Educating me - Interference fits

Is there a rule of thumb for the amount of interference by metal types and diameters for a press fit? I haven't managed to find one online.

For the cast iron bushings going into my throughhole in ally I turned them just over 2thou oversize for the 29.40 and 29.45mm holes in the ally block. I then made a spindle to their 24mm ID to keep them aligned for pressing.

Not having a press I planned on using the bench vice but since the 90mm block plus bushings was a tad long to fit I had little choice but whale on the end with a wooden mallet to get them seated such they'd go into the vice. They did press in but only with a pipe extension over the vice handle (which bent in the process). I'd expected to press into a soft alloy easily - for sure they're not going anywhere..

Sounds like you need to buy some basic engineering table books - Zeus tables for a start and Tubal Cains Model Engineers Handbook would give you just about all the info you'll need.

In your example you've got at least twice the interference you need. Since the block is aluminium you'd probably have been better using warming the block up until the bushes dropped in and then allowing the assembly to cool

For interference, about .001" per inch diameter, stick the aluminium in boiling water, and the cast iron in the freezer, there should be no problem with assembly. No press, get a big fat bolt, and heavy washers, and pull it through with that.

Ian S C

Lots of info on the net. Do a search for Limits and Fits.

Paul.

Thanks,

pgk