Extending lathe spindle
Ignoramus27446
It is a totally great lathe, but 4-5 inches near the chuck are very
worn and result in 0.008" taper of test pieces that I machined.
I thought, perhaps, that I could use an L0 plate, and a 6" round piece
of something (like a cast tube or aluminum tube) to extend the plate,
and then to put on a plain back chuck.
/|~~~~~~~~|===\
======== | tube | \
======== | |chuk/
spindle \|________|===/
^
L0 plate
"chuck" misspelled as "chuk" to fit the word in
Has anyone ever considered doung so.
Jim Wilkins
27446.invalid> wrote:
> I was thinking with sadness about my Clausing lathe.
>
> It is a totally great lathe, but 4-5 inches near the chuck are very
> worn and result in 0.008" taper of test pieces that I machined.
> Has anyone ever considered doung so.
I bought a scrapped lathe's headstock to temporarily clamp onto the
ways further down where the leadscrew isn't worn, or to block up for
larger diameters.
jsw
Ivan Vegvary
"Jim Wilkins" <kb1...@gmail.com> wrote in message
news:885bc600-92e8-4e69...@t42g2000vba.googlegroups.com...
I bought a scrapped lathe's headstock to temporarily clamp onto the
ways further down where the leadscrew isn't worn, or to block up for
larger diameters.
jsw
Jim, I was thinking around the same lines. Can one simply relocate the
headstock futher down the bed?
Ivan Vegvary
spaco
On a 2" diameter piece in the lathe, a 1/16"(that's HUGE) drop in
the cutting tool would only cause a one thousandths taper (2 thou on the
diameter), the end toward the headstock being larger because of it.
Dropping a whole 1/8" causes a 3.8 thou taper (7.6 thou on the
diameter). Things get worse faster after that, of course.
But, since you say the wear is only 4-5 inches long, the effect of
any drop would only be about 1/2 anyway, because the saddle would
average the error out,
To measure this, I constructed the above on my cad program. I think I
got it right, but you might want to wait for some more expert folks to
reply.
Pete Stanaitis
------------------------------------------------
Ignoramus27446
> I don't think your worn lathe bed is at the root of your taper problem.
> On a 2" diameter piece in the lathe, a 1/16"(that's HUGE) drop in
> the cutting tool would only cause a one thousandths taper (2 thou on the
> diameter), the end toward the headstock being larger because of it.
> Dropping a whole 1/8" causes a 3.8 thou taper (7.6 thou on the
> diameter). Things get worse faster after that, of course.
Pete, the saddle rides on "inverted vee ways", and the inclining parts
of the vees are worn. I can see and feel that wear.
i
DoN. Nichols
It depends on the design of the lathe.
My Clausing (Model 5418 -- 12x24") has the motor and
countershaft in the pedestal below the headstock, and there are notches
cut in the ways to clear the belts going down from the spindle to the
countershaft. This would not accept moving the headstock along the bed,
and there is a taper pin to lock the position of the headstock on the
bed.
But -- if your lathe has a motor and countershaft hinged off the
back of the bed, that is a different matter -- and your only worry would
probably be deflection of the ways with no support feet under the
headstock. Some of the Clausings of the same basic model -- but made
for bench mounting -- are powered in just that way.
Enjoy,
DoN.
--
Email: <dnic...@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
Harold & Susan Vordos
"Ignoramus27446" <ignoram...@NOSPAM.27446.invalid> wrote in message
news:z6adnfsxsri9QqrW...@giganews.com...
Extending the spindle will yield a machine that has no rigidity. Chatter
will be a constant problem.
Harold
spaco
still apply? I'd think you could test this thinking by clamping an 8
or 10 inch long flat plate to the back of some machined bed surface and
then putting a dial indicator on your longest boring bar to test for
sideways movement of the saddle as you traverse the bad area. If the
saddle is moving sideways, then I see the problem.
Wait a minute. Mount a known cylindrical bar in the lathe. Make it
as long as you can. Run all the way along it with a dial indicator. If
the worn ways ARE the problem, then you should have NO taper at the
tailstock end. The tapering should only start when the left edge of the
saddle gets to the wear area. If this is true, I am wrong and will
never bother you again on this issue.
Pete Stanaitis
----------------
Karl Townsend
"spaco" <sp...@baldwin-telecom.net> wrote in message
news:JsSdnfLozb4SfaXW...@bright.net...
>I see, but if the wear is DOWN not sideways, shouldn't these numbers still
>apply? I'd think you could test this thinking by clamping an 8
actually the math works the other way. A little loose up/down lets the
carriage slide way back. IMHO extending the chuck will cause more problems
than it solves.
Karl
Ignoramus4115
> still apply?
The wear is on the vees and it lets the carriage move sideways.
I have some other possibilities that I am considering.
i
whit3rd
wrote:
> On 2009-12-28, spaco <sp...@baldwin-telecom.net> wrote:
> > I see, but if the wear is DOWN not sideways, shouldn't these numbers
> > still apply?
>
> The wear is on the vees and it lets the carriage move sideways.
So, the wear is on one side only of the vees? Gravity will keep the
carriage centered if both sides are worn equally.
> >> Pete, the saddle rides on "inverted vee ways", and the inclining parts
> >> of the vees are worn. I can see and feel that wear.
You can 'see and feel' microinches of surface finish, too. It would
be best to measure the wear and do the calculation before doing
an expensive rebuild.
Mark Rand
<ignora...@NOSPAM.4115.invalid> wrote:
>
>The wear is on the vees and it lets the carriage move sideways.
>
>I have some other possibilities that I am considering.
>
Long term fix is to save up the pennies and have the bed re-ground. In the
meantime, practice scraping to the point where you have no qualms about
scraping the carriage and tailstock to fit the re-ground bed.
Short term fix. Live with it. Extending the mandrel will introduce you to a
world of pain that you don't need.
Mark Rand
RTFM
whit3rd
wrote:
>
> > I see, but if the wear is DOWN not sideways, shouldn't these numbers
> > still apply?
>
> The wear is on the vees and it lets the carriage move sideways.
>
> I have some other possibilities that I am considering.
To get .008 runout, the ways would have to deviate from a straightedge
enough to get a feeler gage in the gap. Test for that.
The 'other possibilities' should include misalignment of the spindle
(it isn't
aimed accurately parallel to the ways).
Jim Wilkins
> On Dec 28, 11:48 am, Ignoramus4115 <ignoramus4...@NOSPAM.4115.invalid>
> To get .008 runout, the ways would have to deviate from a straightedge
> enough to get a feeler gage in the gap. Test for that.
>
> The 'other possibilities' should include misalignment of the spindle
> (it isn't
> aimed accurately parallel to the ways).
You did support the test bar with the tailstock, right???
jsw