# Nut & Bolt Sizes.



## wm460 (Mar 11, 2017)

What are  the most common Nut & Bolt sizes in both metric and imperial?
I have been trying to sort out my lifetime collection of Nut & Bolts, about  6 x 4 Lts container full,  I keep finding these strange sizes, for me any way, like 9.5 mm, 6.75 mm, etc  that will not match up with any of my thread gauges.


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## Nick Hulme (Mar 11, 2017)

Keep them all and buy some more thread gauges ;-)


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## stevehuckss396 (Mar 11, 2017)

Here is a little help with the imperial. Threads should all be the same regardless of the type of head.


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## Blogwitch (Mar 12, 2017)

Here are a couple of tapping charts that might overcome your problem.

The 'All Threads' download one will only work with Adobe reader 7 and above. I had to do this to reduce the size of the file so it would fit into the allowable upload size of this site, but you should be able to download the latest reader for free off the 'net'. It gives details of all sorts of threads, going up in size up to 1" diameter.

This big tapping chart is just that, all the usual threads with the data required to cut the internal thread. 







Hope this helps.


John 

View attachment All threads.pdf


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## Hopper (Mar 12, 2017)

Remember too that many commercial bolts are made quite a bit undersize to allow working clearance. Plus they can get worn down after years of use (or years of rattling around in 4lt cans of bolts!).

I have found it quicker to use a pair of drill gauges, one metric and one imperial, to measure bolt sizes when sorting. Goes much quicker than miking or calipering each bolt etc. The drill gauges are just the cheapo flat stainless steel type with the holes in half millimeter or 1/64" steps punched into them and labelled with size. 

Another easy way is instead of using thread gauges on each bolt to determine pitch and therefore if it is UNF, BSF or Metric, is to get a collection of nuts of known sizes in each thread type, mount them on a board etc and simply check which ones screw onto the bolt.


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## rodw (Mar 12, 2017)

I would say your collection contains some imperial threads. Here are the metric sizes
http://www.metrication.com/engineering/threads.html

Most bolts I buy are about 0.2mm undersize. If it were me, I'd toss out anything that was not a metric thread on account of banning imperial tape measures from my shed many years ago....


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## Blogwitch (Mar 12, 2017)

Rod, 
You have to be careful with metric threads, they are not as generic, like your charts show, that you think they are. It can cause major problems when things 'coming through the door' need to be checked for size.

As an example, Mo'sickle makers have a tendency to invent their own metric sizes based on the thread shape and size that aren't used anywhere else, so you must try to calculate it out so that you can make a tap or thread cut to fit. I use a tap that is 4.5 metric fine for cutting the threads for the Ronson filling valve of rechargeable gas tanks, and I had a pigs own of a job cutting right and left hand threads for a Ducatti fuel tank on/off taps, purely because they were not a standard 'Metric' size and to make it even more difficult, the originals were cast out monkey metal and partially stripped which were all over the place with reference to dimensions. If I remember rightly, they were something like 13mm fine.

John


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