Acme thread

[Roderick JenkinsParticipant @roderickjenkins93242]

Posted by Roger Head on 06/08/2016 09:58:48:

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

Myford uses right hand thread **LINK**

Good grief !!! So you 'unwind' the handle to drive the cross-slide in ???

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

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Roger Head on 06/08/2016 09:58:48:

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

Myford uses right hand thread **LINK**

Good grief !!! So you 'unwind' the handle to drive the cross-slide in ???

.

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

[Roger HeadParticipant @rogerhead16992]

Ahhh…., ok

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

You can sleep at night.

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

But I still learned something .

Roger

[HopperParticipant @hopper]

Posted by Roger Head on 06/08/2016 12:51:07:

Ahhh…., ok

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

You can sleep at night.

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.

[John Stevenson 1Participant @johnstevenson1]

And the Winfield.

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

[Brian WoodParticipant @brianwood45127]

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

[John Stevenson 1Participant @johnstevenson1]

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.

[Brian WoodParticipant @brianwood45127]

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

[dave george 1Participant @davegeorge1]

Can a mod close this thread please as non of the posts has helped me to find someone to make me a square threaded bar. As for the other posters, ok im not a sh☆t hot engineer like most of these replies,like telling me to make one etc but it doesnt help when you half blind and these negative posts that put you down also this is gonna be my last post on this forum as ive found it quite unfriendly

[dave george 1Participant @davegeorge1]

Also delete my account aswell

[Brian WoodParticipant @brianwood45127]

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

[HopperParticipant @hopper]

Posted by dave george 1 on 08/08/2016 14:16:13:
Can a mod close this thread please as non of the posts has helped me to find someone to make me a square threaded bar. As for the other posters, ok im not a sh☆t hot engineer like most of these replies,like telling me to make one etc but it doesnt help when you half blind and these negative posts that put you down also this is gonna be my last post on this forum as ive found it quite unfriendly

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.

[BazyleParticipant @bazyle]

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)

[Brian WoodParticipant @brianwood45127]

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

[John Stevenson 1Participant @johnstevenson1]

Do you reckon that you can knock me a new set of gnashers up then Brian ?

[Brian WoodParticipant @brianwood45127]

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

[BWParticipant @bw]

Posted by Bazyle on 09/08/2016 13:59:29:

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)

I've read about a metal with a very low melting point ie less than boiling water Somebody will know the stuff I mean. Probably used 50 years ago and outlawed nowadays ?

Bill

[MWParticipant @mw27036]

Posted by Bill Wood 2 on 10/08/2016 00:06:54:

Posted by Bazyle on 09/08/2016 13:59:29:

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)

I've read about a metal with a very low melting point ie less than boiling water Somebody will know the stuff I mean. Probably used 50 years ago and outlawed nowadays ?

Bill

maybe bismuth or cadmium alloy?

Michael W

[John Stevenson 1Participant @johnstevenson1]

Woods metal or Cerrobend

[Brian WoodParticipant @brianwood45127]

Having introduced it in a molten stage to a blind bore with a thread you want to measure, how do you expect to get it out for measurement if you can't unscrew it?

​Plumbers merchants stock it, it is used as a fill material in pipe bending which can be melted out again after the bending. Melting point is about 100 degrees C

Brian

[Anonymous]

I thought Cerrobend had a melting point of around 70ºC?

Andrew

[Brian WoodParticipant @brianwood45127]

Andrew,

I knew it was at hot water temperatures, but how hot I wasn't sure so opted for boiling to be sure. My point about extraction is still valid though.

Brian

[BWParticipant @bw]

Posted by Brian Wood on 10/08/2016 08:27:57:

Having introduced it in a molten stage to a blind bore with a thread you want to measure, how do you expect to get it out for measurement if you can't unscrew it?

​Plumbers merchants stock it, it is used as a fill material in pipe bending which can be melted out again after the bending. Melting point is about 100 degrees C

Brian

Would this work ?

Grease the blind hole with something

Cut / grind a piece of dowel in half to make a D shaped piece of dowel the same diameter as the hole

Insert dowel into blind bore and fill up other half of hole with your molten material.

When cooled pull out the half dowel with pliers and you now have some room to wiggle the newly cast materila loose and you have a "half cast" that you can measure the thread on.

There may be some molten material get behind the dowel but these remnants would surely be fairly weak and broken with a bit of wiggling.

Bill

[John Stevenson 1Participant @johnstevenson1]

Simples

Put a dam on top of the threaded hole, pour the cerrobend into the hole and fill the dam.
Then saw a screwdriver slot in the top and wind out.

The clue is in the bit that says ” Threaded Hole “.

[Brian WoodParticipant @brianwood45127]

I've already given my solution on the previous page, the material was free and it can be used for any kind of impression taking.

I used it to make copies of the church key, a great big Victorian thing with complex wards that would be impossible to separate having poured metal round it; it will also make an archive copy of a magnetic particle indication of a crack if so needed.

I have also screwed bits of soft timber into threaded holes to determine the pitch, not very informative on thread angle if it were needed but a faithful impression will capture that detail too.

Brian

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