Threads on Stauart Safety Valves

[Colin HeseltineParticipant @colinheseltine48622]

I have a Stuart 504 boiler and need to make a blanking plug for the safety valve. I appears to be a 5/16" x 26 tpi. Need to purchase suitable tap and die. Is it going to be a BSB (British Standard Brass or a BSC (British Standard Cycle). These are both available at 5/16"x26. I would guess BSB but would like confirmation before ordering.

Thanks,

Colin

Edited By Colin Heseltine on 23/08/2023 20:10:58

[Colin HeseltineParticipant @colinheseltine48622]

[JasonBModerator @jasonb]

My old paper catalogue lists them as brass and if you look on Stuarts's site under tools the 5/16" x 26tpi taps and dies are BSB

[Colin HeseltineParticipant @colinheseltine48622]

Jason,

Many thanks. Tap and Die now ordered.

Regards,

Colin

[Clive Brown 1Participant @clivebrown1]

Pedant alert! although often used, the term "BSB" is incorrect, there isn't a BS for Brass Threads AFAIK.

My copy of Machinery's Handbook doesn't seem to mention Brass Thread, or Cycle Thread for that matter, but In 50+ years of model engineering I can't ever remember seeing Cycle Thread specified in a design, always Brass for 26 tpi.

[noel shelleyParticipant @noelshelley55608]

My copy of The metalworkers Data Book (2009 ) lists BSB and tells me that like many old british threads it is witworth form WF. Interestingly it does NOT give a thread form for the other 26tpi system, BSC, is it 55*, 60* or some other ? Noel.

[JasonBModerator @jasonb]

Cycle is 60deg

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