Acme thread

[dave george 1Participant @davegeorge1]

Anyone around the burnley,lancashire area could knock me up a length of acme threaded bar,the thread im need is either 5/16″ or 3/8″ x 8TPI. im willing to pay for their services
Thanks for looking

[dave george 1Participant @davegeorge1]

[Neil WyattModerator @neilwyatt]

8 tpi is pretty coarse for a 3/8" diameter thread, it might be a bit of a struggle. At 1/16" thread depth plus clearance that only leaves less than 1/4" core diameter. It will probably need to be thread milled, even if you put the clearance on the nut instead of the core diameter.

Can you get away with a finer pitch or greater diameter?

Neil

[not done it yetParticipant @notdoneityet]

Tell us more. Length, length of thread, material, why ACME, etc?

Dies are available for purchase (recommend them for finishing a roughed/part formed turned thread). Square threads are often substituted for ACME threads. Do you need a new nut?

HPC Gears can supply a range of items at reasonable(?) prices.

[dave george 1Participant @davegeorge1]

im after a cross slide feedscrew making,for a new cross slide that im getting made,length of cross

slide is 10",and its looking at a 3/8" x 8tpi thread,got to be acme as that was the old feedscrew was

also i dont need the nut as that is in the carridge/apron where the screw will go thru,

i did try a few places and got quoted stoopid prices, 65 quid,50 quid,160 quid, for a 270mm length (this is going off a myford ml7 long cross slide feedscrew)

[not done it yetParticipant @notdoneityet]

for a new cross slide that im getting made

It would seem to be a sensible suggestion that the maker of your cross slide supplies the screw?

[dave george 1Participant @davegeorge1]

http://www.model-engineer.co.uk/forums/postings.asp?th=119194

I am getting a casting made local,im gonna do the milling of the t slots and dovetails myself

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 02/08/2016 21:22:18:

8 tpi is pretty coarse for a 3/8" diameter thread …

.

Agreed … Which is probably why the suppliers list such leadscrews in 'Stub Acme'

http://www.roton.com/Engineering_Data.aspx?line=Acme

Dave: I suggest you check the dimensions of the original thread carefully, before shopping.

MichaelG.

Edited By Michael Gilligan on 03/08/2016 10:25:22

Edited By Michael Gilligan on 03/08/2016 10:26:42

[Jon GibbsParticipant @jongibbs59756]

Posted by dave george 1 on 02/08/2016 22:44:26:

im after a cross slide feedscrew making,for a new cross slide that im getting made,length of cross

slide is 10",and its looking at a 3/8" x 8tpi thread,got to be acme as that was the old feedscrew was

also i dont need the nut as that is in the carridge/apron where the screw will go thru,

i did try a few places and got quoted stoopid prices, 65 quid,50 quid,160 quid, for a 270mm length (this is going off a myford ml7 long cross slide feedscrew)

Hi David,

Just to be sure that you're aware, an imperial ML7 cross slide feedscrew is 10 TPI (100 thou per revolution) and not 8TPI.

They're clearly no bargain but are available new, direct from Myford here… **LINK**

Jon

[HopperParticipant @hopper]

You probably should shop around for some Acme threaded rod. I am sure there has been discussion on here before and a UK industrial supplier was found to be quite reasonably priced. Can't remember the name though. But a forum search for "acme threaded rod" or something might turn it up.

Just for example, and I presume it's wrong side of the pond for you, but McMaster Carr sells 1ft lenghts for not much over $10. See link

**LINK**

[dave george 1Participant @davegeorge1]

Just an update.. i took the old feed scree to an engineer and he said its 3/8″ x 8tpi square thread and not a acme thread. He said a acme thread has a slight slope from the top to the bottom where as mine is straight

[Michael GilliganParticipant @michaelgilligan61133]

Posted by dave george 1 on 03/08/2016 16:20:44:

He said a acme thread has a slight slope from the top to the bottom where as mine is straight

.

Quite so, Dave

**LINK**

https://goo.gl/images/9drHAr

MichaelG.

[mark costello 1Participant @markcostello1]

Does not make it any easier.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by mark costello 1 on 03/08/2016 18:54:46:

Does not make it any easier.

.

No … But it does save making the wrong thing.

MichaelG.

[dave george 1Participant @davegeorge1]

I got to find someone to make this 😨

[John Stevenson 1Participant @johnstevenson1]

Just a suggestion but why not buy a S/H but decent Myford cross slide screw and nut and adapt it ?

[HopperParticipant @hopper]

You have a lathe. Make one. Lock the cross slide in position and set the topslide at 90 degrees to the lathe axis and use it to feed the cut in. A moving steady will probably be required, but is easy enough to make up too.

[dave george 1Participant @davegeorge1]

Yes i have a lathe but its still in restoration mode not been built back up yet

[duncan webster 1Participant @duncanwebster1]

+1 for Hopper's method. Square thread is easier to screwcut than ACME anyway, the tool tip is only 1/16" wide, so if the lathe will part off it will cut this thread

[Neil WyattModerator @neilwyatt]

On such a small diameter an 8tpi thread will require the tool to be at a roughly 19-20 degree angle to stop it fouling the sides of the thread.

Rather than a parting tool grind a cutter on the end of some round HSS, then rotate it to match the helix angle.

Neil

[John PParticipant @johnp77052]

Neil was right at the start of this thread by suggesting that
this leadscrew would be best milled.

The recently published articles in MEW 241 to 243 show
how easily this is done.

Some editing at the end of the article left out an important
aspect of this operation.
The reasons for the editing are not an issue as i could
probably understand why this may have been done ,the
missing text is as follows.

"when cutting the second of these screws i was not even in the workshop ,i
was in my elderly neighbours (older than me) garden trimming up some
bushes,i doubt that there are many that can claim to have made an acme
screw and done some gardening at the same time ".

Of the five leadscrews that were produced and shown in the article i was only
present while the first one was made .
I was shopping in Asda when cutting this 3/8 by 10 tpi seen here in this photo
in the album leadscrew.

Conventional screwcutting these sort of leadscrews is a redundant operation and
a complete waste of time.
The unit as seen will fit on a Myford 7.

John

[John Stevenson 1Participant @johnstevenson1]

Quote:
The recent published articles show how easily this can be done. End quote

Sorry John but I disagree. OK if you have already spent 3 weeks building the attachment and have all the skills but the OP has stated he doesn’t have a working lathe and from the tone, possibly not the skills either.

TBH I don’t think the OP actually knows what he wants. He stated in his first post he wants a length of 5/16″ or 3/8″, then later says it has to fit a tapped nut in the saddle.
Now it’s a very tall order to get anyone to make a thread to fit a worn nut you don’t have.

No mention of end machining has been mentioned hence my suggestion to use an existing Myford screws and nut and make it fit

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

[Roger HeadParticipant @rogerhead16992]

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

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Roger Head on 06/08/2016 02:43:09:

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.

.

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.

.

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

[Roger HeadParticipant @rogerhead16992]

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 ??? 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

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