M6 Bolt Size

M means metric and 6 means nominal 6mm diameter

Yes, the unthreaded part (if any) of the shank is 6mm diameter. The major diameter of the thread is a little less as the tops of the threads are rounded. M6 bolt head and nut are 10mm across flats.

Cheers........Codey

I thought that 6mm was actually the major diameter, but I could be wrong.

Hello Holzfeller

You might be right. The drawing I have shows dotted lines meeting at a theoretical point, but the actual thread form rounded off below that. Shows dimension H for thread depth between these theoretical points, so for M6, pitch 1 mm, H = 0.5/tan 30° = 0.866 mm. Distance from tip of rounded thread to the theoretical point = H/8 = 0.11 mm. I assumed the 6 mm is between the theoretical points, making actual diameter about 5.8 mm. But I could be wrong, it doesn't give distances from the bolt axis so can't tell from the drawing. I might measure one sometime!

Cheers.......Codey

Hello Codey,

Yes, some of these drawings are not so obvious & need careful reading. It just happens I was looking at M6 & M8 thread dimensions at the weekend, checking some screws for which I need to tap some holes. I'll re-measure them later.

Why does the <...we say that...> if it doesn't know <...what...M6 mean[s]...>?