Wrench size vs.bolt size?

[jim whitney]

Recently noticed some old wrenches from dads old collection say 3/8 but are actually 11/16 and 7/16 is actually13/16 when did they change from bolt size to head size?

 

[sometoyotaguy]

Some of the British wrenches were like that. Whitworth, I think

 

[jim whitney]

I keep finding these things and it,s totally crazy! Why would you do this?

 

[r_olson_06]

Sounds like British standard to me. That is a good find.

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[padroo]

One of the rules of thumb is bolt head size is one and one half the diameter of the bolt. It isn't perfect but it will get you close on SAT and metric.

Example, 1/2 bolt takes a 3/4 WRENCH.

 

[Mechanical Noise]

Recently noticed some old wrenches from dads old collection say 3/8 but are actually 11/16 and 7/16 is actually13/16 when did they change from bolt size to head size?

I have a few wrenches like that. I think the changeover occurred in the late 20s, probably because stronger bolts with smaller hex heads were becoming common.

 

[woody 73]

Hope this helps you out:

http://alloy-artifacts.org/table_oe_wrench.html

 

[Mark914]

you should probably just ship those "confusing" old wrenches to me.

I read somewhere it was standardized by 1926 - 27, so those wrenches are probably from before that era.

What brands you have? Got any pictures? always love to look at the old stuff.

 

[Flivver250]

Sounds like British standard to me. That is a good find.

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+1 Whitworth sizes. Can use on old Austin Healys and the like.