A Real Puzzler

[trusty220]

My mate showed me a spanner yesterday and asked me a question I couldn’t answer because I’d never seen it before. I knew where to ask the question, though!

He had a pretty unusual-looking open ended spanner which had been made in Britain, probably some time in the Fifties or Sixties looking at the style. One end was stamped with 3/4 AF and the other with 11/16 AF- got the picture? Right! Here’s the problem- under the 3/4 AF was also stamped 75 AF and under the 11/16 AF was stamped 69 AF. Has anyone seen these strange sizes before? They were definitely stamped at the same time with one stamp that did both sets of numbers so they must mean something to somebody.

Perhaps the 75 AF was short for 750 thousandths of an inch and the 69 for 690 thou (11/16 is actually .685 thou)- but why? Who would measure hex heads in thousandths of an inch?

I feel sure one of you must know the reason. Put me out of my misery!

[andyfrost]

Geoff .75 would be 3/4 , and .69 11/16 ……..just a thought , seldom do I have a metric head on.

Andy.

[chris]

I used to have ,maybe still do have spanners with this dual marking on, I was taught that AF meant across flats, but my father referred to them as American fine. I never questioned it, it didn’t pay to!

[davidbliss]

All my 1960 Britool tools are stamped the same.

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[charlie]

There is a trader that gets around the vintage shows who in addition to selling new tools also sells good quality old spanners. He has a very good knowledge of the older stuff. If I see him and can remember to ask I will.
I wonder if it would be worth asking the Tool and Trades History Society (TATHS)

[wristpin]

Another oddity , 50p from a bin of assorted at a boot sale . Cheap / expensive paper weight !
I presume that it’s a flare nut spanner for pipe connectors.
Weighs 1.7 lbs.

https://www.datamp.org/patents/displayPatent.php?number=17417&type=RE&country=US

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[trusty220]

I’ve got it’s little brother in my toolbox, Angus! I bought mine for doing the brake pipes on the GT6 and it’s 1/2″ AF- yours is considerably bigger so it’s probably intended for use on hydraulic pipes. A good buy for 50p though!

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