Bolt Hex vs Wrench Size
Bolt Hex vs Wrench Size
(OP)
When a bolt head hex is designed for a 3/8" wrench - which is supposed to be 3/8" (the bolt hex or the wrench) and what is the standard clearance/tolerance?
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Bolt Hex vs Wrench Size
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Bolt Hex vs Wrench SizeBolt Hex vs Wrench Size(OP)
When a bolt head hex is designed for a 3/8" wrench - which is supposed to be 3/8" (the bolt hex or the wrench) and what is the standard clearance/tolerance?
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RE: Bolt Hex vs Wrench Size
A good source for all of that kind of information, and much cheaper than buying all the relevant spec's., is any copy you can find of the Machinery's Handbook (esp. if you buy an older, used copy). I started my career with a borrowed copy dated ca. 1930's, now own my wife's old copy (19th ed., 1970), and we also have a couple of more modern versions lying around. Surprisingly :) there hasn't been much change to standard bolt hex and wrench tolerances over the years... can you imagine the outcry if millions of backyard mechanics had to throw out their trusty Snap-On's every 10 years or so?
RE: Bolt Hex vs Wrench Size
htt
David Baird
Sr Controls Designer
EET degree.
Journeyman Electrician.
RE: Bolt Hex vs Wrench Size
Anybody have an idea if metric wrenches are similar in their relationship to the bolt hex?
RE: Bolt Hex vs Wrench Size
RE: Bolt Hex vs Wrench Size
Example 3/8" bolt head size is 3/8" + 3/16" = 9/16" hex size.
The old standard for nuts was to add 1/8" making the nut hex 3/8" + 3/16" + 1/8" =11/16" , but now the nut and bolt hex are the same except in the heavy hex nut series.
Never toss old machinery's handbooks, some of the newer ones edit out specifications they consider obsolete, but are still very much alive in the older machinery.
RE: Bolt Hex vs Wrench Size
The hex size is 1 1/2 times the threaded shank of the bolt in question. So your 3/8 NC bolt will have a hex size of 1.5(0.375 in)= 0.562 in = 9/16". Incidently the height of the hex is exactly equal to the threaded diameter or 3/8".
This is obvious from the Machinist Handbook, to which I concur, is perhaps the best readily available source.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Bolt Hex vs Wrench Size
RE: Bolt Hex vs Wrench Size
RE: Bolt Hex vs Wrench Size
RE: Bolt Hex vs Wrench Size
----- Tolerance (mm) ----
min max (tol max (tol
class 1) class 2)
3<=s< 4 +0.02 +0.10 +0.14
4<=s< 6 +0.02 +0.12 +0.16
6<=s<10 +0.03 +0.15 +0.19
10<=s<12 +0.04 +0.19 +0.24
12<=s<14 +0.04 +0.24 +0.30
14<=s<17 +0.05 +0.27 +0.35
17<=s<19 +0.05 +0.30 +0.40
19<=s<26 +0.06 +0.36 +0.46
For open wrenches, only tolerance class 1 is used. For closed wrenches and socket wrenches, manufacturers are free to choose either tolerance class 1 or 2. I don't know which class is more common; I haven't checked.
RE: Bolt Hex vs Wrench Size
Good Luck
johnwm
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RE: Bolt Hex vs Wrench Size
My Machinery'shows wrench opening tolerances on page 1435. the Twenty Fifth Edition.
Next time I'll slow down when reding posts.
Bob Creely
RE: Bolt Hex vs Wrench Size
RE: Bolt Hex vs Wrench Size
What I did find in the MH for inch wrench opening tolerances is the methodology used to calculate their numbers.
Min opening = 1.005W + 0.001in
Max opening = 1.01W + 0.005in
W is the basic width of the nut flats (ie max nut size)
This seems to be a little different from the ISO metric standard vonlueke posted.
RE: Bolt Hex vs Wrench Size
now I'm wondering too. We've got the 24th ed., and it doesn't have metric wrench opening tolerances. BTW, the 19th ed. on my desk has the ISO metric bolt head tolerances, and they didn't change relative to the 24 ed.
The inch formula works (iff you convert from mm to inches, then back again), but gives an opening that is within (i.e. tighter than) the metric "class 1" tolerances.
RE: Bolt Hex vs Wrench Size
Jess