How do I take up the slack in assembly

[John Hill]

I have made great progress on my Monster Stepper project (which is part of my CNC router table) but I have a large worm to mount on a shaft.  The bore should be 5/8th but it is somewhat worn and is a loose fit on the shaft,  normally I would knurl the shaft  a little and use Locktite the theory being the knurling would help to maintain centrality but this is a stainless steel shaft which I assume would quickly work harden and destroy my knurls.

 Any ideas?

[John Rudd]

Could you build up the stainless to diameter with silver solder?

[bertie_bassett]

can you bore out the worm at all or is it to hard?

if it can be bored out, then just sleeve the shaft to suit.

otherwise, would an epoxy metal be any good to redo the bore with?

[tekfab]

Not all stainless steel work hardens and look at it this way what does a set of knurls cost against the time in finishing the job and how many attempts at finding a suitable alternative ? and as i said not all types of stainless work harden so . . . . . . . .

Mike

[sparky961]

Don't suppose you have access to a TIG welder, eh?  Or even MIG with stainless wire (but you wouldn't have near the control that TIG affords).  Alternatively it may be possible to turn down a section of the rod and make a press fit sleeve or two-part sleeve if you don't have access from an end.

One more suggestion if you're just trying to get a tighter fit without a big production, use a hammer and punch with a shape of your choosing to displace metal and make for a tighter fit.  Depending how much slop we're talking here, you could even turn it concentric after beating the hell out of it for a bit.  Maybe centre drill it first...

[steampunkpete]

Um, how would the bore of this worm gear wear exactly? I've seen a very small number of applications where a worm has rotated on a shaft (as opposed to rotated with a shaft) but they all were configured with the worm made as one part with a pinion. (This is another thread where pictures would help).

Are you trying to fit a worm with a metric bore onto an imperial shaft of a close size? (or vice versa)

You could spend a long time on this and end up with a ruined part or concentricity issues. A worn bore would suggest the worm thread could be worn, so more backlash that you would like.

 For all the time and trouble I'd be tempted to carefully measure up and get a new worm.

[John Hill]

Dont fret, the worm came on a shaft with a matching gear wheel in one assembly along with a clutch to disengage the work from its shaft,  it also came caked with lanolin and wool fibres and is quite likely a relic of the long gone textile industry in this town.  For all I know the worm spent all its working life with the shaft turning, the worm and wheel stationery and the clutch being engaged infrequently.

No, I will not be buying a new worm, if I went down that route I might as well buy the entire CNC router table and spend the time I saved polishing my workshop equipment instead of using it!

[petertheterrible]

1 How about shimming it?

(If it's not a customers project.)

2 Or a double cats claw.

(Six tapped holes and grub screws)

3 Or a male to female stress relief.

(Male one side, female the other to take the parts with spiral cut to protect the steppers when overburdened.)

[John Hill]

Thanks Peter, some good ideas there, this is my home shop project to build a router table.

I am going to chuck the worm today and see if any of my lathe tools can work the metal,  files just bounce off.

[vtsteam]

If they can't bore it, and it's heat treated steel, John, you can probably anneal it, bore, then re-heat, plunge, and temper to whatever color you prefer.

[John Hill]

I got smart and went and borrowed a better knurling tool     The worm is now a press fit on the shaft and I hope as true as any other method I might have tried.

Thanks for all the suggestion.  Incidently, even though the worm felt loose on the shaft it took only a very shallow knurl to snug it up.