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Technology Knurling


Knurling tools and knurling wheels

During the seventies the company specialised in the production of knurling tools. The lateral knurling tools every popular at that time did not comply with the quality requirements of Böni AG and knurling results failed to convince also.

Further developments of knurling tools involved the tangential functioning of knurling tools. The knurling wheels have been arranged in the centre of the workpiece,180 degrees opposite. Consequently, there is almost no lateral pressure. So this enables knurling thin and long parts reliably. The overall work pressure during knurling is accepted by the tangentially arranged sliders. No harmful lateral pressure is exerted on the workpiece, the turning spindle and the ball screw of the lathe.

Nowadays, it is the utmost priority that expensive capital goods such as lathes are used carefully and best possible. So the objective is to achieve the best result by an ideal interaction of machine and tool. The further development of knurling tools in tangential construction exactly meets the requirements to modern and reliable precision tools and consequently achieves the very best cost-benefit factor.

There are two systems available on the market. On the one hand it is the lateral functioning in which one or two knurling wheels are laterally pressed into the workpiece, or the tangential functioning in which two or three knurling wheels are pressed into the material.

Disadvantages of lateral functioning of knurl pressing and knurl milling tools:
The functioning of lateral knurl pressing or knurl milling tools is anything but machine- and workpiece-sparing and has some distinctive disadvantages:

  • Increased handling costs due to complicated and unreliable settings.
  • Large, lateral and longlasting working pressure strains the machine and ball screw as well as the workpiece. Repair work of worn spindle ball bearings or spindles rapidly amounts to some 10,000 Euros.
  • Due to the lateral pressure on the workpiece the workpiece may move which may result in an inferior, uneven knurl.
  • Due to the bouncing of the workpiece during pressing laterally the knurl does not become cylindrical.

    All these disadvantages can be avoided by selecting a tangential knurling tool. However, tangential functioning requires distinguishing between tools with 2 and 3 knurling wheels. Tangential tools with 3 knurling wheels allow to produce a knurl in the z-axis direction only. After knurling application, the tool is required to go back in the same position an so practically needs twice the working time. Or the tool utizlizes special equipment with the knurling wheels standing free after knurling in order to allow the tool running back quickly. For this purpose, the lathe requires a special fixture or connection for moving the knurling wheels of the tool in start position again.

    With 2 knurling wheels and a tangential tool knurling is possible in the z-axis as well x-axis direction. Double knurling time is not applicable.

    The modular standard knurling system of Böni AG always allows to compile the ideal tool combination. In doing so, by selecting the suitable knurling wheels it is possible to form (cold-rolled) or cut (milled) a knurl. In case of special requirements our technician will be available for customized tool solutions up to your demand.


Knurling is a kind of processing involving great forces, whether rolling or cutting. These high forces cause a large lateral pressure acting on the workpiece and the machine. Since machine tools are expensive investment commodities, we would like to make processing as machine-saving as possible. We therefore almost exclusively rely on knurling in tangential procedure. In this process, two knurling wheels process the workpiece by 180 degrees tangially to the turning centre, refer to picture 1.typo3conf/ext/boeniag/Raendeln/Skizze_tangential_01.png.

Due to this arrangement of the knurling wheels no lateral pressure is exerted on the workpiece and the machine. The forces arising are accepted by the knurling tool. A further enormous advantage of this processing is provided by knurling thin or long components. Due to the tangential processing the workpiece is always located between the knurling wheels without being pressed away. So a deviation in diameter during knurling will be avoided. For comparison: knurling laterally with one knurling wheel, refer to picture 2.

Picture 1:
Tangential mode of operation.
Two knurling wheels 180 degrees tangentially to the turning centre.

Picture 2:

Lateral mode of operation.
Owing to the pressure exerted by the knurling wheel on the workpiece
the workpiece bends away.


There are two knurling procedures for attaching a knurl at the workpiece. By knurl forming also called knurl rolling and knurl cutting, also called knurl milling.


Knurl forming is the non-cutting processing and applicable for all cold forming materials. Due to the pressure exerted by the knurling wheel on the workpiece material, the material flows to the knurling wheel and forms the tip in the material. Milled knurls often feature an increased strength and decreased elongation at break. Forming makes the external diameter of the workpiece larger than the pre-machined diameter.


Knurl cutting is a chip removing process and is applied for all materials that are difficult to form such as plastics, brass without lead alloy, cast, heat-treated aluminium and chrome steel containing more than 16% chrome. The knurling wheels must be positioned obliquely to the axis of rotation for enabling the knurling wheel to execute cutting processing.

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