Radius arm question

[Martin Prior]

A broach drill is an interesting idea.  I must look into that.

[John Cornforth]

I highly recommend getting a thread restoring file. Usually cover 8 different sizes, get an imperial one (whole numbers of threads per inch).

[Bob Culver]

Er... what is a broach drill pse?

A neat fitting sleeve with a protruding one side flat threaded hard tooth can be wound off and on to improve a thread, but unless have some suitable tube requires a lathe. Old ball race rings softened provide handy sleeves for a variety of uses..

Incidentally where a die is possessed the old style two piece dies are much superior for restoring threads as can be started on.

[Martin Prior]

Thanks for the suggestion, John.  Unfortunately, having spent about £35 on a thread file the bloody thing was blunt within five minutes!

[squeak]

Bob it's a very fast hole cutter leaving a centre plug which is ejected. It may have a self centering effect when used on the end of a radius arm in a vise. There may be internal clearance issues causing it to bind.

Google is your friend, I have been unable to paste a picture, sorry

[Martin Prior]

To return to Squeak's suggestion of a broach drill, I assume that we're talking about something like the items in the photo(?).

   

I'd need to check the internal diameter with the supplier, but I guess that it wouldn't be the end of the world if it wasn't exactly 5/8" - I could re-thread to the nearest available size, I suppose.

The major practical issue would be setting the radius arm accurately.  I'm wondering whether I could fix them rigidly to the lathe cross-slide and hold the broach drill in the chuck.

Better ideas would be welcome!

[Hedd_Jones]

Martin

I had to do one of these manually once. Its on the grey car here

I got my mate to build up the area where the threads went with weld, he ground most of the existing threads away before he built it up. We didnt touch the plain portion that goes in the axle.

Once home I annealed the weld, warmed it up orange and let it cool slowly in some lime.

Then ground/filed it back round 5/8. I put a BSF thread on it (14TPI I seem to remember from memory) as I had tooling. Then just cut down a BSF nut to suit.

[Howard Wright]

Hi All

When my RK arrived from Sweden where it had resided all of its life the radius arms had been turned down and threaded M14.  I guess BSF or admiralty threads were a little difficult to find in Sweden!

Doesn’t seem to have caused any problems.  Might if the car was subject to competition (trials) use?

Cheers

Howard

[Martin Prior]

Realistically, I think that I'll probably have to go down Hedd's route.  Very tedious, but as long as I can file the ends to a uniform diameter we should get there eventually!

[Bob Culver]

Assuming the dia has to be reduced for some reason, a broach drill is overkill in the extreme unless chance to have one. Often quicker to sort by hand but if mounted on a lathe saddle a tube in the chuck with an internal protruing threaded siver steel  tooth can be used to reduce dia and cut a thread, or the beginnings of one.
The pre Girling type have to be done up tight or rotate themselves. There is  scope for a dowell or grubscrew somewhere to prevent rotation and then any alternative nut or set screw, or stud and nut,  does not have to be extremely tight.