Why are 7/16" and 9/16" nuts and bolts so common. Wouldn’t it be easier to use 1/2"? Most places I see these 1/16 of an inch bigger or smaller couldn’t possble make a difference.
Standard size nuts and bolt are enough of a pain in the ass already, couldn’t they save 7/16 and 9/16 for situations where the 1/16" would really make a difference.
I’m not sure what your Question is. They do use 1/2" nuts and bolts in a lot of situations.It depends on the holding power you want.There are also three common hardness ratings for bolts. Look on the head of the bolt. Three marks indicates a number 5. Five marks indicates a number 8.When there are no marks it is not considered a hard bolt.The unhardened are good for most wood projects and metal when stress is not an issue. The number 5 is good for most metal work and the 8 is used it heavy equipment when the bolt is under a lot of stress.
It’s really part of the great “Nut Manufacturers Conspiracy” to keep nut makers in business! You think nuts are, well, nuts? Check out the gazillion types of screws that exist!
It seems to me 9/16 and 7/16 are much more common then 1/2 in situations where 1/16th of an inch could not make a significant difference in holding power. The hardness of the bolts is a separate issue.
My question is couldn’t manufactures just use 1/2" instead of 9/16 or 7/16 when 1/16 wouldn’t make a difference. 1/2" seems like a much rounder number, why do they choose the “odd” 9/16 or 7/16.
Jim I think you are confusing the size of the hex stock used to make the bolt with the size of the bolt. A 1/4 inch bolt is made from 7/16 hex stock so uses 7/16 wrench Obviously the 1/4 inch bolt fits into a 1/4 inch hole.
The 7/16 bolt is used mostly in machine work although you’ll find it in automotive use. Often times they are fine threaded.
Obviously a larger bolt than is necessary would make the object heavier and in some cases maybe weaker. There are engineering standards for such things. I do not know who made up the standards or when they were set.
I didn’t even consider the bolt size, If a 1/4 inch bolt equals a 7/16 head I assume a 9/16 head equals 3/8 bolt.
1/4 and 3/8 are much “rounder” numbers, thanks justwannano
Yep! In the U.S., the correct wrench or socket size is 3/16 larger than the body sixe of the bolt.
jimshep, what are you working on? Do you think that 1/2" fasteners are being discriminated against? You sound angry at “the machine”.
Not counting all of my previous American-made vehicles, I currently have a Harley, a Bayliner boat, and a Jeep (not to mention my foreign made vehicles), and my 1/2" and 9/16" open-end/box-end wrenches and my 1/2" - 9/16" combination box-end wrench are often the only wrenches that I confidently carry around in my ‘traveling’ tool kit. As for my foreign-made vehicles, I find myself most often using a 13 mm wrench on the bolts (13 mm ~= 1/2") (I just changed a water pump this past weekend on a foreign vehicle (I had to take the $@*& timing belt off to get to the water pump!! :mad: ), so this was a re-confirmation of my first-hand knowledge. I will have to admit that there were a lot of 10 mm nuts and bolts, too.)
What are you working on? As far as ‘American made’ vehicles go, I have always felt that 'if that bolt ain’t a 1/2 inch, ‘must be a 9/16th’. 
btw, good answers, justwannano.
Myndephuquer, yes I did kind of feel 1/2" bolts where kind of being discriminated against since it is a nice round number(well as far as fractions go). If “the machine” would stick to certain sizes when possible we would have to carry around less tools.
I have notice the more popular 9/16 and 7/16 for a while now, but when I went to put up my direcTV system half the nut/bolts where 7/16 and half were 9/16 and of course the cable conections are 7/16.
BTW - I can take apart 90% of my (pedal) bike with a 5mm allen key. They even put a 5mm head on different size bolts. But a bike is desighned to be repaired with a very small toolkit.