How would you tackle adapting a 19.9mm pulley bore to a 19mm shaft?

[dave h 2]

All I would do is turn up a sleeve to fit the pulley with a hole of around 16mm. So that's 19.9 od and 16mm id
Mount the pulley on the lathe and get the hole to run concentric.
Glue it into the pulley bore with JB weld. You can't press fit as you are about to file the keyway out of it.
The next day bore the pulley gently out to 19mm.
File out the 0.45mm thick bit covering the keyway.
Hopefully the pulley bore is 19.9mm round and not oval.

 

[Brad93]

Another option is build up the internal bore of the pulley with an epoxy compound like Belzona 1111, Resimac 101 or Devcon.

This is readily machined.

You can use a 17mm diameter former coated in release compound. As long as the former is centred you'll have a mm either side to machine out.

What size is the keyway, if you want to post it down i have lots of broaches i'd happily do it for you.
In fact i have some belzona too.

 

[Rannsachair]

Thanks for all the suggestions folks.

When I looked at the clutch relative to the shaft I realise that the clutch is longer than the shaft and the key is about half the length of the keyway.

So decided to try a sleeve not the full length of the clutch.

So on with the 4 jaw to true up the clutch body:

and bored out shaft:

horrible zinc alloy material.

Then turned a length of aluminium:

drilled and bored then milled a partial keyway on the wee Centec 2A:

The key will still engage in the oversized shaft bore, though hopefully be reasonably retained by the sleeve:

Pressed the sleeve into the clutch and had a run through with an expanding reamer to clean up any distortion.

Finally retapped the M8 thread in the shaft and refitted, seems ok:

Takes an age cleaning up all the aluminium swarf, another job done.