Metal is not as hard as it lookes or feels. It is always moving. As the temperature goes up metal expands. As the temperature goes down it shrinks.This has advantages and disadvantages. The disadvantage? This changing of size can loosen nuts and bolts. The advantage? It can help us take things apart. An example would be wheel bearings. Most are in an aluminum hub. aluminum expands a lot when heated. So just break out the torch and have at it .. right?
You want to start with gentle heat and if nessesary go up from there. I use a hot air gun. Hair driers don't put out enough heat and boiling water...well..not me. You want to heat the entire object. IF you heat only one part of it whatever it is you are heating can warp out of shape... not good... so move the gun around to evenly heat it.
There seems to be a "magic" temperature(around 250 to 275 degrees). If you moisten your finger and lightly touch it to the hot part you will feel the moisture boil! Yes I really do this, and it does not burn me because I do it very fast ! It can burn you. If you want, try dropping a little drop of water on the part and if it boils off your there. At this temperature bearings will sometimes fall out of crankcases all by themselves or with just a little help. Not only that, the new bearing will usually drop right in if it's been in a freezer for an hour or so.
Notice I use words like "usually" and "might" and "probably" and the like. that is because this level of heat almost always works... almost but not always. Sometimes you have to go to the next level of heat. This would be a propane torch. Very gross but sometimes you have to use it. Remember if you get a part too hot you can take the temper out of the steel making it too soft...Not good. Speaking of tempering, if you heat a solid copper head gasket red hot and then quickly quinch it in water it will retemper it good as new. Won't work on steel head gaskets.
