I work for a bearing manufacturer. The reason a specialized bearing heater is used to install press fit races is because too much heat from home made heating can take the temper out of the metal, drastically reducing bearing life.

When I say home made heating, this usually refers to people who use torches to heat the part, which I've seen. Using a hot plate or coffee maker sounds fine with me as long as the installer is mindful of not overheating the part. For a DIYer who only needs to install races occassionally, this sounds like a good method instead of buying specialized equipment to clutter up the garage.

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95 E320 Cabriolet, 159K