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 How to determine a thread size
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 Return to top of page · Post #: 1 · Written at 4:58:19 AM on 31 August 2021.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1692

I am needing to find out the thread size on the clock knob for the AWA /Hotpoint clock radios. Its a left handed thread .


 
 Return to top of page · Post #: 2 · Written at 4:50:54 PM on 31 August 2021.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4545

It also has a diameter and a pitch. The one I measured is 2.7mm 7/64"

That would make either a US #5 Guage of 40 TPI, Dutton thread 60 deg;

or a British Association #6 pitch metric pitch 0.53, Thury, or Filière Suisse, FS, screw thread; Thread angle 47.5 deg.

Whitworth thread is 55 deg

This ensures the maximum confusion & hassle and may need to be cut / tapped with a jewellers CNC or similar if its LH thread. Alternatives are looking good.

Marc


 
 Return to top of page · Post #: 3 · Written at 5:06:51 PM on 31 August 2021.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6625

The size is a mystery but Smiths (I am assuming it's a Smiths mech) tended to stick with BA (British Association) threads.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 4 · Written at 8:58:16 PM on 31 August 2021.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4545

Clock here is a Smiths.

You can get into all sorts of trouble with threads some of the stuff here is over a hundred. Automotive decided after WWII to do a bit of standardising. To make things difficult for the enemy & themselves admiralty had one lot of threads & it only got worse from there on especially when they started making Merlin motors in USA.

There is one turn per inch difference in 1/8" BSP pipe & US 1/8". British did have some consistency with Brass. It had its own fixed 26TPI and bike & electrical stuff made of brass was all 26tpi. That saved changing the "change gears" on the lathe to cut threads. Now one has to be careful as the change gears and change box on my lathe is one of many that can cut both metric & Imperial; not withstanding US & British can have different TPI on the same diameter bolt.

Under 1/4" USA uses gauge.

In around 1950 all British and American vehicles standardised on UNF however, spark plugs are mainly Metric eg. Ute & Tractor are 14M1.25.


 
 Return to top of page · Post #: 5 · Written at 5:59:47 PM on 1 September 2021.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1692

Thanks guys this is helping me


 
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