[singleminded]

I forced my lathe into 3 tpi ish to do 2 fork spring ends, by the time i got to the full depth with a round cutter the belt was trying to slip..It was making a noise I would not want to repeat.
I had to do some internal threads for my finned exhaust nuts and i ended up turning the spindle by hand as well as they were only about 8 threads deep and i needed all the engagement i could get.
The reason for drilling the mainshafts was my thought for the future, but boy was I twitchy about doing that to a part i could not replace.. 

[clutchslip]

I take your point, I didn't realise it was such a coarse pitch, my lathe is 4tpi max. The strain on the change gears would be excessive to drive the leadscrew that geared up. I have heard of methods where one drives the leadscrew with a hand crank and the change gear train then drives back to the headstock but that would require a special gear train for that reduction. I often need to cut internal threads without a motor drive just hauling the chuck round with the key, backing off and winding out by hand too, it's a slow but reliable method, so turning the leadscrew with a hand crank, I could see working.
   
It's an interesting problem. If you ever do wear out a scroll it might be better, as you suggest, to convert to the clutch bridge type.  Kim

[singleminded]

Unless you have some sort of miracle lathe then something like 1tpi is impossible. It would be possible if I had a fully universal dividing head but I unfortunately😔 don't. I have thought about whether it would be possible to make it straight and then twist it to shape like they did with the BSA and Triumph triples.

[clutchslip]

Is the pull clutch scroll a multi start square or acme thead?
If so, it should be possible to screw cut, good that you can convert to the bridge clutch, would you use a clutch centre like mine?  Kim

[singleminded]

I have the pull clutch on my 9A and my 90. They work well but if the worm in the cover ever gives up the i will have problems. I have no idea hoew i could manage to machine that. so i took advice from Chris Odling and drilled the mainshaft of my spare gearbox and it turned out a treat, I can now change to the clutch bridge operation if i need to and may well do so anyway just to see if there is any difference..John

[clutchslip]

Made this castle nut socket out of a bit of EN16, haven't tried it yet but should do the biz on the clutch centre nut.

[clutchslip]

The clutch pushrod bush looks like it is a press fit into the shaft so as I see it the circlip should keep the bearing (which has to be loose in its housing so it's easy to extract to get at the nut) in full contact with the outer dia of the bush, I guess the bearing would creep forward without the original ring nut or my circlip?

[clutchslip]

Thanks John, I'm not really familiar with this clutch yet although it is more conventional than the pull clutch that my brother has in his Lion, I believe there is a shouldered sleeve that locates in the bearing bore that supports the clutch pushrod, will have to dig the box of bits out and have a look.
Our two Lions were passed down from our Dad who made a good one (my brother Daves 1932 model) out of the two so I've got a bit of a mix and match job, good fun though sorting it all out. Great having guys like you who know these bikes inside out and can answer our queries. Cheers Kim

[singleminded]

The plate that screwed into the centre to cover the bearing had a samll hole in it just big enough for the pushrod to go through..My mates bike has this clutch and we had problems with it but not as bad as yours . the earlier centre looks simoilare but does not have the outboard bearing or housing.  John

[clutchslip]

Been welding some new studs in my (1935) Lion clutch centre and a fix for what I imagine is a threaded lock ring for the bearing. As you can see the thread has been well abused and reclaiming it would not be easy so I have turned a circlip groove in the damaged thread and fitted a standard 32mm internal circlip. Appears to work ok so far. Can anyone foresee any problems with this mod? and what could have caused the thread damage in the first place, can't believe it was a hammer and chisel but it does look that way!