Correct selection of grooving cutter

Mon Jul 04 14:42:15 CST 2022

Grooving can be one of the most difficult parts of turning processes, and the geometry of these processes can be very complex. In typical slotting processes, cutting with the main cutting edge (sometimes full, sometimes partial) and with one or both sides of the side cutting edge may require both radial and axial cutting forces.

Depending on grooving requirements, the operator may use a insert that is sintered at the end before the cutter surface shape (groove width is usually the determining factor). However, for grooves with too narrow width, it is impossible to sinter the front face shape of the insert tip. In general, full-width grooves are the best solution to chip control problems. But how do you determine the correct insert geometry?

1. Slot width

Is the slot width to be machined the same as the standard slot blade width provided by the grooving cutting tool manufacturer?

If the slot width is the same, the cutting force is usually applied only to the main cutting edge. In this case, for better wall finish, a slot cutter that reduces chip width (forming chips away from the sides of the slot wall) is required.

If the width of the groove is different, you can choose to cut the full cutter first and then partially, or apply axial cutting force on the blade in turning mode. Regardless of the grooving method, it becomes more difficult to select the insert geometry that provides the best groove wall finish and chip breakage.

When selecting tool geometry, it is important to select the positive cutting geometry and understand the machining method to be used.

If the slot width is the same as the blade width, the selection of the cutter is much easier. At this point, the cutting tool feed strength must be determined according to the tensile strength of the workpiece material to be cut. If you look at the chipping table of the two blades, you will find that the distance from the front of the chipping table to the back edge is not the same.

When the distance is longer, the cutting will be smoother, but larger strip chip will be formed. If the tensile strength of the workpiece material is very low, this strip-shaped chip may be difficult to control and the chip may become entangled. Conversely, the shorter the distance, will form a more tightly rolled hair strip chip. However, if the tensile strength of the workpiece material is high, the impact of the chip may damage the main cutting edge.

If the slot to be machined is wider than the insert width, you can use multiple cutting to widen the groove, or you can use first cutting and then turning to process the wide groove.

If you choose multiple insertion and cutting processing, the simplest way is to carry out the first insertion and cutting, and then take the step of 50%-75% blade width again knife insertion and cutting; Repeat until the desired groove width is machined. This is the easiest way to program. However, cutting with only 50 to 75 percent of the slot width may make chip control difficult. If full-groove cutting is used, the chip is broken off from both sides of itself. When cutting with a partial slot width, chips can only break in one direction, which can lead to pigtail chips or other difficult to control chips.

A simple solution is to cut as much of the full slot width as possible and then use the center of the insert to remove the remaining workpiece material. In this way, you can take full advantage of all the advantages of a simple chip rolling table.

For cut-and-turn machining, it is best to use a roll table that can reduce chips from the front and leave a chip control area on the side of the blade. This requires more complex processing procedures, because when the cutting tool is near the bottom of the groove, workpiece material should not be removed from the front and side of the insert at the same time, as this often damages the insert and handle.

2. Workpiece material

What type of workpiece material does the slot need to be cut? The following categories, while not always entirely accurate, provide a good rule of thumb.

(1) short chip workpiece material

In general, chip control for such materials is very easy and the role of chip breaker is not very important. However, the cutting edge is required to be strong and durable. The workpiece materials with the shortest chip are cast iron, hardened steel and brass. In general, when processing these materials, the slot width is not important because the chip is easy to control.

(2) long chip workpiece material

Most workpiece materials fall into this category. Long chip workpiece materials can also be subdivided into different subclasses. Long chip workpiece materials include most carbon steel, alloy steel, stainless steel and high temperature alloy.

(3) "hard to break" workpiece material

These materials are usually forgings, carbon and alloy steels with very low tensile strength, and some tubes. Processing of such materials requires very strong chutes and, in some cases, a "pecking" cycle, but the cutback must not exceed the rate of feed per turn, otherwise chips may become trapped between the cutting edge and the workpiece material.

In addition, inner diameter grooving, face grooving and forming grooving also follow these basic principles, but each processing has its own characteristics.