What Kind of Milling Cutter Is Used for Milling Keyway?

For a key to function, the shaft and rotating machine element must have a keyway and a keyseat, which is a slot and pocket in which the key fits.


The function of the keyway is generally used for the circumferential fixation of rotating parts to transmit torque and torque. The keyway is widely used in mechanical parts, and it is also inseparable from various gear transmission mechanisms. In the processing of the keyway, what kind of cutter is used for milling the keyway?

What is keyway milling?

Keyway milling is the process of using a milling machine to produce keyways. Keyway milling cutter is a kind of CNC milling tool, mainly used for processing keyway and closed depression.

In order to overcome the influence of radial cutting force, the keyway milling cutter is designed with two symmetrical cutting edges. During milling, the cutting forces on the two cutting edges are rectangular into a force couple, and the radial forces cancel each other out. Both the cylinder and the end face of the keyway milling cutter have cutting edges, and the end face cutting edge passes through the tool center, so it can be milled in the axial direction of the tool. It has the function of plunge drilling and can directly process the closed depression.

End mills generally have more than 3 cutting edges, and the center of the end face generally has a center hole. Therefore, it cannot be milled along the axis of the tool, and cannot directly process closed depressions. It is mainly used for semi-closed or open processing. Keyway milling cutters actually belong to a special end mill.

How to choose a keyway milling cutter?

The keyway can be divided into three types:

  • Open type
  • Semi-open type
  • Closed type

In the process of milling the keyway, the choice of milling cutter is strictly required, which directly affects the accuracy and surface roughness of the keyway. Under normal circumstances, milling the keyway is done with a disk milling cutter; milling the closed keyway often uses an end mill and a keyway milling cutter. Choice of milling cutter type when milling different keyways:

Milling closed keyway

Use an end milling cutter to mill the closed slot, and the diameter of the selected tool should be equal to or smaller than the slot width. Due to the force applied during milling, the end milling cutter tends to yield when its rigidity is poor. Excessive force may cause the cutter to break. Use the layered milling method to mill to the specified size, and the tool will be raised outside the expansion milling slot, and the tool can’t be caught back and forth. Climbing milling should be avoided when expanding the slot to avoid gnawing and hurting the workpiece.

Milling a half-open keyway

Use a carbide end mill to enlarge and mill the half-opened keyway, and the through-slot can not be milled with vertical feed. The hole should be drilled first, and then milled with an end mill smaller than the slot width, and then milled to the required width with a milling cutter equal to the slot width or milling with a shift cutter. Prevent down milling during expansion milling, and tighten unused directions at any time.

Milling an open keyway

Three-sided milling cutters are generally used to process right-angle grooves and stepped parts, but sometimes they can also be used to process open keyways. The processing method is equivalent to that of right-angled grooves and stepped parts. The difference is that you should be careful not to scratch the workpiece when setting the knife on the side, so as not to damage the surface quality of the workpiece. The milling method should also pay attention to the use of up-cut milling, and at the same time add coolant, and the cooling should be sufficient and timely to prevent the tool from being damaged by heat.

Milling the keyway with a keyway milling cutter

The keyway milling cutter can process various types of the keyway. When choosing the tool, you must pay attention to the trial cutting to prevent the error produced by the tool in the manufacturing process from making the keyway milling larger. Pay attention to the difference between down milling and up milling when milling, and be careful not to produce a broach phenomenon during down milling. In order to prevent punching during cutting, markings can be drawn on the longitudinal and transverse tables of the machine tool.

Finally, there are many types of keyways. When processing, it is necessary to analyze what milling cutter and processing method to use for the types of keyways. Flexible use to improve the efficiency of processing and production.

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