Standard Or Common Bolt And Nut

Thank you very much for your help.

I would guess Japan wants metric bolting and USA wants unified. It wouldn't be hard to put both requirements in a single standard, but I don't know if anybody has.

Besides Metric and SAE Standards. Nuts and bolts have two standards. One is how many threads per inch (SAE) the other is how hard is the metal. On SAE ( the standard used in the USA such as 1/2 inch and 1/16 inch as compared to Metric 8 and or 10 for example as sizes. But On SAE Bolts you will see lines on the top of the bolt. Those line tell how hard the metal is. The more lines the harder the metal. A few years ago The FAA was found to be allowing for or at least not doing a thing about mislabeling the amount of lines on the top of a bolt. On Aircraft this is very important as it would be on such things as breaks on a car or the bolts that hold the wheels on the car. But if purchased from a brand name USA Made source you can be pretty sure the hardness is correct. But SAE would be a good place to start and they would know where to find standards for Metric. They may even have those standards on hand but they would not make them as so many countries use Metric. As a Side Note. I always kind of laff when I think about some mechanic in some other country working on a USA made car or truck etc.. And Trying to figure out what is the size of that bolt and what wrench size do I need if the first wrench was to small. We are all used to knowing that 9/16 is a little larger than 1/2 and 5/8 is normally the next step up if we are using standard car bold sizes that increase by 1/16 th of a inch. But on more critical parts of the unit the sizes increase by 1/32 of an inch thus a wrench that is 17/32 for example. They are used to Size 1 , 2 ,3 ,4 ,5 etc,,, With us it is 17/32 then 15/64 Th etc.. To them they must be very frustrated and think we are Nuts or that we are very smart. Regardless the metric is much easier but it is funny to think of the rest of the world trying to figure out our SAE System. Makes me laugh. I hope the threads per inch and the hardness Marks help you. Jim Davison

Good point about hardness etc if it's a critical application. Not sure how it's covered in metric, there are marking for strength grade, maybe hardness is included in the standard. Ref thread pitch, it's covered by the bolt designation, UNF, UNC, metric coarse or fine. But one of the advantages of metric is that coarse is a good compromise and is what you get if you don't specify, so simplifies ordering. Fine is only supplied for special purposes.

With wrench sizes, I believe most of the sizes you get in a standard set for unified have a nut A/F to correspond (though some are a lot more common than others). But with metric, for normal handyman range up to about 36mm A/F you get every size in whole mm, rather than just the "right" ones - M5-8mm, M6-10mm.....M24-36mm, so many of them don't get used at all. Though that can be an advantage as sometimes a non-standard size is used. On cars - I've found 12mm and 15mm heads on metric bolts. Be good if everybody stuck to the standard!

Check out the Conveyor Equipment Manufacturers Association:

http://www.cemanet.org/

On my Ford, if it is one side of a part it is metric, the other side is SAE. Keeps one set of tools from getting rusty. -- JHF

Half the machinery in the plant here is 'mixed standard.' mostly due to older components using SAE and newer ones using metric, except for pieces designed as 'legacy replacements,' which will predominately use SAE.

The horror is that many bolts here are Socket Head Cap Screws or Button Head Cap Screws. Both use an Allan wrench to turn, Some use metric wrenches, others use Imperial, and there's no way to tell which is which without fitting every wrench and seeing which one mates of perfectly (or forcing things with an 'almost right' sized wrench, depending on who is removing/tightening the bolt.)

Or worse yet, using the next smaller size and rounding the straight sides.

That is exactly what I was alluding to, destroying the head by using the closest 'wrong standard' wrench that fit.