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View Full Version : How do I determine fastener size?



LonesomeTriZ
11-15-2009, 08:35 AM
I know this is a simple and almost too stupid of a question to ask but I have never had the need to know how. Whenever I need a fastener of any kind I just match them up with one I have as a guide. Now I want to get all the nuts, bolts, washers, and so on I have organized. I went out and got some storage bins and they are labeled by size. I now have the arduous task of going in and organizing all the randomly stored fasteners I have. Because I have only gone by head size and type, thread style, length, and radius I have no idea what the measurements mean on the bins. Can I get a little assistance in making my work area more organized?

RoscoW
11-15-2009, 09:13 AM
Lonesome is this the type of info your looking for?
http://www.ehow.com/how_4812253_measure-bolt-size.html.

How are your bins labeled?

LonesomeTriZ
11-15-2009, 09:18 AM
Thanks, that is a good start. The bins are lebeled by fractional size. I beleive they mean the thread pitch. I know it is not by the bolt head.

racerxxx
11-15-2009, 09:21 AM
It depends....

Length is measured from under the head for all cap screws(Socket head cap screws button head, pan head etc.), except flat head screws which are measured from the top of the head.

If your looking for thread pitch, the easiest way is using a thread pitch gauge. I work with hardware everyday, so I have gotten the SAE beat into my brain and can pick up a screw and look at the pitch and know what it is(repetetion). from 4-40 all the way 3/4-16. Metric is a whole nother deal on thread pitch---they have so many thead pitches that are so close in pitch it's unreal.

Here is a good resource to research:

http://www.mcmaster.com/#screws/=4ihe2z

On the left you can click on the "All About XXX"

RoscoW
11-15-2009, 10:08 AM
Most bolt bins I've seen are labeled as this, the fractional number will be the diameter of the bolt, and then the number following will be threads per inch followed by the length of the bolt from the underside of the head to the end of the threaded part.
eg:
1/4-20x4
1/4 " diameter bolt with 20 threads per inch at 4" long

1/2-13x2
1/2" diameter bolt with 13 threads per inch at 2" long

Unless you have a very extensive bin set up you probably won't get into the fine thread stuff but if you do the only number to change would be the threads per inch.
eg
1/2-20x2
1/2" diameter bolt with 20 threads per inch at 2" long

Threads may be labeled NC (national coarse) and NF (national fine)
These sizes are also how all taps and dies are labeled.

Ross..

SWIGIN
11-15-2009, 12:31 PM
as a kid back in the 80s i found a super easy way of determining bolt diameter and i still use this method from time to time.

we all have wrenchs, meteric and standard....well they can be looked at as gauges for finding diameters.

before i had micrometers and calipers i found that wrenchs are a perfect gauge to tell me the OD of all kinds of things like bolts, round bar stock, ball bearings, whatever.

they are basically a go no go gauge that we all have and you cant mess up the reading since it's stamped on the tool....lol anyway, this worked for me for over 25 years.

as far as threads go pick up a pitch gauge and your set.

edit.....threads are normally slightly smaller (OD) then the shank of a bolt so the fit in a wrench will be a hair loose

LonesomeTriZ
11-15-2009, 08:44 PM
Thanks, all of that was helpful. That link is awsome, it made things a lot easier. I know this is going to be a pain in the ass, but it will be worth it to have organization.