A variable Lead threading attachment. Author Ted McDuffie

Will it do metric threads on an imperial lathe? Will the dial indicator work?

Edited By Ady1 on 16/06/2013 02:33:47

Jaques, Thanks for the dual language titles on your video. I am learning some new French words.

I somehow missed the ME article in 2006 so am glad this came up. It looks very useful for old lathes where most of the change wheels have gone missing and there never were metric combinations anyway. The error shouldn't matter since I find most threads are at most only 2 nuts long.

Hi Mike,

i was musing on whether or not the errors intoruced by using imperfect gear ratios are significant enough to warrant using such a device for fasteners and otehr threads that just need to work, rather than be highly accurate (as in a micrometer stop, leadscrew or similar).

Neil

The anwer to the 2 questions of Ady 1 is yes.

Answer to Michael Williams: the drawing 1 is just here to explain the principle.

J Maurel

I had a feeling about this gadget and ran it through some animation software I have

The problem is that the parallelogram describes an arc as it moves... but the slide won't let it do that and forces the cutting tool part of the unit to move in a parallel fashion... so the geometry either jams up or something has to give(break)

The only solution I can see is where the little arm bolts to the big arm, you need a slot, not a hole, for that bolt as the geometry alters, and this may mess up the thread

It's a bit like a shaper drive, there's a slight arc as the drive powers the shaper head and they use a slot, not a hole, at the top of the drive

Anyway, if anyone ever builds one of these things for real... then we'll find out

I've made a sofware simulation using Solidworks and the kinematics application motionworks, with the example already given (20 tpi from 1mm standard lead) the error for 90 mm thread length machined is about 0.004mm, less than the lead screw tolerance!

J Maurel

I've made a short video showing the attachment at work: cutting a 3/4" BSP thread (14TPI) on a metric lathe (actual lead 1.5mm).

**LINK**

J Maurel

Here is a link to my website, I've gathered some informations on the attachment and there is a drawing and a photo showing a threading machine from the eighteenth century using the same principle: **LINK**

J Maurel

I think you're wrong, because it's not a parallelogram at all. The schematic diagram is not particularly good, and is certainly not clear.

Point D is attached to the saddle via the topslide, and item 2, which holds the tool, slides across it as the lever AC rotates about point C. The link DB (item 4) is is free to rotate at both ends, so, although the vertical distance between point D and item 2 remains constant, the vertical distance between points A and B reduces as the lever rotates about point B, as does the vertical distance between points C and A.

I have built a version of McDuffie's inventrion and checked its accuracy. My version is described in my article for the web journal Modern Microscopy: **LINK**

Ted

Jacques,

I have sent you a PM.

Marcus

I'm still not convinced about this

Anyone got it to the stage where you slap it on the lathe and run a thread out yet?

Jacques,

So if the sliding tool holder was set on angle, would it then be possible to turn tapered threads?

Have you got pictures showing your setup without the chip cover ?

Has anyone got a spare copy of the issue of MEW with this in?

Ted would dearly like to have a copy, but there are no back issues left.

Please pm me or email if you can help.

Thanks

Neil

My apologies, and thanks to those who have already replied. I should make it clear it is Ted Clarke who needs a copy of the MEW with his article, "Adjustable Threading Feed Attachment for the Lathe" it is Issue 204, not Ted McDuffie who wrote the earlier article.

I have asked before, but if anyone does have a paper copy, please do let me know.

Thanks

Neil

Hello Neil,

Does he want the whole magazine or just a copy of his article?.

I don't want to part with my copy, but I am quite willingly to scan and email from it.

Regards Brian

He wants a paper copy. thanks for the offer.

Neil