Cracked Ml7 clutch pulley casting

Hi everyone, I have have an ml7 clutch but it had I little wobble and was producing a slight knocking sound. A strip down revealed that the casting of the pulley has cracked creating play on the spindle. Does anyone have any suggestions on the best way to fix this? I have thought about machining the cracked bit away and then sleeving back to original length it but this would mean the casting would be reduce to about half an inch deep, not sure if this is enough.

I also thought about put a sleeve around the outside but as you can see not much room to still leave clearance on the springs.

Im pretty new to lathe work so neeeding a bit of guidance.

Paul

Hello, Paul

That's not a pretty sight

Looking at your first picture ... It may be possible to machine away the whole of the 'bearing' and face that little flat area; then make a tube with a flange to register against it.

Not knowing how much clearance there is around it; this is just 'food for thought'

MichaelG.

Welcome aboard Paul

is it cast iron or alloy?

Either way the best solution might be to open up the crack and get an expert to fill it with weld before re-boring.

Neil

Hi Paul, bad luck. I think I would shrink a sleeve onto it, with a relieved area for the springs to fit into. If you thoroughly clean out the crack with brake cleaner spray, Machine the sleeve for a slightly tighter than standard interference fit, say .0015" to .002" smaller than the outside diameter, then heat to red heat and drop it on, it should close the crack up. Having said that, this is not a job for the faint hearted. The problem is the part has opened out where the crack is, and is now bell mouthed, and unless you can get it closed up again it will still wobble. You could set too and make another clutch housing in steel, but steel does not have the same coefficient of friction as cast iron, so it may be a bit too slippery. Could you not get a spare part, or is it horrifically expensive (as usual) If you could get a bit of cast you could machine one up....................if you had a lathe that worked that is. It looks very much like the brake mechanism on my Colchester Mk1 roundhead.

Phil

This will be in cast iron and the worry with welding is the concentrated local heating risking further stress crack propagation. It could be preheated as a whole beforehand, followed by very slow cooling

I think though there is room enough away from the clutch springs to shrink a thin walled sleeve in high tensile steel over it, that might be a better alternative. I have seen a socket rescued in that way, it still worked with a three foot bar on it to torque up bolts on a silage cutting machine in the middle of harvesting.

Brian

Phil. You just beat me to it! 

Edited By Brian Wood on 23/01/2016 17:11:43

Thanks for all the replies!

Yes it is cast iron, I've heard it's not handy to weld. As far as spares go myford don't have anything for this clutch , and eBay just have the whole units for about £200. I think I would prefer to do a vfd conversion than buy an other clutch unit. I still have the normal pulley so can use that in the mean time.

The outside sleeve seems a good idea to do first, if it doesn't hold at least I can still try Michaels idea too. I am currently replacing the headstock bearings and spindle which isnt as handy as I first thought it might but hope to get that sorted next week then I can get stuck into this

Take dimensions off the damage area for reference.

Machine it off and bore through the pully to the outer diameter of the spigot.

Turn a new spigot to the external diameter 0r the cast shoulder to register against the shoulder.

Turn one end down to be an interference fit in fit in the pully and press in, you might also want to use a bit of locktight. You could drill a pin hole the other side on the diameter line and drop in a pin to stop it spinning under load.

Remount in the chuck and set running true and drill and bore to the correct internal diameter. Then face to length. Don't forget to re-drill the lubrication hole if that is what they are.

Turn the o/d to allow for clearance on the springs.

Edited By Bodgit Fixit and Run on 23/01/2016 18:37:00

Why do Myford's need clutches, how many hobby size lathe can you find, belt head, back geared, with a clutch. my 13 x 26 Taiwanese BH BG lathe has been going over twenty years with out a clutch with no harm to the motor.

Ian S C

Oxy-acetylene welding of cast iron is not difficult. Use cast iron rod and borax flux. The real issue is to prevent hardening from rapid cooling. You need to preheat the casting to about 800F before welding. After welding you need a very slow cool.

Hello John,

Is that temperature Fahrenheit or Centigrade? 800 F doesn't feel high enough. I have always felt happier doing such repairs to cast iron with Sif Bronze which takes readily to C I. Again, always with preheating and very slow cooling.

Brian

If I were doing ths job I'd use Bodgits method of boring out and replacing the sleeve, possibly use bronze for it as you now have a choice of material.

I would not weld onto the cast iron, even though I'm quite good at it as it raises all sorts of problems, further cracking, hard spots etc.

TBH with a piece of material to hand the whole operation would only be a 1/2hour job, far quicker and guaranteed to work.

On reflection, both Bodgit and JS speak wisely, a suitable piece of cored bronze would be entirely suitable for the job

Brian

.

Ahem

May I claim priority ? ... even if my description was not fully detailed.

MichaelG.

Another idea, is to make the full diameter sleeve with a threaded portion on the end, thread right or left handed to best suit self tightening. Bore pulley and create internal thread to suit sleeve. Loctite in for added security.

You may indeed MichchaelG. I hadn't connected you had already suggested it.

Yes it will weld or braze, but the point is the OP says it wobbles, so if you don't close the crack up, it will still be bellmouthed, and will still wobble. Welding or brazing will make sure that the crack never closes up. If you sleeved it, it wouldnt need welding or brazing