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old mart
06-28-2015, 04:45 PM
I have bodged up the crosslide leadscrew and nut on the museum's old SMART & BROWN model A lathe but would really like to get hold of 1/2"X 8 acme threaded steel and bronze nut. This size is unavailable in the UK and while it is stocked in the US, getting a tiny order sent is not hopeful. I have even considered 5/8" X 8 which could be made to fit, but this is also difficult. In the UK metric equivalents are everywhere but no imperial.

Optics Curmudgeon
06-28-2015, 04:56 PM
First, check to make sure it's not left hand. Second, consider making a replacement from stressproof. It's not hard to do, and you can make a complete lead screw without splicing the new piece in (as I imagine you are planning to do). The nut can be made to match.

John Stevenson
06-28-2015, 04:59 PM
Kingston Engineering in the UK do 1/2" x 10 and 5/8" x 8 in acme.

http://www.kingston-engineering.co.uk/data-sheets.php

EddyCurr
06-28-2015, 05:03 PM
... and while it is stocked in the US, getting a tiny order sent is not hopeful.I readily see individual lengths of [ ... Oops ... ] for leadscrews listed for US$ 11.00 on the auction site.

That's one example, no doubt others exist - maybe with
better freight options.

Perhaps there is a vendor out there that will package
a length together with a suitable nut. Another possibility
is to fabricate a nut using the method Evan wrote about:


Making Acetal leadscrew nuts the easy way (http://bbs.homeshopmachinist.net/threads/43645-Making-Acetal-leadscrew-nuts-the-easy-way) 2010.09

Evanut mounting question (http://bbs.homeshopmachinist.net/threads/60672-Evanut-mounting-question) 2013.09

Edit: the link I removed was for 1/2-10 x 36, not 1/2-8 as requested.

.

old mart
06-28-2015, 05:20 PM
It is indeed a left hand thread, and as for using any plastic, I fear that space limitations would make it difficult to provide a secure mounting. I only require one foot of rod. The lathe is too worn to consider producing the acme thread in house, also the backgear does not work, and I don't want to fix it as a bronze gear in that system has poor teeth. I will get in touch with Kingston Engineering to see if they deal with small orders.

wierdscience
06-28-2015, 06:10 PM
Roton has it as a stock item,but I don't know if they ship internationally.

http://www.roton.com/mating_components.aspx?family=7161422

oldtiffie
06-29-2015, 12:00 AM
That hurdle was discussed and over-come here some time ago.

Get someone in the USA to act as your agent and to buy it on your behalf and then pass the parcel onto you with an account including the original cost plus agent's handling fee and any incidentals plus post and handling.

It could be that the agent can buy it cheaper then the advertised price and that's a "plus" in your favour.

It might seem a bit "steep" but if you need it and that's the only way of getting it, then its that way or no way.