If a hex head bolt is listed as M3 x 4mm does it mean that it's an M3 bolt with a 4mm hex key hole?
I would take it to be a 4mm long M3 thread
Oh yeah that makes much more sense. It was a generic picture...
+1 to that ^. Nothing to do with the hex key size
4mm refers to length; socket size will probably be 2 or 2.5mm.
4mm refers to length; socket size will probably be 2 or 2.5mm.
If it is described as 'hex head bolt' it should have an external hexagon head - usually 5.5mm AF for M3.
Something with an internal hex would be a 'socket head cap screw'.
4mm would be the length of the threaded part only - the overall length would be longer to accomodate the head in either case. (For countersunk heads, the 4mm would be the overall length.)
For extra pedant points, if they are fully threaded, they should be called set screws, or machine screws. Bolt implies partially threaded, but I doubt you'd get pulled up on it outside of a fitting shop.
tilly - the jury have voted and award you...10 pedant points!
Stewards enquiry.
Surely achieved 10 pedant points when pedanting the answer to the question. He then goes forth to claim a bonus point which he backed up with facts.
I therefore award the additional point.
11points and a approving nod
Further pedantry - below a certain thread length bolts are also fully threaded.
For extra pedant points...
Sorry, further stewards' enquiry won't allow that point. My local supplier says that there's no such definition, the nearest that he can come up with is that you put a nut on a bolt, anything else is a screw, 🙂
Anyway, you only implied it. Point deducted for lack of conviction :).
Pedant clarification - the head type distinguishes between Machine Screws and Machine Bolts. Machine screws have a slotted head, whereas bolts have a hex head. With a slotted head, machine screws can be installed using a screwdriver, such as a Philips head or flat-heat screwdriver.
Beginners Guide to fixings pedantry : https://monroeengineering.com/blog/category/beginners-guides/
Yeah, whoever heard of a boltdriver?