

>If .0015" does not allow the motor to turn the shaft/screw smoothly, you
>shouldn't be using a hard, direct coupling.

I agree with Jon, but I also would suspect that you have an alignment
problem other than the .0015" difference in spacer height.  When you
move the spacers around,  does the tight spot remain in the same place?
Does the location and tightness of the fit vary depending on how much
the screw is driven into the nut?   Are the motor and the nut aligned?
Is the leadscrew bent?

Dave

--
-----------------------------------------------------------------------------
David Erickson    Technical Support Engineer    Rational Software Corporation
email: [email-masked]
-----------------------------------------------------------------------------

---

From: [email-masked]
Date: 13 Dec 1996 16:39:45 GMT

In article <[email-masked]>, [email-masked]

>How about cutting up a set of the cheap Enco 1-2-3 blocks?

I love this group! Neat idea but the problem is now solved. I am bolting
them to a face plate and turning them in sets of four. Good idea though. I
thought 1-2-3 blocks would be hardened but maybe some of the cheaper ones
aren't.

Peter

---

From: [email-masked]
Date: 13 Dec 1996 16:39:47 GMT

In article <[email-masked]>, [email-masked] (David

>the screw is driven into the nut?   Are the motor and the nut aligned?

Scuse me guys but we aint talking watch machining equipment here. The lead
screw is 5/8 and so is the shaft on the motors. These are 1125oz-in
NEMA-43 motors! The only flexing here is my muscles to lift them.

0.0015 difference in height of the spacers *will* bind these suckers.

Peter

---

From: [email-masked]
Date: 13 Dec 1996 17:26:51 GMT

>describe but if you will give me a little while I will try to come up
with

Thanks Wayne, I have resolved the problem by bolting the spacers to a
faceplate and machining in sets of four. However I had started thinking
about a flexible coupling. I am investigating something along the lines
you have deescribed but using a hefty compression spring instead of hose.

The spring I am trying is very very stiff but it flexes longitutudinaly
reasonably easily. I am hoping this will give me a fixed rotational drive
but allow for misalignment.

More later after I apply power to the steppers to see if one inch equals
one inch.

I'd be interested to hear about the 'other' method too. Maybe a rough
sketch in Paintbrush and attach to an email.

Peter

---

From: [email-masked]
Date: Fri, 13 Dec 1996 13:32:59 -0500

>  diameter hole through them.

[big snip]

A wise old philosopher once suggested even a fish wouldn't get in
trouble if he kept his mouth shut, perhaps I should follow that advise
but I can't help but wonder out loud about this problem.  Why, one would
not use some shim stock in conjunction with some undersized and less
than perfect spacers to bring the motor into alignment? My guess is that
the motor mounting flange is no better than +/- 0.005" under the best of
circumstances so what good is a spacer that's +/- 0.0000000? 

Is there something I'm missing. 

pht
curious to know

---

From: [email-masked] (Randolph Lee)
Date: Fri, 13 Dec 1996 14:13:46 -0400

the method of clamping them all to a (freshly faced face plate and don't
take it off after facing to attach the blanks for top accuracy) lathe face
plate will work, 

but don't foget that most lathes (even a top qual machine like a Schaublin
of Hardinge or Leven)  will face very slightly concave... per the
Sleschinger (sp) limits. my Schaublin 102 is concave 0.0001 mm accross a
150 mm face plate on the test sheet that was made when it was built... ( I
can not measure that finely with my metrology equipment... I get .000mm
with no flicker going from my grade 2 gauge blocks on my surface plate
accross the face plate). which scould be good enough... My Atlas on the
other hand is 0.0007" concave accross a 9" face plate almost a thou low.
your lathe may vary and remember you can not check this by mounting an
indicator in the tool post an traverseing the mounted plate... a quick and
dirty check is with a known good straight edge and a loog for a line of
light... or try a .0005 feeler gauge under the middle..

Randolph Lee
Windshadow Engineering

---

From: [email-masked] (Gavin Donahue)
Date: Fri, 13 Dec 1996 01:45:25 -0700

> the screw is driven into the nut?   Are the motor and the nut aligned?
I think it would be a false economy to omit the flexible coupling. But
maybe a suitable coupling could be made by selectively weakening a
standard solid part since the load is relatively light. Is there room to
turn it into a hourglass shape, or maybe opposing kerfs repeated with each
pair rotated 90deg. Of course this better accommodates angular than axial
misalignment.

---

From: Bart Smaalders <[email-masked]>
Date: Fri, 13 Dec 1996 15:19:07 -0800

[email-masked] wrote  about trying to machine spacers accurately...

