This is one for the machinists among us. Having purchased an LAL BSB tap and die set, I realised there was an extra tap included in the set. It wasn't on the list on the lid and a quick Google search did not find any reference to a possible use for this type of tap So, does anyone know what a 15/32 26tpi thread was used on or in? Its the sort of size that looks like it could have something to do with lanterns or stoves. Any ideas?
It must be a customized thread size. Definitely Non-Standard. Is it stamped "15/32 - 26" ? I don't know where that would fit on lanterns.
Both B.S.B. and B.S.C. are 26t.p.i., the difference is B.S.B. is Whitworth form i.e.thread angle of 55° whereas B.S.C. is 60°
The tap was included in a Lehmann Archer Lane set of BSB taps and dies As you can see, it's a genuine LAL tap, 15/32 x 26tpi. It's also marked WF' which I assume refers to 'Whitworth Form, meaning it has a thread angle of 55° I might have a look at some Tilley parts to see if its anything to do with them. PS. I had to source a few replacement parts as the set wasn't complete. The eagle eyed among you will notice that the 1/4" die is BSF which happens to be identical to BSB for this particular size. Unfortunately I had to be content with alternative makes for the 1/4' and 3/8' taps - A.N. Other and Apex respectively. Over the last year I've started to become such a tap & die nerd
I thought I'd found out what its for. I tried it in the central boss of a Tilley 246b tank and it fit. It was a little loose but no more so than an aluminium control valve. The pitch is the same at 26tpi but it was a tiny bit loose so I tried a 1/2 inch..... a perfect fit, so its back to the drawing board Dammit!!!
That is an oddball size! I would hazard a bet at fuel system/carburettor type threads possibly An oddball size I have is 5/32" WW, which I used to clean air-adjustment screws in a 1930s Villiers Carburettor. I believe its the same or very similar to the thread used in meccano sets. Alec.
Its very odd indeed and having searched high and low i can find next to nothing about it anywhere. It's only 1/32 smaller than 1/2" BSB thread... that's 1/64th difference either side which is almost negligible (.39mm!). I wondered if someone used it to cut a threaded hole for a worn nut or threaded component to achieve a tight fit. Anyhow, its a nice thing to have, just very curious.
I've made a discovery! The tap is the same thread that is used on the burner bell of an Optimus 8R! As a test, I tapped a piece of 3mm aluminium and it fits perfectly! Mystery solved!
