Flow Drilling – Flow Tapping

Flow drilling is a non-cutting method for drilling holes into metal, in which the material is melted by adding high pressure and frictional energy.

Flow Tapping is also a non-cutting method. The screw-thread is rolled.

Operating principle:

Flow Drilling makes use of a highly heat-resistant hard metal pointed object. This is pressed against a workpiece at high speed. As a result, locally developed a lot of frictional heat, whereby the material of the workpiece reaches a temperature where the metal becomes liquid. The flow drill collapses, as it were, through the workpiece, with the formation of a hole. The liquid material does not get lost, but forms a bushing, The bushing has a length of the original wall thickness about three times.

Advantages:

• Very fast process.
• Due to formation of the bushing around the flow drilled hole, it is possible to attach objects (f.e. bolts) with a high strength in very thin plate material.
• It is a clean process, because there is no waste (chips) produced.
• Higher quality of the threaded connection.
• In comparison to cut thread, for thread forming no use is made of cut-machining. This offers advantages in respect to cut thread, which is produced during the normal tapping. The tension lines where many force is applied to, are in a rolled thread half round. This gives rise to a tension line that is not interrupted. In the cut thread is the tension line interrupted, which makes it less strong. There is little difference in capacity at a static load, but under dynamic load, there is an increased risk of fatigue failure to cut thread. A rolled thread, by dynamic loading, therefore, is to be preferred.

Disadvantages:

The process cannot be used in full or solid material. The fluid material has to go somewhere. However, it is possible to apply the flowdrill process to material up to twelve (12) mm thickness.

A = Starting position

B = By pressure and rotation, frictional heat is generated, that makes the material fluid. Finally the tool is being pushed through the material.

C = Thread rolling

Field of application:

• Flow Drilling is applied to thin-walled material such as plate, tube and box-shaped profile.
• Not all material is suitable for the application of this technique. but it can be applied to steel with a tensile strength <700N / mm², no brittle material, aluminium, stainless steel, copper and brass.

Examples:

• In a relatively thin-walled pipes, hollow sections or sheet metal, normally, no threaded holes can be tapped . By including the bushing, which occurs during the flow drilling, a rolled screw thread, can be made, containing the possibility for a high-strength bolted connection. (For example: for the inclusion of a bottle- and/or a luggage rack in a bicycle frame.)
• By means of flow drilling, in one movement, a hole in plate material, can be obtained, in which a bearing can be pressed.
• In a bushing formed by means of the flow drilling, a tube may be pressed. (For example: a heat exchanger).