Why not just hang the motor off of it's output shaft with a rigid
coupling, and put a torque arm (out of say 1/4" Al) back to something
solid.  The motor won't move, and no fancy technology is required.

The bearings need to be able to take the weight, but then, that's
not asking a lot...

- Bart

-- 
Bart Smaalders			Solaris Clustering	SunSoft
[email-masked]		(415) 786-5335		MS UMPK17-301
http://playground.sun.com/~barts			2550 Garcia Ave
							Mt View, CA 94043-1100

---

From: [email-masked] (Fitch R. Williams)
Date: Fri, 13 Dec 1996 06:35:05 GMT

I didn't know they were that close in size.  <G>

Actually, its a good idea.  I will keep it in mind.

Fitch

---

From: [email-masked] (Jonathan M. Elson)
Date: 14 Dec 1996 05:43:57 GMT

[email-masked] wrote:
: In article <[email-masked]>,
: [email-masked] writes:

: Thanks Wayne, I have resolved the problem by bolting the spacers to a
: faceplate and machining in sets of four. However I had started thinking
: about a flexible coupling. I am investigating something along the lines
: you have deescribed but using a hefty compression spring instead of hose.

: The spring I am trying is very very stiff but it flexes longitutudinaly
: reasonably easily. I am hoping this will give me a fixed rotational drive
: but allow for misalignment.

The standard shaft coupling for precision leadscrew drive is a solid block
of metal, often aluminum, which is bored through for the shaft diameter.
Then, the center section is cut in a way that allows the necessary flexing
while retaining rotational stiffness.  One favored way is to cut a helical
slot that runs for at least five turns all the way to the center bore.
You can look in Stock Drive Products, W.M. Berg or other catalogs and see
excellent pictures of these, probably in smaller sizes than you need.
Another design uses alternating straight cuts that leave enough material
for strength.  This would be easy to make with a jeweler's saw in the
mill.  The helical cut is a little trickier, but I think it could be done
with a thin abrasive cutting wheel in a tool-post grinder on the lathe,
or free hand on a bandsaw.
I'm afraid your spring might not be stiff enough, and getting it aligned
properly when attaching to the shaft collets is going to be tricky.
Keep us posted on how it goes.
						Jon

---

From: [email-masked] (Jonathan M. Elson)
Date: 12 Dec 1996 06:00:08 GMT

[email-masked] wrote:

If .0015" does not allow the motor to turn the shaft/screw smoothly, you
shouldn't be using a hard, direct coupling.  There are good couplings
made for both angular and radial misalignment.  Even if you replaced these
spacers with guage blocks, why do you think the shaft would then turn
without binding?  (I bet it would not.)  In any assembly of this sort,
where the motor shaft is beefy enough that it would not deflect, and
the driven shaft/screw is stiff enough to not bend, a coupling is
always used.  If you don't, the constant flexing will loosen any hard
coupling you could get, or even crack the motor shaft or damage the
motor's bearings.  You can mount a gear or belt pulley rigidly on a
motor, but except in very unusual situations you should avoid rigid
coupling a shaft to a motor.  The one place it is accepted is if the
motor turns a thin shaft, which can flex to absorb angular and radial
misalignment.  Then, however, you must accept a speed limitation on
the motor/shaft, because this is a perfect setup to excite vibrations
in the thin shaft.  Machine tool axis drives usualy turn slow enough
to be well below critical speed.
					Jon

---

From: GEMARS <[email-masked]>
Date: Fri, 13 Dec 1996 10:23:19 -0800

Lee Marshall wrote:
> > even trying.
> A relatively simple method of acheiving repeat length on a lathe is to
> place a spider plate on the face of the chuck (presuming that you don't
> have a collet setup). This is a three fingered plate that goes between
> the chuck jaws and gives you a known position against which to put the
> work piece. If the part is too short to protrude past the tips of the
> jaws, you will have to add a threaded hole for an adjusting screw to
> become the back stop.
> You can either use a carraige stop to the ways, or simply not move the
> carraige for the three spacers that you want to machine.
> 
> While this is a pretty simple operation for many of us, it may be
> something that has never been attempted by others. Let's all try to help
> each other out, rather than trying to denigrate someone's lack of
> knowledge.
> Lee Marshall
> Bonny Doon Engineering     http://www.bonnydoonengineering.com

Damn nice attitude!! GW, beginner

---

From: [email-masked]
Date: 14 Dec 1996 15:52:14 GMT

>Is there something I'm missing. 

