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powertools

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Following on from my Zyliss vice wanted post I now have the 4 that I want however I would like to modify at least 1 to be the same that katellwood has shown in his reply to that post.
Inorder to do this I would need a threaded rod the same thread that is already in the vice but 80cm long.
Am I right in thinking that this is called an acme thread? the dia is 14mm and it has 6 tpi.
Can I buy this in that sort of length and if so were from?
Many thanks in advance.
 

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CHJ

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14 MM does not gell with standard Acme.

5/8" X 8 TPI ACME (15,875 mm dia.)
7/8" X 6 TPI ACME (22,225 mm dia.)
 

powertools

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Thanks for your reply, maybe they used their own thread.
I think that I have come up with an idea of how to do this using the orignal thread but using longer rods and adjusting the position of the fixed head on the longer rods with locking pins and reversing the moving head on the short thread for final adjustment.
 

CHJ

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bosshogg":3936q723 said:
If you re-measure, could it be that it's 9/16" (0.5625) and not 14mm?...bosshogg :)
9/16 is not a 'standard' ACME but would be more like 8-10 TPI if it stayed in step.

I think the metric equivalent 14mm has a pitch of 3mm which is aprox. 8.5 TPI
 

powertools

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Thanks for the help so far, I will remeasure it in the morning and post back.
To be honest I am a bit out of my depth here with this sort of thing but would like to find a rod with this thread.
 

powertools

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Iv'e stripped 1 of these down to make it easier to measure and the dia is 14.10mm or .556" and it is 6tpi.
It would be handy if anyone could point me in the right direction as to thread type and suppilers.
 

Modernist

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powertools":5naljqev said:
Iv'e stripped 1 of these down to make it easier to measure and the dia is 14.10mm or .556" and it is 6tpi.
It would be handy if anyone could point me in the right direction as to thread type and suppilers.
Looks like 9/16" 6 tpi

No idea where to source it I'm afraid. Local machine shop could make it if they are half decent.
 

powertools

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Having spent way too much time on Google learning all there is to know about acme threads I have come to the conclusion that this is not a standard thread form.
My best hope to do this is that katellwood buys his dad a new lathe for Christmas and sell me his vice.
 

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powertools":2wzixl5g said:
Having spent way too much time on Google learning all there is to know about acme threads I have come to the conclusion that this is not a standard thread form.
My best hope to do this is that katellwood buys his dad a new lathe for Christmas and sell me his vice.
Sure it's not trapezoidal? The ISO variant of acme? The size indicates that it's a non- standard acme though, but an angle check is in order. Acme is 29 degrees, trapezoidal is 30. When you have figured it out, find a tame engineer locally, preferably an old school one, which can make you a new one. It's just the same as any other single point threading on a lathe it's just a different cutter.
 

CHJ

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Henning":392dnjv8 said:
When you have figured it out, find a tame engineer locally, preferably an old school one, which can make you a new one. It's just the same as any other single point threading on a lathe it's just a different cutter.
Cost !! A one off made to order to fit the existing nuts, well into 3 figures I'm afraid.
Set-up time, and trial fit to nuts could involve a couple of hours for starters.

Most small shop lathes will not have capability to gear down to 6TPI, **so that rules out 80% of hobby metal turners.
Their lathes are not likely to have the bed length or travelling steadys to work it either.


Best bet would be to 'find' another 'spare' and have them tenoned together end to end to make a longer reach.

** the gearing loads involved in moving a lathe carriage along the bed at that speed in relation to the spindle revs are very high. Most hobby turners attempting this, assuming they have the gearing, would be in the area of having to hand crank the lathe in order to be able to control the stopping point etc.
 

jasonB

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CHJ. ** the gearing loads involved in moving a lathe carriage along the bed at that speed in relation to the spindle revs are very high. Most hobby turners attempting this said:
Its not so much the speed the tool moves at as the load it puts onto the leadscrew, If you can get the gear ratios right then its usual to crank the leadscrew not the spindle and let the leadscrew drive the spindle rather than the more usual way of having teh spindle drive the leadscrew.
 

CHJ

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jasonB":533614kz said:
[.... If you can get the gear ratios right then its usual to crank the leadscrew not the spindle and let the leadscrew drive the spindle rather than the more usual way of having teh spindle drive the leadscrew.
Precisely what I had to do a few days ago for a 1" X 8TPI (unc) repair for someone. Took me all day.
My little 920 struggles a bit with this sort of thing.

Can't do the 6 TPI that my wood lathe spindle uses as I'm an extra 80 tooth gear short, not sure I could be bothered anyway as second user bits are not hard to come by and are an easier option to machine and adapt.
 

powertools

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Thanks for the replies.
Having now become a bit of an expert on acme threads and linear motion I have decided to abandon this project as it could well go wrong and I would have to reopen the Zyliss vice wanted thread.
I realy must stop reading these forums as I have now dug out my unused for 20 years Yankee screwdriver to see if I can make use of it and if I am not very careful I just may rip off the perfectly good plastic handles on my Stanley chisels and spend hours making wooden ones just to end up where I started.
 

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