Petrol tap thread

[BazyleParticipant @bazyle]

Got a small lawnmower petrol tap similar to this as used on some old qualcast mowers I think.

The thread seems to be 3/8 dia tapered and about 29 tpi. ie between 28 and 30 on my thread gauge and not matching a metric one either. Finer than common fasteners, not as fine as UNEF(32tpi). Anyone know the standard?

in passing came across this which didn't help but is an interesting list of threads.

[BazyleParticipant @bazyle]

for lawnmower tap

[Bob YouldonParticipant @bobyouldon45599]

Whato Baz,

Try 1/8" BSP

Regards,

Bob

[Maurice TaylorParticipant @mauricetaylor82093]

I made a fitting for a 30 year old Qualcast petrol tank about a year ago and it was 1/8" BSP

[BazyleParticipant @bazyle]

Thanks, I looked at 1/4 BSP tpi as I thought the differences between name and sixe was only one step not two so should have been more attentive to the dimensions. I think I have a tap, somewhere…….

[Nick HughesParticipant @nickhughes97026]

Seems youv'e found the thread.

Here's a link to some obscure and standard threads: **LINK**

Nick.

[Tim StevensParticipant @timstevens64731]

Remember that there are two versions of British Standard Pipe Thread – one Parallel (for proper tightening against a washer, etc) and Tapered (to tighten into the hole, often using some sort of filler compound). The Parallel version is the same pitch, and fits about half-way along the Tapered when they are screwed to gether, so you can be caught out.

Cheers, Tim

[BazyleParticipant @bazyle]

well I found my tap (screw thread for cutting) and it is tapered

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