Assembly Problem "1"

Will this be part of an over unity machine? Something to do with magnets, perhaps?

This appears straightforward. You could do it with a pair of pliers. What's the problem?

Can you provide dimensional drawings of the tubes?

It sounds like you want to limit the distance the aluminum tube extends into the steel tube before it becomes a permanent fit. Take a piece of aluminum and form a clamp out of it that fits around the aluminum tube. After the steel tube cools and is fixed, you can remove the clamp. The steel sleeve will be handled by tongs and a piece of wood can be use to press it unto the aluminum tube.

An arbor press might do this; failing that, a hydraulic press. In addition to heating the steel, you could chill the aluminum with dry ice.

Expanding on RedFred's suggestion-

Make a table of wood with two plies- top ply has a hole just larger than steel tube, lower ply is solid. Upper part of the assembly is another piece of wood matching top ply that will just hold the steel tube.

Induction heater "wraps" around steel tube- between the wood plates with holes.

Second set of wood plates and spacer rods sits on top of assembly holding steel rod and induction heater that holds aluminum tube.

When IR heat sensor determines that steel tube is hot enough, induction heater stops and upper assembly repositions and drops aluminum tube down into steel tube and fan unit starts to cool steel tube.

When IR heat sensor determines that steel is cool enough, upper assembly pulls bask and electromagnet is lowered to lock onto steel tube (with aluminum core) and lifts it out of upper hole.

Then electromagnet lowers next steel tube into position, releases it and cycle starts again with new aluminum tube manually inserted into upper assembly.

I agree, no detail on the length of the parts, or insertion depth. Drawings would have been nice.

Your design is a reversal of conventional shrink fit where the highest expansion material is on the outside and produces compression as it cools. You will have to design your interference so that you maintain sufficient compression at the LOWEST use temperature. You will also need to assemble the two parts quickly, before the aluminum tube gets hot.

I thank all the participants to my query, and very special thanks to REDFRED and ENERGYGOD, who began to develop practical ideas how to design and construct such an assembly gig. Indeed we will use Induction Heating. Thanks to TORNADO for the dry ice suggestion. For rapid cooling of parts, common industrial practice these days is dipping the part in liquid nitrogen... the effect is almost immediate and the temperature is as low as it gets. Almost. Again, my thanks and appreciation. AMB.

Glad to be of some assistance- good luck on your project.

Would liquid nitrogen make the aluminum so brittle that it would shatter?

It sure could shatter. So don't hit it.

Are there springs, flat washers and paper wadding involved here?