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PeteF
07-21-2011, 11:54 PM
Hey guys I'm looking for a LH nominal 1/2" ACME tap, but metric thread of 2mm. It's for a X axis leadscrew on a metric machine. Does anyone know if such a tap exists and if so where I can buy one? Please don't say McMaster as they won't sell to Australia, we being such a security risk and all :rolleyes:

Thanks.

Pete

Davo J
07-22-2011, 12:09 AM
RDG have them for a reasonable price
http://www.rdgtools.co.uk/acatalog/ACME_TAPS__LEFT_HAND_.html

I have given that link to a few members and they have been happy with the quality of the taps for things like new cross slide nuts.

Dave

PeteF
07-22-2011, 12:28 AM
Ok thanks, however I don't see any there with 2 mm pitch, do you have another link to them?

Davo J
07-22-2011, 01:02 AM
Here is the link, I missed the 2mm pitch bit, but it doesn't look like they have metric.
http://www.rdgtools.co.uk/acatalog/ACME_TAPS.html

You could use a piece of metric acme rod to make a tap.

Dave

PeteF
07-22-2011, 01:12 AM
You could use a piece of metric acme rod to make a tap.

Dave

Yes, that's one option, if I can find some LH 1/2" x 2.0 mm pitch acme leadscrew ;)

I suspect this machine was built at a time when Australia had converted to metric, yet Hercus (the manufacturer, it's my type 0 Dave) was still building their imperial machines but "metricized" ... hmm is that a word :p

I'm guessing if I want this in bronze I'm going to have to single point it, a task I'm definitely NOT looking forward to, although it's certainly better than the square thread I initially thought it was. It's fine enough to be difficult to see really well, at least while still on the machine. However before getting too carried away with my assumptions I thought I'd throw the question out on the board. It's not something I deal with every day and who knows, maybe somebody will pop up and say, "Ohhh a half by 2 mm, sure I've got a draw full of them" ... or maybe not :D

Thanks for trying anyway.

Pete

Davo J
07-22-2011, 01:16 AM
This may help out a bit with making one.
http://www.rittercnc.com/modelengineering/Hardening-21766-.htm

Also someone on the WWforum posted about a old guy down in Melbourne (I think it was) that ran a treading shop and was closing up, he might still be going.

Dave

Edit
Found it
The number was for "M.P. Sinclair Pty. Ltd." at 12 Lens Street, North Coburg 3058 - phone 03 9354 2588, Fax: 9354 6760

Davo J
07-22-2011, 01:23 AM
Yes, that's one option, if I can find some LH 1/2" x 2.0 mm pitch acme leadscrew ;)
Thanks for trying anyway.

Pete

You could cut some on your lathe to use for it.

That link above to the SS guy, he was offered either a square of round bronze nut.

Dave

PeteF
07-22-2011, 03:00 AM
Dave, my idea is to thread a piece of Phosphor Bronze, I've possibly even got some suitable here already if I scratched around hard enough. Once I'm happy with the fit on the screw I'll turn it to size, bore out the old casting and press the new one in with loctite to secure it. It's not real urgent, it would just take out a bit of the X backlash, however it's not too bad to be honest. Bob very kindly gave me a new nut for the Y axis, and the knee is perfectly tight. If I got the X spot on it would be as good as the machine could be.

Pete

Circlip
07-22-2011, 03:36 AM
Forgotten the melted/molded acetal version???

Regards Ian.

Greg Q
07-22-2011, 04:19 AM
The place in Melbourne ain't all it's cracked up to be. Went to have a look at their wares last month. Its a machine shop straight out of 1939. Their acme stock looked like it had been chewed by rats, and they wanted some fancy money for it too. Nice guy, but living in the past.

One thing I did learn from him is that all "acme" stock specified in metric is in fact trapezoidal thread with a 30 flank. I haven't had time or reason to verify that factoid.

form_change
07-22-2011, 04:37 AM
Yes, for some annoying reason metric ACME is 30 degrees, while imperial is 29 degrees.
I've single pointed a bit of phosphor bronze - it's not too bad if you have sharp tools.

Michael

John Stevenson
07-22-2011, 05:12 AM
I bought all the feedscrews taps at the Myford sale.
Just been and checked and I do have a 1/2" x 2 but only in RH.
They are clearly marked acme so I reckon that because the machine tool makers were using acme on all other sizes these would be done acme as well even though they are a hybrid.

All these taps I bought are clearly marked Dormer but I reckon that whey would have been special order as opposed to off the shelf.

PeteF
07-22-2011, 05:47 AM
Forgotten the melted/molded acetal version???

Regards Ian.

No hadn't forgotten about it, just prefer to do the job in PB. If I was desperate I'd use plastic, but as I said it's not like it's urgent.

Greg, oh yes, you're quite right!! I had forgotten that.

John, thanks for the heads-up, I'll do some more searching.

Pete

.RC.
07-22-2011, 06:25 PM
So the question is.... Is the 1/2 2mm thread ACME or trapezoidal?

TexasTurnado
07-22-2011, 06:41 PM
I'm guessing if I want this in bronze I'm going to have to single point it, a task I'm definitely NOT looking forward to, although it's certainly better than the square thread I initially thought it was. It's fine enough to be difficult to see really well, at least while still on the machine. However before getting too carried away with my assumptions I thought I'd throw the question out on the board. It's not something I deal with every day and who knows, maybe somebody will pop up and say, "Ohhh a half by 2 mm, sure I've got a draw full of them" ... or maybe not :D

Thanks for trying anyway.

Pete

I ground a bar and single pointed a 1/2 x 10LH bronze nut for my Atlas without problems - you should not have much trouble doing it at 2mm pitch.....

Bob Fisher
07-22-2011, 08:44 PM
Try Victor machine in New York. Don't know if they ship down under though. It really is not that difficult to single point,once you manage to grind a tooth form that is acceptable, you can easily make several for spares, AND you still have the cutter for another time. I did a 7/16 x 10 LH for my Logan, 1/2 in gives you a little room. I made two from cast iron and two from bronze. Bob Fisher.

TexasTurnado
07-22-2011, 10:16 PM
Try Victor machine in New York. Don't know if they ship down under though. It really is not that difficult to single point,once you manage to grind a tooth form that is acceptable, you can easily make several for spares, AND you still have the cutter for another time. I did a 7/16 x 10 LH for my Logan, 1/2 in gives you a little room. I made two from cast iron and two from bronze. Bob Fisher.

I like the single point method better because you can size the nut to exactly fit your screw, with min backlash. Of course, if your screw is worn, that can be a problem - but in that case I use precision threaded Acme screw stock to make a new screw, and then fit the nut to that....