Tool Talk
Wrench Forum => Wrench Forum => Topic started by: cactus on May 29, 2013, 04:26:17 AM
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Chaps
Just cleaned this spanner (OK wrench) and it seem to me that the sizes as stamped are not quite right.
I always thought SAE sizes were same as A/F sizes?
In this example -the small end has jaws marked 1/2" SAE Gap 3/4", similar strange sizes on the big end, see pic.
Now I know this is an English wrench buy the maker - Armstrong Stevens of Willenhall, so this forum may not be familiar with
them.
Regardless, how do we explain the sizes?
Cheers
cactus
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SAE 1/2 = Screw size 3/4 = Nut size
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SAE was not originally an AF size, it was the US light bolt guage, there was light SAE (which was adopted by automotive), medium CAP (sometimes, sometimes not identified in any particular way) and Heavy (USS) sizes.
I have not seen the 'GAP' nomenclature before, but I guess it was an alternative to AF...
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If I recall correctly, Whitworth wrenches are marked for the bolt/cap screw diameter, not the head diameter; and different thread pitches would use different head sizes for the same major diameter. So, if these wrenches were made by a British manufacturer, it may have been an attempt to inform both British mechanics, who presumably were in the habit of looking at the diameter of the bolt, and American mechanics, who would look at the diameter of the bolt head.
Every time I see a Whitworth wrench, I shake my head in admiration of the work habits of British mechanics, who would have to learn such a complex set of information in order to be able to get the correct wrench out of the toolbox.