Re: Aligning the tailstock?

DR_G wrote:
Hello again,

Basic question no 537 from me:

I'm about to start my first 'real' machining job. It is basically
drilling out a 120mm long, 12mm o.d. bar to 8mm i.d., and relieving the
ends slightly to take 10mm o.d. ball races. The ball races support a 6mm
dia solid shaft (coaxial with the first) with a 'chuck' at one end and
an internal square drive socket for a flexible drive shaft at the
other. The 'chuck' is really a conical bit at the end of the inner
shaft, drilled and tapped to 1/4-28 UNF 2A to take threaded shank twist
drills. For this inner shaft/chuck I intend to turn down another piece
of solid bar to 6mm o.d., leaving a 12mm diameter by about 50mm long
conical end bit for the chuck (thus making the chuck and outer shaft
the same diameter for neatness). I am going to mill a couple of flats
on the chuck in order to fit a spanner for tightening the drills.

My questions are:

1) Any general advice as to how to go about this?

2) What is the best way of aligning the tailstock with the headstock? I
ask this since turning the inner shaft down from 12mm to 6mm diameter I
intend to do between centres, and this needs to be accurate because it
will have a bearing at each end of it. It may be best to turn the
central portion of the inner shaft down a bit (between the bearing
'lands') in order that I can get the first bearing all the way upto the
'chuck' without forcing it all the way along a tightly fitting
(hopefully!) machined surface.

Material is Austenitic st. st. Ground bar, 12mm o.d. x 300 long
initially, for both shafts.

Cheers,

Garth.


First make sure the bed is straight and the lathe turns parallel with a bar mounted in the chuck alone. Adjust the lathe feet until it does.
Then turn a test piece between centres measuring the diameter near to each end. Adjust tailstock until the diameters are the same.
If you cannot get the two test diameters the same then it is possible the tailstock centre height is not the same as the headstock centre height (either due to an improper re-grind or you don't have the original tailstock. Shim either the tailstock or headstock until the heights are identical.

hth

Bob
.

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