Starter dog thread

[Colin Wilks]

Wanting to make up a pusher to mount the front bearings. My starter dog measures 5/8" over the threads but is 16 tpi, not the 14 I would expect for standard bsf. Is this thread a bastard size?

[Steve Jones]

Yes Colin. Same as half shaft thread. The starter dog thread continued post war until such times as BMC stopped fitting starting handles I think.

Steve

[PhilM]

I believe it may be a 5/8" Whitform thread, I've just had the same problem with the thread on the gearbox output flange nut which I think may be the same size.

If you look on the Tracey Tools website you will see that 5/8" whitform is available in several thread pitches including 16.

Hope this helps,   ..... Phil.

[Bill Sheehan]

Not being an engineer, I must confess I'd never heard of Whitform until recently.  But I was informed yonks ago that the half-shaft and starter dog threads were an Admiralty thread, acquired from Austin's war efforts over WW1.  Are the threads the same, or was I misinformed?  Incidentally, the louvres on genuine Ulsters were metric, so not everything on a Seven was Whit or BSF as is generally accepted.  Perhaps strange threads elsewhere as well?  Cheers,  Bill in Oz

[Ray White]

Blowed if I know what a Whitform thread is? I can't find anything on the net and Google thinks I mean Whitworth so it changes my search entry.

I have found a range of taps and dies supplied by Tracy tools

https://www.tracytools.com/taps-and-dies...ies?page=5

[Bob Culver]

Whitworth form, as Whitworth, BSF, BSP. The cross sectional shape of the thread; angle, finish at top and bottom, tolerance ranges etc. 55 deg included angle of the peaks instead of 60deg of SAE, AN, Unified, SI, ISO. In several sizes Whit threads and UNC same pitch but the form differs. Interchange for rough work. Books like Machinery's Handbook cover.
Whitform may be applied to any pitch as a special, which some Seven threads are. I guess it safeguarded against substiute of low strength common parts with consequent troubles.

[Ruairidh Dunford]

Incidentally, the louvres on genuine Ulsters were metric, so not everything on a Seven was Whit or BSF as is generally accepted.  Perhaps strange threads elsewhere as well?  Cheers,  Bill in Oz

Starter bendix spring retaining bolts in Bacon Slicer type are metric, so are the early zenith carb. threads.

[Chris KC]

Google knows a lot about Justin Bieber and Britney Spears. Not so hot on anything old or deeply technical. It's easy to forget what a treasure A7 Friends is!

[Bill Sheehan]

Chris - And I'm disturbed to run across adults these days who don't know what an Austin Seven is!  One local who claimed to have an Seven in his earlier days even sent me to a nearby town and a paddock with several Austin Sevens - he was probably right, but they were of the A30 variety.   Cheers,  Bill in Oz

[Tony Press]

Bill,

I would think that Whitform is a modern messing about with Whitworth Form Thread- as originaly devised by Joseph Whitworth in 1841.- later adopted as the British Standard Whitworth Form BSW Thread and the fine version BSF.

I do not like Whitform but as the world seems to be into making up words I suppose it will be broadly used

I wonder if they will call the American thread form the Uniform !