press fit aluminium in to cast iron?

[smashweld]

I have a few change gears for the lathe with too large a bore, I have some alu bar that I'm hoping will be fine to use, it's just round bar bought from Aalco so not sure exactly what grade it is

I've read .001" per inch of diameter is a good guide, does that seem reasonable for aluminium to cast iron, the plug/insert will need to be about 1.25 inch diameter

any problems with those materials/sizes?

 

[RWD3M]

Only problem I can think of is dissimilar metal (galvanic?) corrosion

 

[Guineafowl]

You might find that the press fit will reduce the ID, so either compensate for that or ream them out afterwards.

A safer way would be to make the bushes a thou or two undersize (OD), check fit and bond in with loctite 648.

 

[smashweld]

hmm, I've got one 'made' but now u mention it would prob be easier doing the boring out and doing the keyway once it's pressed in

 

[Chippie]

Unless the gears are being driven via a key way on the bore, I’d just make a push fit sleeve…( that is where two gears share the same shaft, with one gear driving the other via the key) .the gears on my lathe that are driven in such a fashion, sit on a sleeve with a key on the outer dia. and just push fit into the bore of the gear which has a matching key way cut in it..

 

[Morrisman]

Put the bushes in a freezer overnight before you press them in, then they'll expand in place and be nice and tight.
You could even do an experiment, accurately measure a piece of ally before and after freezing, see how much smaller it gets.

 

[smashweld]

Unless the gears are being driven via a key way on the bore, I’d just make a push fit sleeve…( that is where two gears share the same shaft, with one gear driving the other via the key) .the gears on my lathe that are driven in such a fashion, sit on a sleeve with a key on the outer dia. and just push fit into the bore of the gear which has a matching key way cut in it..

sorry I don't really understand...the shaft has the key and the keyway in the gears...a pic below

how is the sleeve attached to the shaft on yours?

 

[Chippie]

See the photos….

 

[smashweld]

Ah, I see, yeah the gears are either directly driving or being driven by the shafts on mine...you can have 2 gears on each shaft but no sleeves

 

[smashweld]

using the lathe to cut the keyway...was a bit lax with the first couple of tries, messed up a few gears... ended up making a keyway 'tool' that I saw on a few Youtube vids, fair bit of time spent making sure it was square and to get it the proper height and it's all good now...was a bit stressful tbh!