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 frame

Bicycle frame

A bicycle frame is the main component of a bicycle, on to which wheels and other components are fitted. The modern and most common frame design for an upright bicycle is based on the safety bicycle, and consists of two triangles, a main triangle and a paired rear triangle...

s, heat exchanger

Heat exchanger

A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...

s, and to create holes for mounting bearings

Bearing (mechanical)

A bearing is a device to allow constrained relative motion between two or more parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation as well as by the directions of applied loads they can...

.

History

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.

Principle

Friction drilling uses a very heat resistant cemented carbide

Cemented carbide

Cemented carbide, also called tungsten carbide, hardmetal, or widia, is a hard material used in machining tough materials such as carbon steel or stainless steel, as well as in situations where other tools would wear away, such as high-quantity production runs. Most of the time, carbide will leave...

, pointed but not sharp object. This device is pressed against a target material with both high rotational speed

Rotational speed

Rotational speed tells how many complete rotations there are per time unit. It is therefore a cyclic frequency, measured in hertz in the SI System...

 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

Drilling

Drilling is a cutting process that uses a drill bit to cut or enlarge a hole in solid materials. The drill bit is a multipoint, end cutting tool...

, 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.

Advantages

• Very quick process
• The process reshapes all material so that no material is lost. The sleeve that is about 3 times longer than the original diametre of the target material makes it possible to make very strong bolt joints in thin material.
• Moreover, it is a clean process, because no litter (particles) is produced.

Disadvantages

• The friction drilling process is not possible in massive material: The melting metal must be able to flow somewhere. Yet it is possible to friction drilling holes in subjects up to 12 mm thick.
• The target material must be able to withstand the added heat. Materials that have been painted, plastic coated, or materials that have been galvanized
  Galvanization
  Galvanization is the process of applying a protective zinc coating to steel or iron, in order to prevent rusting. The term is derived from the name of Italian scientist Luigi Galvani....
  
  , are often unsuitable for this process.