Dore – Westbury Mark 2 milling machine

[Patrick cubbonParticipant @patrickcubbon94549]

Concern is heavy thread wear of these two components. Any rectification suggestions. For example bore out threading, Loctite in a brass sleeve drilled to 1/2 inch acme tapping size then thread with a tap available from Tracy tools at a cost of £30. Have drawn a blank on the internet!

Thanks in advance for any response, Patrick Cubbon.

[Patrick cubbonParticipant @patrickcubbon94549]

table and cross slide 1/2 inch acme nut castings.

[John HaineParticipant @johnhaine32865]

Moglice?

People have had success casting delrin (I think) around the screw but I can't remember where I saw the technique described.

[Bob Brown 1Participant @bobbrown1]

Patrick,

What do you call heavy wear?

There will be some play in the dials, and do not forget if yours is like mine then the clearance on the dials is adjustable and thus some of the end float can be adjusted.

Bob

[Roderick JenkinsParticipant @roderickjenkins93242]

Posted by John Haine on 29/05/2015 15:53:57:

People have had success casting delrin (I think) around the screw but I can't remember where I saw the technique described.

Here?

I'd saved this for reference in my bookmarks – I've got a Mk I Flexispeed that needs a lead screw and nut – sometime

Rod

Edited By Roderick Jenkins on 29/05/2015 16:21:07

[Capstan SpeakingParticipant @capstanspeaking95294]

Posted by Patrick cubbon on 29/05/2015 14:21:34:

Concern is heavy thread wear of these two components. Any rectification suggestions. For example bore out threading, Loctite in a brass sleeve drilled to 1/2 inch acme tapping size then thread with a tap available from Tracy tools at a cost of £30. Have drawn a blank on the internet!

Thanks in advance for any response, Patrick Cubbon.

Tapping Acme and square threads is tricky and takes a lot of torque even in brass. It would be better to tap it before fitting so you aren't relying on the retaining compound to drive it. Then pin it in.

I'm not you but I'd screwcut it on a lathe.

[AjohnwParticipant @ajohnw51620]

I think it would be worth asking what heavy wear is on the lead screws and if the dials move axially as well ?

My Mk1 had around 0.015in play which I would say isn't bad with no axial movement of the dials at all. I doubt if it was much better than that from "new".

ACME taps should come in 3's just like ordinary taps except they also step up in size. Even then they aren't the easiest of things to cut threads with. I suppose some might be extremely long to achieve the same thing. I'd be very careful if i found I needed to buy one as it might turn out to be unusable.

Personally I wouldn't dream of using delrin. I'd rip into shreds in no time as I set the slides rather tightly. What I should do but haven't is remove the lead screws and set the gib strips up by pushing by hand. Tightening until I feel some resistance.

I too would screw cut replacement nuts if needed in bronze. It might be possible to use a tap if a slightly over deep square thread is cut first. It might be possible to sort out some cnc lead screws and nuts as an alternative.

John

–

[RobboParticipant @robbo]

For a replacement feed nut, try Kingston Engineering in Hull.. Save yourself a lot of grief using an Acme tap!

http://www.kingston-engineering.co.uk or tel 01482 325676

Assume your screw is 1/2" x 10 tpi Acme.

Try their Data Sheet 3 for "Standard Screw Stock" If I remember correctly.

I had a 1" Acme feed nut from them about 18 months ago, and it was superb quality.

You may of course have to modify it to fit your mounting.

Phil

Edited By Robbo on 29/05/2015 23:58:16

[Ady1Participant @ady1]

My T6 aluminium leadscrew nut and backgear cog are still going strong, it's very easy to machine as well

About 3 years so far with very heavy use at times

Delrin only lasted about 6 weeks and my two original leadscrew nuts a year apiece (Drummond M series)

Edited By Ady1 on 30/05/2015 00:58:55

[julian atkinsParticipant @julianatkins58923]

hi patrick,

very interesting query!

i would also like to replace these parts on my Mark 1 which was acquired 3rd hand many years ago.

does Ivan Law still provide spares?

on mine the screws holding the nuts work loose regularly and the holes for these screws are a sloopy fit. also the front one was fitted the 'wrong way round' reducing table movement.

cheers,

julian

[Author]

Posts