Fastener Help Req

I think the later. I didn't find a standard for this (but, OTOH, the book is incomplete). At least it says, that M 10 is 16 mm, not 17 mm. SO it can't be so old. ;-)

But its true, I have seen screws with smaller heads, but only in cars. So they are special made.

Nick

Almost certainly special. For instance the standard 8mm nut or head on an

Some older metric standards used different hex sizes, they probably were DIN standards but likely obsolete by now.

I was working on a big marine gearbox a few months ago which had an odd hex size, may well have been the same one you are looking for. Our case had plenty of room for the current standard size of hex, a lot of the bolts & nuts were tired so we just replaced the lot.

I had a Danish BUKH engine some years ago where all the bolt & nut hexes were common metric sizes, only when I tried to renew a bolt did I find that the threads were Whitworth. My guess was that the engine had been designed at a time when lots of Whit was used by scandinavian engineers & they didn't want to change all the threads for compatibility reasons but rather than buying in fasteners from abroad they made their own. Apparently there is/was a DIN standard for that!

Tim

I strongly doubt that! My guess is, that they wanted to hide that they still were stuck to imperial. ;-))

Nick

How many do you want? Peter

A lot of Scandinavian (and some German) agricultural machinery had metric headed Whitworth hardware into the 1970's. The reason for using non-standard heads was that younger farmers and fitters didn't have the right size spanners, the threads were perfectly ok as originally designed :-)

Mark Rand RTFM

In Denmark and Germany, among others, Whitworth thread bolts always came with metric-size hexagon heads. There indeed was a DIN standard for that (DIN 931 and DIN 933 which also covered metric sizes)

If my memory serves me, they were: