ACME thread identification question.

[old martParticipant @oldmart]

Thread rolling is a specialised process, which most firms would sub out to the experts.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by S.D.L. on 14/09/2019 16:52:51:

Halifax Rack and Screw make precision leadscrews, Used to serve the machine tool industry.

I know they will also make Ba$tard sizes as where I work they used to make us a 16mm x metric pitch ACME in stainless steel.

.

Perhaps you could explain then, Steve [please]

Why would anyone choose to specify 16mm x some metric pitch in ACME form rather than Metric Trapezoidal ?

[my brain hurts] … Is it just to make it difficult for customers to second-source spares ?

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by old mart on 14/09/2019 18:58:08:

Thread rolling is a specialised process, which most firms would sub out to the experts.

.

But why would those experts want to roll an ACME thread-form to Metric dimensions.

True ACME is [to the best of my knowledge] exclusively specified in Imperial units.

… If I am wrong; would someone please tell me

MichaelG.

[Pete RimmerParticipant @peterimmer30576]

ACME is standardised in imperial units but the form can be used for metric leads. If you were cutting the thread to a metric lead you'd have to convert the lead to inch pitch then grind the tool nose width appropriately. However, if you were rolling that metric thread you'd have to have a non-standard set of rolls manufactured.

Since the vast majority of the early Boxfords were inch screws I wonder if they had the metric threads cut but the inch ones rolled for cost purposes?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Pete Rimmer on 14/09/2019 20:32:26:

ACME is standardised in imperial units but the form can be used for metric leads. If you were cutting the thread to a metric lead you'd have to convert the lead to inch pitch then grind the tool nose width appropriately. However, if you were rolling that metric thread you'd have to have a non-standard set of rolls manufactured.

Since the vast majority of the early Boxfords were inch screws I wonder if they had the metric threads cut but the inch ones rolled for cost purposes?

.

< my emboldening >

.

That's what I was wondering, Pete

… hence my hope that someone might know for sure how the metric screws were made.

MichaelG.

Edited By Michael Gilligan on 14/09/2019 21:20:37

[Pete RimmerParticipant @peterimmer30576]

I guess you'd need to find an ex-employee from the factory for that, or a drawing.

BTW I had an Denford TDS1 and the cross slide thread on that was clearly cut (or at least finished) with a die. The marks where the die stopped were plain to see.

[S.D.L.Participant @s-d-l]

Posted by Michael Gilligan on 14/09/2019 19:01:53:

Posted by S.D.L. on 14/09/2019 16:52:51:

Halifax Rack and Screw make precision leadscrews, Used to serve the machine tool industry.

I know they will also make Ba$tard sizes as where I work they used to make us a 16mm x metric pitch ACME in stainless steel.

.

Perhaps you could explain then, Steve [please]

Why would anyone choose to specify 16mm x some metric pitch in ACME form rather than Metric Trapezoidal ?

[my brain hurts] … Is it just to make it difficult for customers to second-source spares ?

MichaelG.

I always put it down to one of my predecessors being stupid. I was never able to find out why but my guess was they didn’t know about trapezoidal.

Sometimes things conspire against you I designed a pneumatic cylinder 150mm Diameter with a screw on end, It was supposed to be 150mm x 2mm or something similar, had been told we had got the internal and external tips, but we hadn’t got the Internal so it was done 150mm x 12 TPI Whit. I calculated the dimension for 3 wire on the external thread and we made that fist then did the internal thread to fit.

In most of these cases its ignorance or expedience.

Steve

[S.D.L.Participant @s-d-l]

Posted by Pete Rimmer on 14/09/2019 21:44:44:

I guess you'd need to find an ex-employee from the factory for that, or a drawing.

BTW I had an Denford TDS1 and the cross slide thread on that was clearly cut (or at least finished) with a die. The marks where the die stopped were plain to see.

How are you sure it was a die? Threads cut with an Anjest attachment have a run out like a die as do modern CNC threads no need for an undercut with either.

Steve

[Michael GilliganParticipant @michaelgilligan61133]

"In most of these cases its ignorance or expedience."

… nice summary, Steve.

MichaelG.

Edited By Michael Gilligan on 14/09/2019 22:07:13

[S.D.L.Participant @s-d-l]

Posted by Michael Gilligan on 14/09/2019 19:07:15:

Posted by old mart on 14/09/2019 18:58:08:

Thread rolling is a specialised process, which most firms would sub out to the experts.

.

But why would those experts want to roll an ACME thread-form to Metric dimensions.

True ACME is [to the best of my knowledge] exclusively specified in Imperial units.

… If I am wrong; would someone please tell me

MichaelG.

A lot of leadscrews are cut by thread wirling, The most accurate are ground.

Steve

[Michael GilliganParticipant @michaelgilligan61133]

Posted by S.D.L. on 14/09/2019 22:09:11:

A lot of leadscrews are cut by thread wirling, The most accurate are ground.

.

Yes, Steve : But the Boxford drawing that Pete posted explicitly states 'Plunge Roll'

MichaelG.

[S.D.L.Participant @s-d-l]

Posted by Michael Gilligan on 14/09/2019 22:29:53:

Posted by S.D.L. on 14/09/2019 22:09:11:

A lot of leadscrews are cut by thread wirling, The most accurate are ground.

.

Yes, Steve : But the Boxford drawing that Pete posted explicitly states 'Plunge Roll'

MichaelG.

Yes but that’s for imperial ACME, they may have done the metric by another method?

Steve

[Michael GilliganParticipant @michaelgilligan61133]

Indeed, Steve

That's why I've been banging-on about wanting to know how it was made.

It's of no relevance to me personally … just an interesting puzzle.

MichaelG.

[Pete RimmerParticipant @peterimmer30576]

Posted by S.D.L. on 14/09/2019 22:04:13:

Posted by Pete Rimmer on 14/09/2019 21:44:44:

I guess you'd need to find an ex-employee from the factory for that, or a drawing.

BTW I had an Denford TDS1 and the cross slide thread on that was clearly cut (or at least finished) with a die. The marks where the die stopped were plain to see.

How are you sure it was a die? Threads cut with an Anjest attachment have a run out like a die as do modern CNC threads no need for an undercut with either.

Steve

I'm not sure, just how it appeared to me. I figured if it was done with an auto knock-off device then the marks would be right at the end of the thread. This appeared to be cut further along then finished slightly short of the end. I only mention it as a matter of interest really.

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