Pine Bed Frame - Mystery Bolts

[bigalxyz]

Hello forum,

I'm repairing an old pine bed frame. It had 4 big allen bolts, one in each corner, which screw into some kind of little threaded sleeve. However 3 of the 4 bolts has gone missing.

I'm struggling to replace them because I don't know what they're called, how to describe their size, etc.

See attached photo. On the left is a nice new M8 bolt with a 1mm thread. The slightly rusty one on the right is the mystery bolt which seems to have the same 8mm diameter but the thread is just under 2mm - very coarse. Does anyone know what these bolts are called & where I could buy some please?

Thanks,
Alan

 

[just pumps]

It is an Allen countersunk head screw, 8mm = 5/16", the secret is to count the TPI (Threads per inch). BSF = 22 tpi, Whitworth = 18 tpi, but then it could be UNF or UNC and metric sizes can be fine or coarse threads.

 

[bigalxyz]

Thanks. Looks to me like 14 threads per inch. Does that help? *runs for Google*

 

[bigalxyz]

So is this an old imperial size? 14tpi with 5/16" diameter seems to be an unknown combination

 

[just pumps]

TBH I would be very surprised if it was imperial but you said in the OP that you tried the 8mm bolt or did I mis read something.

 

[bigalxyz]

Yes the diameter looks exactly the same as the M8 bolt ie 8mm. From a bed made I think in the late 1980s (so probably not worth investing a huge amount of effort in!) - would everything have been metric by then? 14tpi would mean a thread pitch of about 1.8mm I think.

 

[just pumps]

Have you tried the 8mm bolt in the sleeve, does it screw in? 99.9% thinking metric.

 

[bigalxyz]

It fits in the sleeve, yes - but I can only tighten about a quarter turn (if that) because obviously the thread's not right so it gets stuck.

 

[just pumps]

Not 8mm then, can you take the old bolt to a engineering suppliers where they can match it or change the sleeve for a new nut?

 

[bigalxyz]

Not sure where I'd find such a place - although I've found a couple of suppliers online (who seem to specialise in obscure/unusual sizes) so I've just emailed the photo/measurements to them to see if they can advise.