Selection of carbide milling cutter materials
Except for end mills and some face mills, which use carbide as the tool material, other types of milling cutters mostly use high-speed steel, especially tungsten-molybdenum series and high-vanadium high-speed steel, which have good performance. The tool durability can be improved by 1 to 2 times compared with W18Cr4V. The Chinese carbide grades suitable for making milling cutters include YG8, YW2, YS2T, YS30, YS25, etc. Friends who are not familiar with Chinese grades can check the corresponding table between Chinese carbide grades and international grades.
Classification of milling cutters.
Cylindrical milling cutters
They are used for machining surfaces on horizontal milling machines. The teeth are distributed on the circumference of tool and are divided into straight teeth and spiral teeth according to their shapes. According to the number of teeth, they are divided into coarse teeth and fine teeth. Spiral coarse-tooth milling cutters have fewer teeth, high tooth strength, and large chip space, and are suitable for rough machining. Fine-tooth milling cutters are suitable for precision machining.
Face milling cutter
It’s used for machining surfaces, end faces, and circumferences on vertical milling machines, end milling machines, or gantry milling machines. There are teeth on both the end face and circumference, and they can be divided into coarse teeth and fine teeth. Its structure includes three types: integral type, insert type, and indexable type.
It’s used for machining grooves and stepped surfaces, etc. The teeth are on both the circumference and end face, and the tool cannot be fed axially during operation. When there is an end tooth passing through the center of the vertical type cutter, axial feeding is possible.
Three-edge milling cutter
It’s used for machining various grooves and stepped surfaces, with teeth on both sides and circumference.
Chamfer milling cutter
It’s used for milling grooves at a certain angle, with two types of single-angle and double-angle milling cutters.
Saw blade milling cutter
It’s used for machining deep grooves and cutting workpieces, with more teeth on the circumference. In order to reduce friction during milling, there is a secondary relief angle of 15’~1° on both sides of the teeth. In addition, there are keyway type cutters, dovetail slot cutters, T-slot cutters, and various shaping milling cutters.
Main milling methods
There are two main types of milling methods for milling cutters in relation to the feed direction of the workpiece and the rotation direction of milling cutter:
The first is climb milling, in which the rotation direction of the milling cutter and the feed direction of the cutting are the same. When cutting starts, this type of tools bite into the workpiece and cuts the final chips.
The second is conventional milling, in which the rotation direction of the cutter and the feed direction of the cutting are opposite. The tool must slide on the workpiece before cutting starts, with the cutting thickness starting at zero and gradually increasing until the end of cutting.
During climb milling, the cutting force presses the workpiece against the worktable, while during conventional milling, the cutting force lifts the workpiece off the worktable. Since climb milling produces the best cutting effect, it is usually preferred. Only when there is a problem with backlash in the machine tool or when climb milling cannot solve the problem should conventional milling be considered.
For example, when milling stainless steel, climb milling should be used as much as possible. Asymmetric climb milling ensures that the cutting edge smoothly cuts away from the metal, reducing the contact area of the chips. Therefore, climb milling can reduce the occurrence of chipping and edge wear on the front cutting edge, improving the durability of the milling cutter.
Maintenance of Milling Cutters
When the axis of the milling cutter coincides with or approaches the edge of the workpiece, the situation will be very serious, and the operator should do relevant equipment maintenance work:
1Check the power and stiffness of the machine tool to ensure that the required cutter diameter can be used on the machine tool.
The overhang of the tool on the spindle should be as short as possible to reduce the impact of the position of the cutter axis and the workpiece on the shock load.
2Use the correct cutter tooth pitch suitable for the process to ensure that there are not too many blades engaged with the workpiece at the same time during cutting, and ensure that there are enough blades engaged with the workpiece when milling narrow workpieces or milling cavities.
3Ensure that the feed rate of each blade is adopted so that the correct cutting effect can be obtained when the chip thickness is sufficient, thereby reducing tool wear. Use a positive front angle groove-shaped indexable insert to obtain smooth cutting effects and the lowest power.
4Choose cutter diameter suitable for the width of the workpiece.
5Choose the correct main angle.
6Place the cutter correctly.
7Use cutting fluid only when necessary.
8Follow the rules of tool maintenance and repair, and monitor tool wear.