Acme thread

Edited By John Stevenson on 05/08/2016 10:55:02

Apologies if I've missed it, but so far it seems nobody has mentioned that it will need to be a left-hand thread, for a conventional cross-slide operation. In principle it doesn't make any difference, but spending money to buy tooling/pay-someone-to-make/whatever, and then finding that it operates in reverse, would really tee me right off.

Roger

Edit: I see that it is to fit an existing nut. So a conventional RH thread wouldn't even mate, never mind about it operating with the wrong sense.

Edited By Roger Head on 06/08/2016 03:01:47

.

Roger,

Reading between the lines, I'm pretty sure that the screw is for a Grayson lathe, and that the cross-slide operation is rather like a Myford. [although 8tpi not 10tpi]

Myford uses right hand thread **LINK**

http://www.myford.co.uk/acatalog/C25.-FEEDSCREW-AND-NUT-FOR-LONG-CROSS-SLIDE---IMPERIAL--30-135-194.html

MichaelG.

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Edit: I believe this to be a photo of the existing cross-slide.

http://www.model-engineer.co.uk/albums/member_photo.asp?a=41596&p=684946

Edited By Michael Gilligan on 06/08/2016 06:38:15

Good grief !!! So you 'unwind' the handle to drive the cross-slide in ??? I hate to think of how many screw-ups I would make switching between two lathes with opposite actions. I've had my German-built Ford Focus for 10 years now, and I'm only just beginning to treat the left-side-of-the-steering-column turn indicators instinctively .

Thanks Michael, I learn something new every day.

Roger

No,no,no! It depends on whether the screw drives the carriage (left hand) or whether the screw is attached to the carriage (right hand).

Rod

.

No, Roger ...

The nut is on the saddle, and the screw is in a bearing on the slide ... So it works 'naturally'.

You can sleep at night.

MichaelG.

Edited By Michael Gilligan on 06/08/2016 10:19:14

Ahhh...., ok

Posted by Michael Gilligan on 06/08/2016 06:32:18:

Whew, I was starting to develop a nervous tic just thinking about it.

But I still learned something .

Roger

YOu'd best not think about the Drummond/Myfrod M Type with its carriage traverse handwheel that turns clockwise to move the carriage to the left, opposite of pretty much every other lathe ever made.

And the Winfield.

When you ran one of them even the clocks went backwards.

The ML 4 by Myford was another that went in the 'wrong' direction when the carriage traverse handle was turned, not only that but both the tool slide feed screws were 12 tpi square thread with 100 division indicators. I don't think they even had removable nuts, the female threads were directly into the castings.


​Regards

Brian

Edited By Brian Wood on 07/08/2016 20:12:17

Brian,

I don't know for sure but the Grayson could be like this which means making a screw with no access to the nut is basically a toss up but like a lot of these posts the OP seems to have dropped a few crumbs and disappeared.

John,

I do like the expression of having dropped a few crumbs and vanishing; I often wonder at what those OP's get from the replies and then what they do with the information.

Brian

David,

At the risk of getting my head bitten off, there has been a lot of confusing information about the size and type of the thread you want making and I can't really see anyone leaping forward to make a component for you based on a poorly prepared specification. And trying to make it fit a nut, unseen and at a distance, which is probably worn as well, is frankly unrealistic.

Also, why does the work have to be conducted locally to you? Items can be posted.

To cancel your account and close contact only serves to indicate a lack of understanding of what you ask for, you can't force and bully people into a response by such actions.

Brian

Wow. Just wow.

My suggestion to make one yourself came after lengthy discussion but no offers to make one for you because it seemed unclear exactly what thread was required and that there was no nut to fit it to. I made the assumption that as someone restoring an old lathe and undertaking to get a new cross-slide cast and machine it up to fit, making a leadscrew would be well within your repertoire if a little innovation was used. No intent to put you down at all.

In more general terms on this and other forums the question of identifying an internal thread has come up, sometimes Whitworth/UNC being part of the problem, sometimes left/right, sometimes square/Acme, sometimes metric/imperial. So I wonder if anyone has an idiotproof suggestion of how to make a casting of the hole that could then provide a more accessible male version for measurement.

One thought is the hot water temp mouldable plastic granules, or HDPE from milk bottles at a rather higher temp.(175C)

My solution to getting an impression is to scrounge some expired dental impression material, I got a pot of two part material some years ago. The stuff does have a shelf life and I imagine it gets dumped after the due date


​Mixing is in two equal lumps, one of white, one of blue and knead them together thoroughly before shoving it into the aperture, Setting is within minutes after which you peel it away and hey presto,. It will continue to air harden if left.

The impression is sharp and accurate, it has to be for dental mechanics to make plates that will fit correctly.

Brian

Hello John,

​Any time you are up my way, but you must accept that they will be flexible and in a rather fetching shade of pale blue.

They might be good to mumble through soup, but not much else. I imagine the taste of silicone might get rather tedious long term as well.

Brian

Edited By Brian Wood on 09/08/2016 17:26:17