Interference fit

[dereklola]

I'm making new alternator pulleys - aluminum centers inside steel micro-V rims - similar to those in attached pic. I'm making the centers, bought micro-V pullies and will machine out the middle bit leaving just the rim.

What interference fit should I use? .001....002.... other?

[R. Pare]

That would depend on the rpms and the torque the pulley will have to deliver.Without knowing any of that, though, at the minimum i would go for .001"-.0015" per inch of diameter. I would also look for a way to key it, even with only a .125" dowel on edge.

How are you planning on keeping the sheave from eventually walking off of the aluminium center?

[dereklola]

Richard - thanks - I knew there'd be more questions!

However your guidance helps and is in the ball park I was expecting - if you'd said anything wildly different I'd be scratching my head.

As for the outer walking off the inner over time - all I can say right now is the ones you see in the picture are ones I made five years ago (and which you saw at Indy 3 years ago) and they haven't moved at all.

If it turns out my interference fit is insufficient I will either make a new center with a bit more interference or use your idea of a radial dowel 'key' - I presume you mean inserted radially when you say 'on edge'.

Thx - Derek

[Matt Clark]

as a suggestion to help with the question Richard mentioned about keeping it from walking off... here at work, we often drill & tap a hole thru the mating diameter, parallel with the shaft axis, then either threadlock a setscrew or a bolt that gets machined off.