A variable Lead threading attachment. Author Ted McDuffie

[Sub MandrelParticipant @submandrel]

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

[jacques maurelParticipant @jacquesmaurel42310]

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

[Ady1Participant @ady1]

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

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi Ady1 ,

To make this thing work at all the lower pivot on the combining lever has to run on a long swivelling radius arm anchored at the other end to some fixed point .

Could work with a slide instead but either way the geometry is imperfect .

MikeW

Edited By MICHAEL WILLIAMS on 18/06/2013 10:32:37

[jacques maurelParticipant @jacquesmaurel42310]

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

[jacques maurelParticipant @jacquesmaurel42310]

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

[jacques maurelParticipant @jacquesmaurel42310]

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

[Gary WoodingParticipant @garywooding25363]

Posted by Ady1 on 18/06/2013 03:11:03:

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 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.

[Ted ClarkeParticipant @tedclarke82795]

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

[Marcus BowmanParticipant @marcusbowman28936]

Jacques,

I have sent you a PM.

Marcus

[Ady1Participant @ady1]

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?

[Neil LickfoldParticipant @neillickfold44316]

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 ?

[Neil WyattModerator @neilwyatt]

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

[Neil WyattModerator @neilwyatt]

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

[Brian WoodParticipant @brianwood45127]

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

[Neil WyattModerator @neilwyatt]

He wants a paper copy. thanks for the offer.

Neil

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