# 7/16 -- 9/16 Nuts and bolts Why not 1/2" **URL:** \ **Category:** Factual Questions\ **Created:** [October 22, 2000, 6:47pm UTC](https://boards.straightdope.com/t/7-16-9-16-nuts-and-bolts-why-not-1-2/37893 "2000-10-22T18:47:34Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Anachronism](https://avatars.discourse-cdn.com/v4/letter/a/e56c9b/32.png) [@Anachronism](https://boards.straightdope.com/u/Anachronism)\ **Post date:** [October 22, 2000, 6:47pm UTC](https://boards.straightdope.com/t/7-16-9-16-nuts-and-bolts-why-not-1-2/37893/1 "2000-10-22T18:47:34Z")
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. ---
**Author:** ![justwannano](https://avatars.discourse-cdn.com/v4/letter/j/7ab992/32.png) [@justwannano](https://boards.straightdope.com/u/justwannano)\ **Post date:** [October 22, 2000, 7:06pm UTC](https://boards.straightdope.com/t/7-16-9-16-nuts-and-bolts-why-not-1-2/37893/2 "2000-10-22T19:06:55Z")
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. ---
**Author:** ![Mr.Blue\_Sky](https://avatars.discourse-cdn.com/v4/letter/m/d26b3c/32.png) [@Mr.Blue\_Sky](https://boards.straightdope.com/u/Mr.Blue_Sky)\ **Post date:** [October 22, 2000, 7:33pm UTC](https://boards.straightdope.com/t/7-16-9-16-nuts-and-bolts-why-not-1-2/37893/3 "2000-10-22T19:33:57Z")
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! ---
**Author:** ![Anachronism](https://avatars.discourse-cdn.com/v4/letter/a/e56c9b/32.png) [@Anachronism](https://boards.straightdope.com/u/Anachronism)\ **Post date:** [October 22, 2000, 7:34pm UTC](https://boards.straightdope.com/t/7-16-9-16-nuts-and-bolts-why-not-1-2/37893/4 "2000-10-22T19:34:44Z")
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. ---
**Author:** ![justwannano](https://avatars.discourse-cdn.com/v4/letter/j/7ab992/32.png) [@justwannano](https://boards.straightdope.com/u/justwannano)\ **Post date:** [October 22, 2000, 8:04pm UTC](https://boards.straightdope.com/t/7-16-9-16-nuts-and-bolts-why-not-1-2/37893/5 "2000-10-22T20:04:31Z")
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. ---
**Author:** ![Anachronism](https://avatars.discourse-cdn.com/v4/letter/a/e56c9b/32.png) [@Anachronism](https://boards.straightdope.com/u/Anachronism)\ **Post date:** [October 24, 2000, 12:43pm UTC](https://boards.straightdope.com/t/7-16-9-16-nuts-and-bolts-why-not-1-2/37893/6 "2000-10-24T12:43:58Z")
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 ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [October 24, 2000, 1:14pm UTC](https://boards.straightdope.com/t/7-16-9-16-nuts-and-bolts-why-not-1-2/37893/7 "2000-10-24T13:14:09Z")
Yep! In the U.S., the correct wrench or socket size is 3/16 larger than the body sixe of the bolt. ---
**Author:** ![Myndephuquer](https://avatars.discourse-cdn.com/v4/letter/m/f0a364/32.png) [@Myndephuquer](https://boards.straightdope.com/u/Myndephuquer)\ **Post date:** [October 24, 2000, 1:16pm UTC](https://boards.straightdope.com/t/7-16-9-16-nuts-and-bolts-why-not-1-2/37893/8 "2000-10-24T13:16:09Z")
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. ---
**Author:** ![Anachronism](https://avatars.discourse-cdn.com/v4/letter/a/e56c9b/32.png) [@Anachronism](https://boards.straightdope.com/u/Anachronism)\ **Post date:** [October 24, 2000, 3:18pm UTC](https://boards.straightdope.com/t/7-16-9-16-nuts-and-bolts-why-not-1-2/37893/9 "2000-10-24T15:18:41Z")
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.