Bolt Sizing Question

[mike7]

This might seem like a dumb question, but does the length of a bolt include the head or just the shank/threads?

 

[94yj]

should be just the length of the shank and not the head

 

[franzdom]

Usually just the threads, there are a few exceptions like flat head screws.

 

[mike7]

Thanks for the quick info guys. Are there any other exceptions in addition to flat head screws?

 

[kenburkholz]

Bolts are measured from under the head to the end. Flat head screws, are measured from the top of the head to the end. Ken.

 

[bob15]

or

or

 

[royesses]

The non-threaded part under the head is known as grip length.

 

[aaronrkelly]

bob15 - very useful info, thanks.

 

[KamiCrit]

Here is an academic reference.

 

[BlackjackNA]

^^^ Yay, Gray!

 

[woody 73]

If you think about for a second as soon as the bolt stops you can only measure just the length that went all the way in.

Same for the bolt with a slight angle at the head, a countersink will allow it to sink further into the material at hand so you would need a full measurement from top to bottom, which makes for perfect sense.