On 2010-06-26, Searcher7 wrote:
On Jun 19, 6:55*pm, Jim Wilkins wrote:
[ ... ]
And I assume deflection is why steady rests were made.
It is, but they can't occupy the same space as the carriage. Follower
rests don't help if the part has shoulders. If you tried to turn a 6"
length of 1/4" aluminum without the tailstock it would just climb up
onto the lathe bit.
Of course. (But I don't know what you mean by shoulders).
Where you are turning some cylindrical work and you have two
diameters. That towards the chuck is say 1" diameter, and you are
turning the end down to perhaps 1/2" diameter. Given the power (or lack
thereof) of the Mini-Lathe, you can't make that reduction in a single
pass. Follower rests (which Jim specifically mentioned) ride behind and
above the workpiece and travel with the carriage. Usually, the follower
leads the cutting tool, so on the second (and subsequent) pass(es), the
follower would hit the increase in diameter (the shoulder) and
(probably) cause things to break. Sometimes, it is possible to set up
the follower to trail right behind the tool, so you don't have this
particular problem -- unless you have another shoulder to the right of
the area where you are turning.
Yes. My determination is that with my lathe 9/16" would be the maximum
diameter I could pass through the spindle using 3C collets, because
that is the largest diameter these collets are made for.
Higher than that would require a 5C collet chuck for the 5C collets.
Not if you needed to turn some 3/4" thin walled brass tubing, or thin
a washer, or remove the part to test a fit and then replace it to cut
some more, or turn it around to machine the other end, or file it
without risking precious body parts, or face a batch of pieces to the
same length. An MT3 collet would be fine for all those.
But Isn't MT3 a "tool holding" collet?
Yes. That does not mean that it can't be used for certain
limited work-holding purposes. It won't handle through-the-spindle
workpieces, which is why it is not a work-holding collet.
[ ... ]
MT3 collets use a drawbar, so they are not an option.
Darren Harris
Ask yourself why they are used on rotary tables. An MT2 collet holds
the centering rod hehttp://picasaweb.google.com/KB1DAL/H...10360947850418
But wouldn't an MT2 dead center be better?
Actually -- no. The collet is holding a cylindrical piece onto
which the workpiece slides to hold it centered prior to bolting it down
to the rotary table. It looks as though there were some extra holes
drilled and tapped in the table to improve the clamping of this
particular workpiece.
On the lathe you could do the same to center a gear blank on a
faceplate, I did (with 5C) to turn the OD of that piece. A chuck and
faceplate won't fit at the same time, but you can use a collet with
either, like to hold a depth stop for a chuck.
I'd think to use my MT2 dead center here also.
Actually -- mostly no! The dead center has a conical point. It
sticks out of the spindle by a fixed amount. Where this stops a
workpiece is going to be dependent on whether it has a center hole, and
if so, how deep it is, or how large in diameter.
With the collet, you can put in a piece of stock a little too
long and face the end to provide the proper stop depth.
And I'd have to make
sure that I get a chuck or a face plate with large enough center
bores.
Of course.
Hmm ... I wonder whether my 5C collet adaptor which has a flange
to engage the spindle protector) will fit though my chuck body. (L-00
spindle nose, FWIW. :-)
This may work better on a Hardinge, which accepts the collet
without an adaptor.
Enjoy,
DoN.
--
Email: | 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 ---