Pallas mill adjustments

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Pallas mill adjustments

This topic has 6 replies, 4 voices, and was last updated 12 December 2016 at 22:33 by Peter Lamb 4.

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4 December 2016 at 16:48 #269848
Peter Lamb 4
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@peterlamb4
I am hoping someone may be able to advise me on how to adjust the main spindle of my mill. It is a Pallas horizontal machine that I think is 1950's or 60's vintage. It has no plate with exact details so I am working off information from the lathes.co.uk web site (the best I have found so far). There are some photos in an album I have created that will give exterior views – attached here. There is some run-out if I put a ~ 6" arbour in the bore which is 4MT. I have put a taper reamer down the bore and cleaned out a small high spot so I think what is left needs taking up on what I assume are taper roller bearings. I would like some advice before taking things apart if someone has done similar. Thank you
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4 December 2016 at 16:48 #12829
Peter Lamb 4
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@peterlamb4
4 December 2016 at 20:44 #269909
not done it yet
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@notdoneityet
Adjustment for tapered roller bearings is usually to give zero end float plus a small amount of preload.

That preload may depend on the construction materials (coefficients of linear expansion) and the operational temperature, to avoid any end float during normal operation.

If end float is the cause of the run out, it should be noticeable by deflection by side or vertical thrust on the shaft while measuring.

Horizontal cutters may have a slight run-out during operation, but this usually only means a slightly larger cut on some cutter teeth – to which you may become accustomed. – and is not generally over important in operation.

I'll now go and look at lathes dot co. These old horizontal machines are often overlooked (by vertical options) but have plenty of life in them (from a Centec owner), and are often of better quality than modern chinese 'equivalents'.

Edited By not done it yet on 04/12/2016 21:12:29
4 December 2016 at 21:30 #269913
Neil Wyatt
Moderator
@neilwyatt
Some useful advice here:

http://www.model-engineer.co.uk/forums/postings.asp?th=103092&p=2

Main points:

No shake but not too tight – zero to minimal preload is normal for taper rollers (less than with angular contact bearings).

Don't fill more than 1/4 of the space in the bearing with grease, any more and it can damage or overheat the bearing, especially if it has nowhere to go. Packed bearings are for keeping salty water out of car wheels, not lathes!

Perfectly set they will run warm, but not hot.

If you cant keep your hand on the bearings, (too hot) , they are too tight.

An IR non-contact thermometer is a great help.
12 December 2016 at 09:13 #271318
Peter Lamb 4
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@peterlamb4
Thank you both for the advice and guidance. I haven't noticed any float on when checking with the stub shaft but will try again. This may well be my Christmas holiday job! I will check temperatures as suggested and can probably borrow an IR unit from work.
12 December 2016 at 11:30 #271344
daveb
Participant
@daveb17630
Nice old machine! It's worth checking that the arbor fits the Morse taper, the shoulder can prevent the taper from fully entering the socket. I suppose this could happen if the socket as been cleaned out with a Morse taper reamer. I relieved the shoulder and the taper now needs a firm tap to release it.

Dave
12 December 2016 at 22:33 #271468
Peter Lamb 4
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@peterlamb4
Thanks Dave. I think the arbours are clear of the shoulder but will check again – they do need a tap to free up so I think are home on the taper Ok. It has taken a slight beating over the years and I did need to clean up the "nose" of the spindle when I got it as the vertical head drive shaft had come lose on its draw-bar and run round out of the socket – the shaft was worst off but cleaned up ok.
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