I'm currently working on a project and a machined screw has been misplaced... It's a tiny little thing and since it was built in the 1920's I highly doubt it's going to be a standard B&Q job! So, does anyone know of a tool I can pick up that I could screw into the hole to determine the screw size I'd need to get to find a replacement? I've spent all day finding screws around the house from various objects but none seem to take!
Tool to determine screw details from hole
- Thread starter marc11657
- Start date
Help Support GroupDIY Audio Forum:
I don't know how accurate for very small holes, my old calipers have the capability of measuring hole diameter but for holes that small they may not sit square in the hole so could be inaccurate.
Why not buy a few of the smallest screws you can find and try them?
JR
Why not buy a few of the smallest screws you can find and try them?
JR
a conic point, a piece off rubber or tape, a caliper, you put the conic shape in the hole, put something at the out side that matches the surface and stick to the cone, then measure with the caliper the cone touching the mark, not as precise but a number to start working, screw will be bigger because you would be measuring the inner of the tap.
JS
JS
Where was the equipment manufactured? Imperial or Metric is the usual choice. Pray it's not BAE.
I don't know how familiar you are with sizing screws. Imperial screws come in number sizes. A #4 is just under an 1/8". A higher number is a larger diameter. All American screws share the number designation. There are two thread types. N.C. and N.F. Coarse and fine thread.
A #4 screw comes in 4/40 and 4/48. The second number is threads per inch. 4/40 is the N.C and 4/48 is N.F. With metric I think the screw size is tied to the thread pitch but I'm not as familiar with metric hardware.
With a little trial and error and an assortment of screws you can figure it out.
I don't know how familiar you are with sizing screws. Imperial screws come in number sizes. A #4 is just under an 1/8". A higher number is a larger diameter. All American screws share the number designation. There are two thread types. N.C. and N.F. Coarse and fine thread.
A #4 screw comes in 4/40 and 4/48. The second number is threads per inch. 4/40 is the N.C and 4/48 is N.F. With metric I think the screw size is tied to the thread pitch but I'm not as familiar with metric hardware.
With a little trial and error and an assortment of screws you can figure it out.
firehazard
Active member
Hi,
if the B+Q reference means you are in the UK then a BA (British Association) thread is quite possible.
These are related to metric threads but only a few will be interchangeable.
You need to accurately determine how far the thread goes in along its axis for one full rotation. Calipers are OK but I would use a dial gauge or "clock" as they are often called.
A matchstick shaved down to a size that follows the thread but doesn't run the risk of getting stuck would work.
This will give you the pitch of your female thread. If you get the matchstick just right you should be able to estimate the outside diameter with a reasonable degree of accuracy. With these numbers you can look in the charts for the closest equivalent.
As has been pointed out, there are a bewildering variety of thread forms. For something as old as 1920 it may well be a non standard form. Especially if european.
What is it you're working on?
I have a selection of BA screwcutting gear and instrument makers lathes if you can get accurate measurements. Any clockmakers nearby that you can consult?
The alternative is to recut the thread for a screw you can buy.
Take care..
if the B+Q reference means you are in the UK then a BA (British Association) thread is quite possible.
These are related to metric threads but only a few will be interchangeable.
You need to accurately determine how far the thread goes in along its axis for one full rotation. Calipers are OK but I would use a dial gauge or "clock" as they are often called.
A matchstick shaved down to a size that follows the thread but doesn't run the risk of getting stuck would work.
This will give you the pitch of your female thread. If you get the matchstick just right you should be able to estimate the outside diameter with a reasonable degree of accuracy. With these numbers you can look in the charts for the closest equivalent.
As has been pointed out, there are a bewildering variety of thread forms. For something as old as 1920 it may well be a non standard form. Especially if european.
What is it you're working on?
I have a selection of BA screwcutting gear and instrument makers lathes if you can get accurate measurements. Any clockmakers nearby that you can consult?
The alternative is to recut the thread for a screw you can buy.
Take care..
