identifying a screw thread

[JohnD]

I have some sliding, mirrored wardrobe doors, probably 30 years old. The weight is taken by wheels running in a floor track, and at the top they have a sliding carrier that keeps them upright running a white plastic rectangular slider in another track, with a spring to keep the carrier tensed against the track. This carrier is in pressed steel and is held to the channel frame of the door using a screw. The hole in the carrier has a couple of turns of thread on it to take the screw.

Two of these screws have got lost during building alterations. I tried a metric screw in the hole, a 4mm screw will not quite go in. I still have 4 of these screws.

Any guesses what the thread might be that I should try to get?

 

[merlin50]

is it a corse or fine thread

 

[JohnD]

fine thread

thanks for your interest

looks like we have just found the missing screws though

 

[wingcoax]

If english, at that age it could be 4ba. It is slightly smaller than m4 and most good hardware shops (not sheds) should have some in stock.

 

[merlin50]

good that you have found them, they may be UNF

 

[TicklyT]

http://www.tapdie.com/html/tapping_drills_for_taps.html has some useful info.
'BA' sizes used to be common on anything smaller than about 3/16".

 

[tonyelectric]

As others have said probably BA, there is a shop in Salisbury (see you are in Hampshire, so not too far away) called Pennyfarthing Tools, they keep all the old imperial threads and also have thread guages so if you take in the bolt or nut they will measure its outer diameter and TPI to ensure you get the right size.

 

[mattylad]

Out of interest, were these Stanley sliding doors?