Make new crossslide feed screw

[Andrew EvansParticipant @andrewevans67134]

Hello – I am thinking of making a new feed screw for my Denford Viceroy 280 and fitting angular contact bearings and a new handle. The screw has a gear that drives the power cross feed.

My plan is to buy a 12 mm diameter lead screw rod from RS or similar (seems to be about £13 per m and available either in SS or carbon steel) and a new off the shelf gear if I can find one (or cut the existing gear from the existing screw). Cut the rod to length, machine it, fit the gear by pinning it and loctiting it.

Ideally I want a new feed nut as well. Matching bronze nuts (for the rod) costs about £30 but they all seem to have the mounting parallel to the thread whereas I need the mounting to be perpendicular to the cross slide (if that makes sense).

Has anyone got any experience with fabricating a feed screw like this or any ideas?

Any advice is appreciated. Andy

[Andrew EvansParticipant @andrewevans67134]

For Denford Viceroy 280

[Pete RimmerParticipant @peterimmer30576]

The standard screw is either 1/2" OD x 10tpi or 2.5 mm pitch modified square section. There is absolutely no compulsion for you to follow that odd-ball convention though so a 12mm x 2.5 pitch is a good compromise.

[duncan webster 1Participant @duncanwebster1]

Loctite on its own will be plenty strong enough, drilling diametral through the shaft weakens it. I once blew up (literally) a 1 te hydraulic jack trying to shift some 5"g wheels which had been loctited on

Edited By duncan webster on 02/05/2019 14:12:25

[Clive FosterParticipant @clivefoster55965]

I've done the fit new threads to existing geared shaft thing about three times now on Boxford / SouthBend cross slides. I silver soldered spigots about 1" long into the drilled out gear. Worked well then but now I'd follow Duncan and use high strength Loctite. In one case I used just the gear fitting a new thread one side and new handle / dial carrier the other. (Boxford cross slide on SouthBend lathe apron, gears aren't the same.)

Don't forget thread hand. I think you will need left hand. Affordable options all seem to be right hand.

Hafta fabricate your own mount or make the whole nut unit yourself. I'd be inclined to try the heat-up and mould delrin around the rod method myself. Need to make a carrier but screwcutting really good small threads isn't walk in the park.

Clive

[Howard LewisParticipant @howardlewis46836]

Was about to say that the thread may be a Left Hand, for a Leadscrew, but beaten to the punch!

Being small demand, due to being "non standard", a Left Hand Thread may well be more costly!

Most Leadscrews seem to be square or Acme thread form, rather than conventional V form, presumably for strength and increased contact area. A V form thread will require a new nut, or half nuts, as well.

Could you adapt an existing item, such as for a Myford 7 Series, if you want 8 tpi, or from a Far Eastern machine if you want 3mm pitch?

Howard

[David George 1Participant @davidgeorge1]

Hi Andrew you could screw cut a new nut your self it is only screwcutting internally but with a different shaped cutter i just made a new nut for a adjustable spanner i used a boring bar with a cutter square to the bore an ground to correct width. Why not try a piece of steel before cutting the real one. As for the thread being in the side of the nut just hold it in a 4 jaw chuck.

 

 

Have a go you have nothing to lose.

David

Edited By David George 1 on 02/05/2019 16:48:23

[Pete RimmerParticipant @peterimmer30576]

They are certainly a LH thread. The originals are 'modified square section' Which just means 5 degree flank angle so much more 'square' than ACME or Trapezoidal threads.

[Andrew EvansParticipant @andrewevans67134]

Thanks all for your advice

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