Lead Screw

This topic has 13 replies, 8 voices, and was last updated 24 April 2014 at 11:20 by Russ B.

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23 April 2014 at 17:01 #23267
Alan .204
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@alan-204
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23 April 2014 at 17:01 #150555
Alan .204
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@alan-204
Hi chaps need some help with this one, came home from work and went into the shop to have a play as you do, started on the mill and with in a minute or so lost the table drive after a bit of investigation it became apparent the bronze socket the lead screw runs through had chucked out all of its threads, have removed the part and put a thread gauge on it and its 29 degree's by 10TPI question is what size should the bore be, have ordered a bit of Phosphor bronze from Noggin End Metals should be here by Friday, have done something similar before but can't remember how I worked it out, any help would be useful with working it out.

Al.
23 April 2014 at 17:52 #150557
Nobby
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@nobby
HI Al

It depends on the outside diameter of the lead screw you have the TPI & thread form
Nobby
23 April 2014 at 18:32 #150562
Alan .204
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@alan-204
Hi Nobby it's an Acme thread 29 degrees 10TPI the out side diameter if the lead screw is 0.624 thou, I've just been looking how to work it out but found nothing so far.

Al.
23 April 2014 at 19:00 #150564
Saxalby
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@saxalby
Alan,

This little chart may help –

http://www.unionmillwright.com/2884.pdf

Regards Barry
23 April 2014 at 19:32 #150567
_Paul_
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@_paul_
An alternative might be a home made Acetal nut if you have the space for it, Evanut
23 April 2014 at 22:27 #150582
Alan .204
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@alan-204
Been looking around at different sites and this is the ID I've come up with 0.5270 what do you think chaps.

Al.
23 April 2014 at 22:40 #150583
Keith Long
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@keithlong89920
Al

Perhaps I'm missing something, but you have the lead screw why not just measure it and make sure. The table I've got gives 60 thou as the depth of thread for a 10tpi acme which from your od of 0.624 would give you 0.504 as the core diameter rather than the 0.527 that you ask about. It's possible that it isn't a "standard" acme thread as I believe that a 0.625 od "standard" acme would be 8 tpi not 10 – that is certainly what Tracy tools list for a 5/8 acme tap either rh or lh.
23 April 2014 at 22:48 #150585
Alan .204
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@alan-204
Hi Keith the lead screw is of my Centec 2B mill its definitely 10TPI as I have an Acme thread gauge and the 10 blade fits perfectly, when you say just measure it I can only measure the OD of the lead screw as I have nothing to measure the thread depth, I think that's what you mean.

Al.
23 April 2014 at 23:03 #150587
Alan .204
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@alan-204
I got the ifo from Crank.com it's a link Jason B gave me on an older post.

Al.
23 April 2014 at 23:04 #150588
Alan .204
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@alan-204
I got the ifo from Crank.com it's a link Jason B gave me on an older post.

Al.
23 April 2014 at 23:24 #150590
John Stevenson 1
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@johnstevenson1
Depends of the fit of the thread.

0.625 x 10 at 2G fit has a core of 0.4844

0.625 x 10 at 3G fit has a core of 0.4954

0.625 x 10 at 4G fit has a core of 0.4981
24 April 2014 at 08:39 #150595
Michael Gilligan
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@michaelgilligan61133
Posted by Alan .204 on 23/04/2014 18:32:38:

I've just been looking how to work it out but found nothing so far.

Al.

.

Alan,

This is probably of academic interest only

… it's orders of magnitude beyond my machining ability !!

… but [*] I think it's worth posting for reference.

MichaelG.

[*] given that this discussion has already run from Taps, through moulded Acetal, to core diameters quoted in tenths of a thou.
24 April 2014 at 11:20 #150600
Russ B
Participant
@russb
my metallurgy isn't what it should be, but what affect do you think slowly heating to around 175-200° (270+ if you use nylon) and slowly cooling will have on the mechanical properties and accuracy of that screw?

I know it's not much heat we certainly wont be annealing anything, but I'm thinking there could be a potential for stress relief or movement of some sort – not sure.
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