UNC equivalent thread size?

[gasmansteve]

Hi all
Apologise if the wrong place to post this but the wooden geared clock I`m making needs some 8-32 grub screws (which I gather is UNC thread) these are proving a little difficult to get and I wondered what their metric equvalents are? I need 3 grub screws 8-32 x3/16 and 2 grub screws 8-32x1/8 anyone point me in the right direction please?
Cheers
Steve

 

[chrispuzzle]

I would try these guys

http://www.modelfixings.co.uk/steel_gru ... NC%20grubs

How are you tapping the threads? You might be able to use 3/16th screws of a different thread - eg BS Whitworth or UNF - if you are doing the tapping yourself.

 

[jasonB]

8-32 has a major diameter of 0.164" (4.16mm) so you could get away with M4 grub screws which will be easier to get the taps for and they will be of more use in the future.

Modelfixings is a good site to get either size grub screw from.

Jason

 

[gasmansteve]

How are you tapping the threads?

Thanks for the info Chris and Jason.
The grub screws will be `self tapping` themselves into birch ply! Yes I did wonder about that myself but the instructions that came to make the clock assure us that using soap as a lubricant it can be done. The grub screws are to tighten onto a brass spindle going through the birch ply gear wheels. I`ll post pics as and when I get there 8) I`m not really sure they have to be UNC to do that job but I`m keeping as close as poss to the plans. Very American based and all dimensions imperial but very interesting
Regards
Steve

 

[chrispuzzle]

How are you tapping the threads?

Thanks for the info Chris and Jason.
The grub screws will be `self tapping` themselves into birch ply! Yes I did wonder about that myself but the instructions that came to make the clock assure us that using soap as a lubricant it can be done. The grub screws are to tighten onto a brass spindle going through the birch ply gear wheels. I`ll post pics as and when I get there 8) I`m not really sure they have to be UNC to do that job but I`m keeping as close as poss to the plans. Very American based and all dimensions imperial but very interesting
Regards
Steve

If they are self-tapping then the closest M4 is going to be fine, I'm sure. It's not like the screw is there to do anything more than grip the shaft firmly enough.

 

[jasonB]

As the UNC ones are available I would go with them for this application as the thread is a bit coarser it should bite into the ply a bit deeper 32tpi v. 36tpi (0.7mm) for the M4.

Order a suitable hex key at the same time

Jason

 

[gasmansteve]

Bu$$er just ordered them and forgot the hex key :? Never mind I might have an Allen key that will fit !.
When I said the grub screw tightens onto a brass spindle it actually tightens onto a small leather plug in the hole which then pushes onto the spindle I think acting as some sort of slipping clutch allowing the wheel to be turned without throwing out the rest of the mechanism.
Thanks again
Steve