The Shop > Tools

All squared away.

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DavidA:
Everyone seems to have a version of the same idea.

Pete,

..I'd then check that the bar was straight by setting the dial gauge at the end of the bar furthest from the headstock and rotating the chuck by hand. ...

This would not necessarily show the bar was true. You can have a situation where the headstock spindle was absolutely spot on (I should be so lucky ) but any error in the chuck or the chuck back plate would give you the end of the bar rotating around a (small) circle.
You would still need to do the 'rotate and half the error' operation at both ends to find out if the bar or the chuck was causing the difference.

Thanks all for the advice.

Dave

Still pursuing the fabled micron run- out.

Fergus OMore:
Not me :doh: Three or 4 jaw chuck with the longest piece that will swing in the gap. Same as a faceplate.
Face the extreme outer edges and clock . If the up and down worries, put a block the saddle and fit the top slide at 90 degrees. Do the same with the clock or even a bit of fag paper!
It's about the 6th Proposition of Euclid- if I recall.

It's amazing what can be done with a bit of metal 'twer that size and a bit of spit and fag paper.

Norman

edward:
I have the same problem with my ancient drummond. My chuck has a bit of a wobble so plan to turn a bit of something down and mic it. We shall see.....

RussellT:
I think one of the advantages of these methods is that the bar doesn't need to be straight or parallel.  It does need to be round though.

The averaging method takes away all the errors and looks at the axis of rotation of the spindle.

If the bar is a bit wonky then a big foot on the dial gauge might help to eliminate any error due to movement in the wrong plane.

Russell

Fergus OMore:
Sorry, but it is wrong. If you clock a test bar ( ignoring a wiggly chuck or whatever)  your record a combination of out of truth for the spindle- and the wear of the bed.  This cutting of a test piece is all well and good for a new lathe. It is in Myford's setting up instructions for their setting up 'thing'. I've got a test bar that has a No2 MT shank ground from a worn out reamer- great on my lathe which was slideways ground fairly recently - but bloody awful for the same use before that.

The first thing is to assume that moving the saddle is the first step to a quick way to a Moonbeam from a Lesser Lunacy.

Probably the best way is to get the two classic books out. One is Connolly and the other is Schlesinger.  They are the 'modern' editions of Euclid.

And if you have done all this, you still have to do something else- and that is compensate for the deflection of a lathe tool.

Regards

Norman

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