Gallery, Projects and General > How do I??

Unwanted taper produced - how do I correct?

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raynerd:
Sorry, another thread!  :hammer: Is there another forum for stupid noob questions - I am cluttering your forums but desperate to ask!

I was turning a 8" piece of acrylic today and I noticed that I am producing an unwanted taper! Wider at the tailstock end and tapering inwards towards the headstock - infact, it was pretty bad.  Compound slide is set at 0 and adjuster left alone, I was using the powerfeed to drive the tool so it should not be producing any taper right?

Can anyone tell me what is wrong with my lathe (clarke cl300m 12x7) and how I can correct this?

Al the best
Chris

John Hill:
I am sure John Bogstandard will be along soon with the complete story but in a nutshell it think it means either the headstock is not parallel with the ways or the tailstock is not set in line with the headstock.

If I understand correctly the tailstock usually has an easy adjustment for the very purpose of turning tapers.  The headstock is another matter but not impossible to correct.

John
aka The Artful Bodger

ja2on:
This may help
http://www.gadgetbuilder.com/Lathe_Align.html

I expect the clarke manual is a bit poor so try this one
http://www.littlemachineshop.com/Info/MiniLatheUsersGuide.pdf
unfortunately it does not cover the tailstock adjustment

bogstandard:
Chris,

There is most probably nothing wrong with your machine.

When you have a bar sticking out of the chuck that is unsupported by a centre in the tailstock, especially if it is a flexible material, what happens is the the bar will bend away from the cutter the further away from the chuck it is, so you will not get the full cut that was applied. As you get closer to the chuck, the bar will become more rigid, so you will get the cut that was applied. So less material is removed the further from the chuck the cut is. Hence your taper.

Anything say over 4 diameters sticking out of the chuck (if 1" diameter, then 4" max unsupported) then really you should be supporting it with a centre in the tailstock. That is only a ballpark figure, for a fairly flexible material, say like acrylic or nylon rod, that figure could be reduced to 2 or 3 diameters. Even then, if the rod is fairly long, it will flex in the centre, so you will get the centre part of the rod with a bulge in it. So then a travelling steady should be used, which supports the rod very close to where it is being cut, and stops it deflecting.

John

John Hill:
Now didnt I say Bogs would be along with the complete story! :med:

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