Radius arm question

[Colin D Smith]

Hello again chaps
Could anyone tell me the thread on the radius arm? I think that it needs a little tidy up with a dia, as the nut only go's on around one turn. Maybe a run through the nut with a tap while I'm at it .. Early arm..

[Ruairidh Dunford]

5/8” x 16 tpi

[Colin D Smith]

Would that be unc? Sorry I'm just a little slow.

[Steve Jones]

No, Colin. It's an 'Admiralty' thread. Used on half shafts, crank shafts and radius arms. Dies and taps are available.

Steve

[Colin D Smith]

Thanks guys . Will have a look

[Ruairidh Dunford]

Sorry - I did not make that clear, as Steve says, special thread.

A7 Components (David Cochrane), sell taps and dies.

[JonE]

just check it hasn't already been run over with a die that wasn't the right one! I found one arm that was odd and seem to remember finding that there was a close tpi that might have been used. Sorry can't remember more.

[Martin Prior]

We've been looking at the radius arms from my grandson Henry's 1938 Ruby. A previous owner had hit them so hard when removing them that the threads, instead of being 5/8" x 16tpi, are now 3/4" x 22tpi. This is going to be a challenge!

[Colin D Smith]

Hi chaps. I spent around 5 hours with a needle file and managed to get the nut to go on.   pwee!

[squeak]

Martin would an annular broach drill of the right internal diameter bring your thread back to size? Followed of course by a die, the engineers amongst us are invited to say why this is a ridiculous idea. My parachute is at the ready .