What nut thread is this? - UK Vintage Radio Repair and Restoration Discussion Forum

Steve_Bell · 22nd Dec 2023, 5:56 pm

I'm referring to the nuts used on panel-mounting toggle switches, fuse holders, etc.

It appears to be 0.5 inch diameter but I would like to know what thread form it is.

barrymagrec · 22nd Dec 2023, 6:04 pm

I have always assumed it was 15/32 UNEF.

Bulgin simply state 15/32 X 32 tpi.

Ed_Dinning · 22nd Dec 2023, 8:50 pm

Hi Steve, I think there were one or two different sizes as the OD varies between makers.

I have a good selection of nuts if you need any

Cheers. Ed

emeritus · 22nd Dec 2023, 9:28 pm

Some rotary switches of continental manufacture (such as Elma) use a M10 x 0.75 thread, but I have never encountered any toggle switches with this thread type. This thread size was also used on the pot and tuning shafts of the car radios made for Ford by Plessey in the late 1960's.

The technical section of the 1936 Bulgin catalogue simply said that all bushes were 15/32" × 32 tpi: the UNEF standard hadn't been established at that date. I would think that manufacturing tolerances would mean that either the 55° Whitworth form or the 60° Unified form would mate in either direction, rather like the 1/4" Whitworth/UNC thread used for attaching cameras to tripods.

pmmunro · 23rd Dec 2023, 5:32 pm

Steve,

Might this be the necessary stimulus to invest in a set of screw thread gauges? Your 'hexode' status suggests that you have, and probably will meet this problem more than once. With a set of screw thread gauges and a digital calliper, you'll never need to wonder again - the thread tables are easily downloaded.

PMM

Steve_Bell · 24th Dec 2023, 9:22 pm

Thanks for all replies. I'll investigate screw thread gauges.

22nd Dec 2023, 5:56 pm	#1
Steve_Bell Hexode Join Date: Sep 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 475	What nut thread is this? I'm referring to the nuts used on panel-mounting toggle switches, fuse holders, etc. It appears to be 0.5 inch diameter but I would like to know what thread form it is.

22nd Dec 2023, 6:04 pm	#2
barrymagrec Octode Join Date: Dec 2017 Location: Morden, Surrey, UK. Posts: 1,562	Re: What nut thread is this? I have always assumed it was 15/32 UNEF. Bulgin simply state 15/32 X 32 tpi. Last edited by barrymagrec; 22nd Dec 2023 at 6:15 pm. Reason: extra info

22nd Dec 2023, 8:50 pm	#3
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,198	Re: What nut thread is this? Hi Steve, I think there were one or two different sizes as the OD varies between makers. I have a good selection of nuts if you need any Cheers. Ed

22nd Dec 2023, 9:28 pm	#4
emeritus Dekatron Join Date: Jan 2012 Location: Brentwood, Essex, UK. Posts: 5,355	Re: What nut thread is this? Some rotary switches of continental manufacture (such as Elma) use a M10 x 0.75 thread, but I have never encountered any toggle switches with this thread type. This thread size was also used on the pot and tuning shafts of the car radios made for Ford by Plessey in the late 1960's. The technical section of the 1936 Bulgin catalogue simply said that all bushes were 15/32" × 32 tpi: the UNEF standard hadn't been established at that date. I would think that manufacturing tolerances would mean that either the 55° Whitworth form or the 60° Unified form would mate in either direction, rather like the 1/4" Whitworth/UNC thread used for attaching cameras to tripods. Last edited by emeritus; 22nd Dec 2023 at 9:53 pm. Reason: typos

23rd Dec 2023, 5:32 pm	#5
pmmunro Octode Join Date: Jul 2004 Location: Dundee, UK. Posts: 1,815	Re: What nut thread is this? Steve, Might this be the necessary stimulus to invest in a set of screw thread gauges? Your 'hexode' status suggests that you have, and probably will meet this problem more than once. With a set of screw thread gauges and a digital calliper, you'll never need to wonder again - the thread tables are easily downloaded. PMM

24th Dec 2023, 9:22 pm	#6
Steve_Bell Hexode Join Date: Sep 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 475	Re: What nut thread is this? Thanks for all replies. I'll investigate screw thread gauges.