Whitworth fine ????? That,s a new one for me !

Those threads look like multi-start to me.

Best regards,

Swarf, Mostly!

I too assume that WF in this context is probably Whitworth Form, but when Joseph Whitworth came up with his thread dimensions, it wasn't a British Standard, though obviously later became one, along with a fine thread to become BSW & BSF, so perhaps there was a Whitworth Fine before the BS was added.
I can't find when the finer thread form was originally started.
There's an interesting article on The History of Whitworth here, which includes some info on the origin of the spanner sizes.
http://www.team.net/sol/tech/whitworth-hist.html

Interestingly JW himself proposed a thread series based on decimal, rather than fractional, which did include a 0.2" diameter, though that was in 1897, which rather predates those taps by the looks of it.
https://en.wikisource.org/wiki/Miscellaneous_Papers_on_Mechanical_Subjects/A_Paper_on_Standard_Decimal_Measures_of_Length

Bill

Edited By peak4 on 21/08/2023 22:33:38

Speaking of odd taps and dies ect, like many others, I suspect, I have ended up with a collection of odd taps and a few dies over the years. Most of them are BSW or BSF, not much call for them these days, but it seems a shame to just dump them, but what does one do when you have six or seven of the same size ? [Dont even ask how this came about ! ] Also have a few number and letter drills, very few know what I ,m talking about if I mention "Letter O " drill

Makes me realize just how old I am. I even remember when we used to use 6" rules !!!!

Voice from the back say,s "What were they for ?"

… and for opening your pay packet!

Very generous offer Martin. We are in your neck of the woods in a week or so. If you have one available shall we pop round and pick one up?

Rik

I suspect that the odd size whit tap was used by some manufacturer who wanted to sell spares or service for their product and ensure their service was not easily copied by other suppliers or service providers. some larger dia fine whit form threads were used on optical fittings,ie microscope objectives. Being into vintage engine restoration I cut far more imperial threads than metric or unified and have full sets of imperial,number and letter drills plus metric and they all get used.there have been lots of posts on letter drill/number drill but no real logical explanation of the odd steps in drill diameters though lots of guesses, Imperial drills were logical ,though on fine work the the 1/64 steps are too large, so drills with finer steps were needed though why come up with two series that need to be looked up in table to find their dia .

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For general info. … this illustration can be assumed ‘definitive’ having been published by the Royal Microscopical Society

**LINK** http://www.science-info.net/docs/etc/RMSthread.jpg

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Unfortunately, that’s the best copy I have found.

Posted as a link rather than a photo. because we have interesting times ahead.

MichaelG.

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P.S. __ Whitworth made test gauges for this thread, which were supplied to the major manufacturers in the interests of standardisation [and they are things of great beauty]