Determing missing bolt size from its nut

[Eddles]

Hi all,

So I've got this cupboard that I can't afford to replace (it's much nicer than your average one that is) but I've lost all the fittings required to re-assemble it after a recent move. Most of the fittings are screws which I can use from my own collection, no problem.

However, it also needs 12 bolts and I'm having slight difficulty in figuring out the correct bolt size. The nuts are set in the wood itself so I can't remove them, and I can't drive new bolts through the wood as it'd show up on the outside which is obviously undesirable.

I've got a calliper and the measurement of the nut (insidemost diameter, including the thread) it's 0.2 inches, or 5mm - I can't decide which measurement is the correct one as they're very close to each other. The bolt will need to be 40mm long excluding the head.

How do I figure out what size bolt do I need? As far as I'm aware, the bolt size includes the thread of the bolt, so the bolt will obviously be bigger than 5mm or 0.2 inches, not sure how I can measure the depth of the nut thread.

Any help would be much appreciated!

 

[Trazor]

5 m/m bore would be M6 thread.

 

[big-all]

if you have a hardware shop engineering place even a garage or motoring shop should be able to tell you the thread pitch/thickness and type if you take a nut
or is it a specialist bolt for furniture ??
a picture or link may help

 

[merlin50]

if the bolts are metric they will be 6mm

 

[oilboffin]

Measure across the nut flats 10mmacross flats is 6mm 13mm is 8mm 17 is 10mm and 19 is 12 mm

 

[maltaron]

Bear in mind that the bolts may not be metric, going by your measured size they may be 1/4 BSW or BSF. If you can find a friendly engineering works they may sell or lend you a selection of bolts to try and determune the thread.