Club 80-90 Forums

Need to make a loose key-way pin captive in the key-way of a motor shaft ....
Its been done before with a very small cap head bolt tapped into the shaft but that's snapped
So my quick fix is to try and get a couple of weld spots on it and then dress them down to fit
The shaft is a loose fit into a drive pulley assembly for a spindle moulder....
So to the question ....
Will the shaft get too hot and ruin the motor in the welding process
Andy

I would have thought that you will create more problems than you solve - you will kill the temper in the shaft leading to the possibility of bending it , especially with the weight of that cast iron pulley throbbing on the end of your shaft.
I would make a new key from a sheet of mild steel - I wouldn't use anything else otherwise when you hit a really nasty knot you haven't got the ability for the key to shear (saving the expensive motor).Then if the pulley is loose on the shaft use some shimming brass sheet to give a tighter fit
Failing that you could just give the spindle moulder to me, I was going to buy one 20 years ago and never did!
E D I T
It might be easier to get a new alloy pulley that is a tighter fit.

Cheers but think the design is such that there is no weight imparted onto the shaft as the pulley and bearings are on a separate flange (the white one) which then clamps to the end of the motor....
The whole system resembles a one toothed cog driving system
Flat belt drive system would likely slip if things got bogged down
All you said was valued input thank you.

By the way its a Lurem Junior machine.....

Andy

I would also make up a new key but use key steel rather mild steel, have some here depending on the size and as OBG says shim or loctite it in place, or perhaps both. Would not put welding heat near a motor shaft for several reasons.
You could also drill the pulley and tap it so that the lockscrew presses against the key, holding it into the keyway, thats what I did on one of my vertical milling machines when it kept giving me probs.

i was given a small pillar drill about 15 years ago because of this problem!

tried sourcing a key to no avail so i welded it!

been fine ever since and its been worked hard!

depends how good you can weld/the quality of the welder and when welded get the airline blower on it to cool it. will need alot of heat to damage the item.

Do it, don't do it. Conflicting advice here. If it were me I'd use some kind of heat sink to minimise heat damage (big pair of mole grips further down?) and go for it. If you've got little to lose in trying then give it a go but do it in short bursts and allow to cool in between. Be better if motor was stripped, particularly if there are plastic/nylon parts nearby.

Far better though to find yourself a local lathe man, get the shaft trued up and have him make you a pulley to fit that. I do know a guy in Cov that could probably sort this for you. But must be a garden-shed engineer local to you that could help you.

Dont know if a pair of grips would be a good enough heat sink. Depending on tha shaft diameter the heat might cause distortion, or as you say damage internal parts on the motor, possibly the insulation of the windings, if the screw broke inside the keyway it would need milling not turning. Truing a shaft like that would have to be done using high speed steel tooling not carbide because carbide would not like the interrupted cut of the keyway and it would probably chip the tool. dont see why the key needs to be welded anyway, Got lots of machines here that do heavier work than that and they all have loose keys on shafts.

There appears to be two problems:
1. the keyway is open at the end.
2. the pulley is a sloppy fit.
Fixing 2 with shimming brass will stop chatter on the key which might be why it is failing and possibly place more pressure on the key holding it in place.Making a new key would sort that.
Is there a thread in the end of the shaft that would take a bolt and washer to prevent the key from exiting?

If you keep your spot welds short in time you will have no problems.
Done myself on a starter motor for an old Italian bike that I once had.

That was my reasoning too

It might be easier to get a new alloy pulley that is a tighter fit.

That, or as oldiebutgoodie says, steel or brass shimstock, and then a drive fit (heat pulley, ensure inner end of hole has a slight chamfer).
OR... A good lathe turner could bore out the existing pulley and make a tight int. fit bush in fairly short order, again, shrink it in.

I think I would also try to get a better fitting key made, or sourced, but from good key-stock or at least 3/4 hard steel plate

I would also definitely use Loctite Bearing fit, once the tolerance is down below about 10 thou, it starts to work like a weld anyway

I would not weld it initially, the mechanical option gives you that final method if it does then fail. The motor components look very close to the weld area. (If you do weld, use Cold Front packed a round the shaft below it)

===

Methinks the present (damaged) retaining screw thread one size too small!

Anoher way to solve that problem providing you can see both slots from the end when assembled is to ditch the rectangular slots by drilling down them when assembled then using a round key instead. If you make it a good tight fit it will also accomodate your slack bore to some extent. I have seen this method extended by tapping the hole and fitting an allen grub screw.
Cheers
Bodger Wolfie

We will get this machine fixed somehow!

Not ignoring you folks but at this moment in time I am trying to establish as to whether the shaft is supposed to be loose fit into the pulley casting or if it has previously sheared and spun wearing the shaft down ,mind you the hole through the pulley is nice and tidy still

The end of the shaft is tapped out but the previous (snapped &as big as it`ll take) cap head repair is blocking the hole

Andy

HSO Cobalt bit drill-out then? Nasty, they're tough boogers, try a 3mm starter?