Lead screw nut material

[Paul BarterParticipant @paulbarter66156]

Hello all,

Two questions really, the cross slide on my Hobson H7 lathe, a seeming Myford clone,has 5 thou free play.(gib screw released a tad and hand pressure front to back There is no slack in the fixing, I have fitted a needle roller thrust washer courtesy of Arceurotrade, all the endfloat is between the nut and the screw. Is this acceptable? If not I would like to make a new nut as the threads on the screw look fine. and a new leadscrew is probably unobtainable, the Myford version looks similar but is very dear.I hope to cut the thread with a 3/8 Acme tap ,but what material?is brass adequate and if so any particular grade, or should I bite the bullet and use phosphor bronze. Thanks for any suggestions.

[Paul BarterParticipant @paulbarter66156]

[Thor 🇳🇴Participant @thor]

Hi Paul,

Bronze would be a better material than brass for a leadscrew nut, and should last longer. You may want to try to make an acetal leadscrew nut first, see this Link.

Thor

[Anonymous]

Five thou play? I wouldn't even dream of wasting time making a new nut; I'd be getting on making parts!

Andrew

[Paul BarterParticipant @paulbarter66156]

Hi Thor Hi Andrew

Thanks for the clarification, I 'm a chippy by trade and all this talk of thous made me nervous, wood lathes are more forgiving ! Still getting used to these new tolerances.Thanks again

best regards Paul

[Ady1Participant @ady1]

I put a T6 aluminium one into my Drummond M lathe a couple of years ago and she's been fine so far, I also used T6 for replacing the small cog on my backgear

It's quite easy to machine but seems to have tremendous wear and stress resistance, the backgear cog in particular has had some very heavy usage

[Ron FowlerParticipant @ronfowler82506]

Hi Folks,

I know this is an old thread but I've just discovered the lathe I've had for around twenty years is a Hobson H7 (bought it off a friend intending to learn to really use it, but work got in the way. Now retired so dusting it off.)

It was in the Saffron Walden High school for, I reckon, around twenty five years and there's quite a bit of play on the bits that move.

I thought I'd try a new lead screw nut for starters, though I suspect it might want a new lead screw as the first six inches in front of the chuck are, I'm pretty sure, well worn.

So, I'm wondering if a Myford nut will fit – maybe even a Myford lead screw?

Any help greatly appreciated!

Ron

[HopperParticipant @hopper]

Myford leadscrew is 8tpi Acme, from memory 5/8" diameter. You may be able to cut your old leadscrew at the beginning of the threaded portion, turn it around so the worn bit is down near the tailstock and then join the bits up again, using a dowel and pins to hold it together.

[Ron FowlerParticipant @ronfowler82506]

Hi Hopper,

Many thanks! Actually, after posting I went and had a closer look (please remember I'm a real newbie at lathes). Seems it's 8tpi 3/4", but the best of it is I was finding 'play' in the wrong place. Leaving it turned off and putting the lead screw nut 'in gear' revealed that, if there's any play there, it ain't much. However, there is play in the lead screw itself – looks like there's a double nut on the end which I assume is used to adjust the tightness of the lead screw over its length – I'll have another look when it's cool enough to stand in the garage!

[Author]

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