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Nuts And Bolts Explained

Products Explained Nuts And Bolts Explained

It is easy to get confused when buying nuts and bolts. There are a plethora of different types available. Not just the style of them, for example; coach bolts, set screws, machine screws, to name a few, but what size they are. Hopefully this should help you find what size of bolt and nut you need.

Nuts and bolts..JPG


You may recognise the bigger nuts and bolts in the above photo, they are in fact Series leaf spring shackle bolts…the others, well some bits and bobs off the bench.

Nuts and bolts 2.jpg


Okay, have a look at the above sketch. You will see that the spanner size is the actual physical size of the hexagonal part of the nut. This is one thing that causes confusion, asking for nuts and bolts using the spanner size. No, you are supposed to ask for nuts and bolts using the thread diameter.

The diameter is the size of the shank (the unthreaded part of the bolt) and the outside size of the threaded part . So, for example, a ¼" BSF threaded bolt is ¼" in diameter.

A bolts length is always measured from beneath the head to the end of the bolt. Unless it's a countersunk bolt, in which case it's from the top of the bolt. The entire length of the bolt.

In imperial sizes, thread and spanner sizes are given below

BSF sizes

Diameter...................Threads per inch.............Spanner size.

¼".....................................26...........................7/16"
5/16"..................................22...........................17/32"
3/8"...................................20............................19/32"
7/16".................................18............................45/64"
½".....................................16............................13/16"
9/16"..................................16............................59/64"
5/8"...................................14.............................1"
¾".....................................12.............................1 3/16"
1"......................................10.............................1 15/32"

Some odd spanner sizes there eh? Though, I do have most of them in the tool box!

Now for UNF sizes..these make a bit more 'normal' reading.

Diameter..................Threads per inch..................Spanner size.

¼".....................................28.............................7/16"
5/16"..................................24.............................½"
3/8"...................................24..............................9/16"
7/16"..................................20..............................5/8"
½".....................................20...............................¾"
9/16"..................................18...............................7/8"
5/8"....................................18..............................15/16"
¾"......................................16..............................1 1/8"
1".......................................12...............................1 ½"

And finally, last but not least…

Metric Sizes.

Size...........................Thread pitch.....................Spanner size
M6 (6mm)......................1.00mm.............................10mm
M8 (8mm)......................1.25mm.............................13mm
M10 (10mm)...................1.50mm.............................17mm
M12 (12mm)..................1.75mm.............................19mm


So, hopefully now you can see what information you need to have to hand when ordering your nuts and bolts!

Happy Landying!

Here's a handy list of different thread and bolt sizes, to help you identify that random bolt in the spares box...


By @Keeper_of_Tess
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Big Sandy
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    Here's a handy sheet with different sizes and measurements, to help identify that random...

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Really useful @big sandy thank you. Came in useful today when starting my tailgate mod and needing to know bolt length to pass through the tailgate . Now if only I could use a measuring stick accurately 😳😳
Good clear explanation Sandy. Thanks.
A very useful resource. Awesome
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