Coventry Die Heads

[Paul Page 1Participant @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

[Paul Page 1Participant @paulpage1]

Parts

[alan payneParticipant @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

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Paul, welcome to the forum and I hope the scan below gives you the information you are looking for.

Regards Nick.

[Paul Page 1Participant @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

[Anonymous]

For Coventry diehead spares contact Wiseman Threading:

Wiseman Threading

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

Andrew

[Nicholas FarrParticipant @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.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, these code letters maybe useful to anyone who has a Coventry Die Head.

Regards Nick.

[Paul Page 1Participant @paulpage1]

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

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

Paul

[EmgeeParticipant @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

[Paul Page 1Participant @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.

[EmgeeParticipant @emgee]

Paul

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

Emgee

[Nicholas FarrParticipant @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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