Union graduate bed attachment set screws

[bigbigblue]

As part of some modifications I am planning for my Union Graduate, I will need to source some longer set screws for attaching the bed to the headstock. The originals are listed in the parts explosion I could find as '1/2 inch x 1 1/2 inch set screw', no mention of the thread. It looks like it could be 1/2 inch Whitworth, but can anyone confirm what thread it actually is please?
Many thanks

 

[minilathe22]

Mine has 1/2" whitworth threads in the body. True Whitworth profile set screws can be expensive, so you can consider UNC bolts instead as they have the same pitch and will fit. Just maybe not as strong a hold due to the thread profile a little different.

 

[bigbigblue]

Thanks minilathe22. Indeed I was shocked when looking on eBay for Whitworth set screws. The cheapest I could find were nearly £6 for a pair of 2 inch set screws. I actually only need 1, so for £3 or so, I would rather have the right one.

 

[J-G]

Mine has 1/2" whitworth threads in the body. True Whitworth profile set screws can be expensive, so you can consider UNC bolts instead as they have the same pitch and will fit. Just maybe not as strong a hold due to the thread profile a little different.

WRONG !! - ½" UNC is 13tpi but ½" BSW is 12tpi

½" is the only size up to 2" where the pitch of BSW is not the same as UNC.

Also, the profile is more than a 'little' different -

UNC 60º, flat Crest/Root, 0.4411 - 0.4485" E/D​

BSW 55º, rounded Crest/Root 0.3932" - 0.4466" E/D​

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[bigbigblue]

I have ordered a couple of 1/2 inch Whitworth set screws. Thanks for the help.