Too much messing around with shims. The NEMA-43 is face mounted not foot
so the perpindicularity (such a word?) of the spindle to the face is way
better than 0.005" Machining the spacers on the face plate at the same
time solved the problem. Once I got the radial alignment ritght I
tigthened everythinup and it works fine.

I will still consider a flex coupling of some sort althout the DC servo
motors that came with the mill were direct coupled exactly as I am doing
the steppers. Only difference is the steppers have .625 shaft and the
servos had .500 so I have had to make an adaapeter that set the stepper
out another inch further thus requiring the spacers.

Peter

---

From: [email-masked]
Date: 14 Dec 1996 15:52:17 GMT

>The bearings need to be able to take the weight, but then, that's

Perhaps a quick check back to my original post would reveal these are
1125oz-in NEMA-43 motors. They weigh over 40 lbs each with a 5/8 shaft.
They are almost a foot long.

No mount and a torque arm, I don't think so Tim, :)>

Peter

---

From: Steve Austin <[email-masked]>
Date: Sat, 14 Dec 1996 23:52:56 -0500

Randolph Lee wrote:
ther hand is 0.0007" concave accross a 9" face plate almost a
thou low.
> light... or try a .0005 feeler gauge under the middle..
If you run your indicator across the half of the plate towards
the back side of the lathe will read twice the dish.
Steve A.

---

From: [email-masked] (Dave Ide)
Date: 14 Dec 1996 13:55:33 GMT

Randolph Lee ([email-masked]) wrote:
: of Hardinge or Leven)  will face very slightly concave... per the
: Sleschinger (sp) limits. my Schaublin 102 is concave 0.0001 mm accross a

     The what kind of limits?
     David Ide

---

From: [email-masked] (Reckless)
Date: Sun, 15 Dec 1996 06:01:30 GMT

>Peter

You've probably already solved your problem by now, but a flexible
coupler can be made by cutting an X shaped piece of metal (spring
steel comes to mind) and bending the arms such that the north and
south arms point down and the east and west arms point up.  The arms
would then be attached to hubs, one on the motor shaft and the other
on the leadscrew shaft.  If the arms are wide enough, there would be
very little rotational play, and it could accomodate several thou
worth of angular or radial displacement.  I seem to remember seeing a
part like this in a mechanical cash register or something similar, on
the motor shaft.

The rubber hose on 2 hub couplers are a great idea, and if you can get
a hose with outer braid and clamp the braid well enough, it will
transfer torque quite nicely.  Just remember to pull the braid tight
before clamping it.

Just some more thoughts,
-Reckless

---

From: [email-masked]
Date: 15 Dec 1996 17:34:47 GMT

>transfer torque quite nicely.  Just remember to pull the braid tight

Thanks to all, this has been a very long and sometimes interesting thread.
BillG has sent me a CAD drawing of a simple design that looks like it will
work well. I'll make one of these and try it.

Peter

---

From: [email-masked] (Randolph Lee)
Date: Sun, 15 Dec 1996 14:18:14 -0400

>: Sleschinger (sp) limits. my Schaublin 102 is concave 0.0001 mm accross a

David, the (sp) after the spelling used above means that I misspelled it
and I knew it was misspelled but that I thought it was close enough for
most folks to know what I was writeing about... sorry it was lazy of me not
to look it up.

the word is Schlesinger, and the Schlesinger Limits are named after Dr.Ing
George Schlesinger he was a cofounder of the german standards inst. in 1917
and developed the Machine tool inspection standards used worldwide and
hence named after him... for full details read his 1927 Tome "Machine tools
Inspection book" or the 1978 revised edition ISBN 0-08-021685-4 Pergamon
press.

the limit in question in the thread (cross slide at right angles to
spindle(to face flat or concave only)) is 0.001 in/ft. on a finishing lathe
up to 16" center height and 0.0008 in/ft. on an instrument lathe of the 50
to 140mm center height size

a full treatment dumbed down to my level is in a current series titled
"Testing and Alignment of Centre Lathes" in ME (started in the 4th Oct 96
issue and I would not be supprised to see it become a future book in the
workshop practice series... it is written by perhaps the best living ME
author Tubal Cain (T.D. Walshaw) and it is keeping me waiting for the next
issue and instalmnet,

Randolph Lee
Windshadow Engineering

---

From: [email-masked] (Milt Carlson)
Date: Sat, 14 Dec 1996 15:07:51 GMT

>Keep us posted on how it goes.

How would a u-joint work. Not with bearings but like the old style
with a round flat belting material between two yokes that are offset
ninety degrees. Don't  use a belt but a springy thin steel disk.

Milt