Interference fit

[tornitore45]

The issue was NOT dimension changing after a heat/cool cycle. W1 steel grows a bit after hardening. If a heat cycle changes the crystal structure, we are not dealing with a simple thermal expansion phenomenon.
The issue is about NON uniform heating.
Uniform heating, like in an oven for a long time to stabilize "grows" all dimensions. Holes get bigger.
NON uniform heating, like localized heating has no specific rules. It depends on the shape, the metal and the temperature distribution.

Heating the surrounding area of a hole in the middle of a large piece of metal expand the hotter metal but leaves the far away metal cooler and unchanged.
Where is the expanded metal going? Into the hole, making it smaller.

Is not hard to believe that somebody unaware of the problem and in a hurry may tend to heat the part near the hole and neglect to make sure the entire part is heated uniformly only to find out the hole has shrunk.

[Bill Shields]

suspect a bit of both with the bore changing permanently after a heat cycle and the duplex stainless....but then what do I know...just a dumb mech engineer trying to get a job one out in the middle of the desert with the tools available.

[Mr Ron]

If you reach the limits of heat/cooling to affect a press fit, how do you do the reverse, remove a press fit? Like how to remove a tire from a drive wheel without destroying the wheel. Applying heat to the tire would transfer heat to the wheel and prevent the tire from being removed. In some cases, the tire could be removed by machining, but this would not be done on a large diameter wheel like a locomotive wheel. I guess the tire could be cut through with an abrasive wheel in which case, the tire would "spring" open or be pried apart. Not knowing how its done, this is the way I as an amateur would do it.

[Bill Shields]

Getting a tire off is easy..chuck it in a lathe and turn baby turn.

On full size locos...grinder with cutting wheel and chisel get things off in a hurry.

Pushing an axle off is just lotsa pressure in the correct direction... however it always pays to check the mating surfaces before considering pressing back on.

This is where loctite had its benefits. 400F in the oven and everything falls apart.

[Mr Ron]

This is where loctite had its benefits. 400F in the oven and everything falls apart.

Are you saying full size railroads use loctite for tires?

[Bill Shields]

No....tires are all shrunk on

[neanderman]

Are you saying full size railroads use loctite for tires?

Good one. That's a lot of Loctite...