Friction drilling, also commonly known by the trademarked name Flowdrilling, is a non-machining method of making holes in metal, in which the material is melted by adding high pressure and friction energy.
Friction drilling is commonly used on bicycle frames, heat exchangers, and to create holes for mounting bearings.
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Already in 1923, the Frenchman Jean Claude de Valière tried making a tool that could make holes in metal by friction heat, instead of by machining. Then, it was only a moderate success, because at that time the right materials were not yet available. Moreover, he hadn't yet discovered the right shape for this kind of tool.
It was not before the 1980s that a useful tool could be produced.
Friction drilling uses a very heat resistant cemented carbide, pointed but not sharp object. This device is pressed against a target material with both high rotational speed and high pressure. That way, there is a high local production of heat so that it reaches the melting temperature of the object, making it plastic. The tool then "sinks" through the object, making a hole in it. Unlike drilling, material that is flowed is not lost but it forms a sleeve around the hole. The length of that sleeve is about 3 times the original thickness of the material.
There are also tool that are equipped with a cutting device. That cuts away the typical "collar" of the plastified material that has flowed upwards, so that an even top surface is the result.