Elliott mill

[Ian ReidParticipant @ianreid12250]

<li style=”text-align: left;”>I have an Elliott Victoria juniormil with a very badly worn lead screw and nut on the cross slide. The lead screw is 3/4” dia. 8 tpi. Wear allows the feed handle to move with about 40 thou slack. I cant find replacements. I am wondering if I fitted a DRO I could rely on that rather than the hand wheel, or fit a new metric leadscrew and nut and recalibrate the hand wheel. Anyone done similar and have advice welcome.

[Brian WoodParticipant @brianwood45127]

Ian,

Have you thought about a replacement from one of the suppliers that specialise if feed screws and matching nuts?

Try Halifax Rack and Screw.

Regards

Brian

[Ian ReidParticipant @ianreid12250]

hi Brian, I just looked at their website, I think they could make better than new. Cost would probably be the problem, I have put up with the wear(the other two leadscrews and nuts are not much better) for years. The DRO route would be relatively inexpensive but are there snags using worn out lead screws with accurate indicators?

[Brian WoodParticipant @brianwood45127]

Hello again Ian

Sloppy feed-screws will give less movement than expected. Your DRO route will measure actual travel, irrespective of the indicated value, but you will have all the fitting task to install the scales and readers.

It will be your choice of course on the simpler installation of new feed screws and nuts, but if the cost is prohibitive you do have the alternative, which will of course have its own cost.

Brian

[Ian Reid]

On Ian Reid Said:

The DRO route would be relatively inexpensive but are there snags using worn out lead screws with accurate indicators?

Yes Ian, climb milling is scary otherwise no.

Have you measured the screw thread in the middle and each end to confirm it’s the screw? You may be able to halve the backlash with just buying a length of screw.

HPC also does Acme lead screw stock.

[BazyleParticipant @bazyle]

You know the leadscrew nut is way more complex than simple milling machines incorporating as it does the feed mechanism?
Check the leadscrew mounting for play and the nut mount. Then measure pay in movement with leadscrew at centre and each end to establish both the nut and screw wear.

[Ian ReidParticipant @ianreid12250]

I dont know if the lead screw is a square thread or Acme. Looking at the unworn end  it looks square but in the worn central part almost like a whitworth thread. The “nut” is a simple cast iron bracket, fixed with 4 cap head bolts, threaded to suit the screw, its not powered, and has no play adjustment.  Visually there is more wear in the screw than the nut.

[BazyleParticipant @bazyle]

I was assuming it was like the exploded parts diagram on Lathes.co.uk. So not so bad.

[old martParticipant @oldmart]

8 tpi is closest to 3mm pitch and if you can live with metric or engrave a 118 dial to convert to thousandths, a new leadscrew and nuts would be the easiest way, as long as you have a lathe to finish machine it.

The Smart & Brown model A lathe had a worn out cross slide leadscrew and I saw a new leadscrew with two nuts which was plenty long enough on ebay. Advertised as 1/2 x 8 ACME LH, it turned out to be 3mm pitch and when I contacted the seller, he kindly refunded my money and also said keep it. I ended up fitting it with both nuts in antibacklash configuration and we engraved a 118 dial to replace the original 125 dial. The error per turn is insignificant.

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