Coventry Die Heads

This topic has 12 replies, 5 voices, and was last updated 21 June 2021 at 11:40 by Nicholas Farr.

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18 June 2021 at 09:53 #550285
Paul Page 1
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@paulpage1
My Coventry Die Heads are missing some threaded parts and I'm struggling to identify what thread form they will be.

1/2" CH Die Head; front plate screws

3/4" CH Die Head; front plate screws; Shank Screw; Closing Spring Screw

Any ideas what Alfred Herbert's designers might have specified back then?

Paul
Advert

18 June 2021 at 09:53 #20337
Paul Page 1
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@paulpage1
Parts
18 June 2021 at 11:31 #550300
alan payne
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@alanpayne54366
All Herbert die head screws were imperial size BSW/BSF/BA. They did not go near metric till early 70's, Doubt if they would have altered specs.

UNC/UNF only used on american licenced tools Devlieg/Microbore

Taps /Dies etc were manufactured at Blackhorse Road Site.

Ex Herbert Apprentice
18 June 2021 at 12:47 #550315
Nicholas Farr
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@nicholasfarr14254
Hi Paul, welcome to the forum and I hope the scan below gives you the information you are looking for.

Regards Nick.
18 June 2021 at 13:44 #550325
Paul Page 1
Participant
@paulpage1
Wow, That is fantastic guys. I'm really glad I joined your forum. I can now get on and refurbish / repair the Die Heads. Thanks for you help.

Paul
18 June 2021 at 14:13 #550331
Anonymous
For Coventry diehead spares contact Wiseman Threading:

Wiseman Threading

I found them helpful when buying spares for rebuilding my Coventry dieheads.

Andrew
18 June 2021 at 16:15 #550343
Nicholas Farr
Participant
@nicholasfarr14254
Hi Paul, I've just noticed that you mentioned CH Die Heads and that I've put the CHS list up, so here's the the CH list.

Regards Nick.
18 June 2021 at 16:39 #550347
Nicholas Farr
Participant
@nicholasfarr14254
Hi, these code letters maybe useful to anyone who has a Coventry Die Head.

Regards Nick.
20 June 2021 at 14:22 #550571
Paul Page 1
Participant
@paulpage1
That makes sense now. I read that CH were non standard threads.

New problem now! what does .136, .155 & .175 refer to?

Paul
20 June 2021 at 14:29 #550574
Emgee
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@emgee
Posted by Paul Page 1 on 20/06/2021 14:22:44:

That makes sense now. I read that CH were non standard threads.

New problem now! what does .136, .155 & .175 refer to?

Paul

Thread diameters in thousands of an inch (1 thou = .001" )

Emgee

Edited By Emgee on 20/06/2021 14:30:32
21 June 2021 at 09:15 #550686
Paul Page 1
Participant
@paulpage1
Sorry, That was badly put by me. It was the thread form that appears to be missing from the chart. I think from the sockets they are 40 TPI so I'm going to turn a .155" x 40TPI Whitworth screw and see if it fits.
21 June 2021 at 10:01 #550694
Emgee
Participant
@emgee
Paul

I checked the screw pitch on a front plate screw and found 40TPI but I had a diameter of .147"

Emgee
21 June 2021 at 11:40 #550721
Nicholas Farr
Participant
@nicholasfarr14254
Hi Paul, it does seem strange that the TPI is not mentioned and there isn't any other information in the scans from a complete booklet publication. 5/32 x 40 ME looks as if it is about the right size though for 0.155, if the TPI is correct, but a 5/32 BSW might work if the TPI happens to be 32. If the threads are 40 TPI, you might get a slightly over size 1/8 x 40 BSW / ME to work for the 0.136 and for the 0.175, a slightly undersize 3/16 x 40 ME might work.

Regards Nick.
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