Hello,

I bought some hex 3/8 bolts and nuts.

Yes, the O.D. of the bolt appears to be 3/8.

But a wrench that is marked 3/8 does not fit the head of the bolt.

Is there some "standard" where you can tell beforehand, for a given
diameter (size) of bolt, what wrench to use for its head ?

Thanks,
Bob

On 05/11/2015 03:45 PM, Bob wrote:
Hello,

I bought some hex 3/8 bolts and nuts.

Yes, the O.D. of the bolt appears to be 3/8.

But a wrench that is marked 3/8 does not fit the head of the bolt.

Is there some "standard" where you can tell beforehand, for a given diameter (size) of bolt, what wrench to use for its head ?

Thanks,
Bob

Is there some web site where an inquisitive person can search for arcane stuff?

On Mon, 11 May 2015 15:45:06 -0400, Bob wrote:

Hello,

I bought some hex 3/8 bolts and nuts.

Yes, the O.D. of the bolt appears to be 3/8.

But a wrench that is marked 3/8 does not fit the head of the bolt.

Is there some "standard" where you can tell beforehand, for a given
diameter (size) of bolt, what wrench to use for its head ?

Thanks,
Bob
SAE standards for bolt / wrench sizes are available on the net or in
any mechanics text.
1.4"bolt 7/16 wrench
5/16" bolt 1/2" wrench
3/8" bolt 9/16" wrench
etc

The old witworth /bsf system is the only system that marked the wrench
with the bolt size - and 1 3/8" witworth was different than a 3/8" bsf
if I remember correctly.

On 5/11/15 3:45 PM, Bob wrote:
Hello,

I bought some hex 3/8 bolts and nuts.

Yes, the O.D. of the bolt appears to be 3/8.

But a wrench that is marked 3/8 does not fit the head of the bolt.

Is there some "standard" where you can tell beforehand, for a given
diameter (size) of bolt, what wrench to use for its head ?

Thanks,
Bob

You double the numerator and add the denominator. Let me walk you
through this one to show how easy it is. 3*2+8=14mm.

Before I figured that out, I always used slipjoint pliers. I still use
them when I don't have my calculator with me.

J Burns presented the following explanation :
On 5/11/15 3:45 PM, Bob wrote:
Hello,

I bought some hex 3/8 bolts and nuts.

Yes, the O.D. of the bolt appears to be 3/8.

But a wrench that is marked 3/8 does not fit the head of the bolt.

Is there some "standard" where you can tell beforehand, for a given
diameter (size) of bolt, what wrench to use for its head ?

Thanks,
Bob

You double the numerator and add the denominator. Let me walk you through
this one to show how easy it is. 3*2+8=14mm.

Before I figured that out, I always used slipjoint pliers. I still use them
when I don't have my calculator with me.

You would be banned from most professioal workshops. B-)

A much better way if you don't know is to just choose the one that fits
nice and snug. B-)

--
John G Sydney.