When selecting a milling cutter suitable for the machining task, various problems of the geometry, size and workpiece material of the workpiece to be machined must be considered.
Milling cutter lead angleThe lead angle is the angle between the cutting edge and the cutting plane. The lead angle has a great influence on the radial cutting force and depth of cut. The amount of radial cutting force directly affects the cutting power and the anti-vibration performance of the tool.
The smaller the main deflection angle of the milling cutter, the smaller the radial cutting force and the better the vibration resistance, but the cutting depth is also reduced.
Use a 90° lead angle when milling the plane with the square shoulder. This type of tool has good versatility and is used in single and small batch processing. Since the radial cutting force of the tool is equal to the cutting force, the feed resistance is large and the vibration is easy, so the machine tool is required to have large power and sufficient rigidity.
When machining the plane with the shoulders, a cutter with an 88° lead angle can also be used. Compared with the 90° lead angle milling cutter, the cutting performance is improved. Planar milling of 90° square shoulder milling cutters is also very common. In some cases, this choice is justified. The irregular shape of the workpiece being milled or the surface of the casting will cause a change in the amount of depth of cut, square shoulder milling cutters may be the best choice. In other cases, however, a standard 45° face milling cutter may benefit more.
When the plunging angle of the milling cutter is less than 90°, since the chip thickness is thinner and the axial chip thickness is smaller than the feed rate of the milling cutter, the cutter plunging angle will have a great influence on the feed amount per tooth to which it is applied.
In face milling, a face milling cutter with a 45° cut-in angle will make the chips thinner. As the plunging angle decreases, the chip thickness will be less than the feed per tooth, which in turn will increase the feed rate by a factor of 1.4.
The radial cutting force of the 45° lead angle milling cutter is greatly reduced, which is approximately equal to the axial cutting force. The cutting load is distributed on the longer cutting edge and has good vibration resistance. It is suitable for overhanging of the boring and milling machine spindle. Longer processing occasions. When the plane is machined with this type of tool, the blade has a low breakage rate and high durability; when machining a cast iron piece, the edge of the workpiece is less likely to cause chipping.
Milling cutter size selectionThe standard indexable face milling cutter has a diameter of Φ16——Φ630mm. The diameter of the milling cutter should be selected according to the milling width and depth. Generally, the larger the depth and width before milling, the larger the diameter of the milling cutter should be. When roughing, the diameter of the milling cutter is smaller; when milling, the diameter of the milling cutter is larger, try to accommodate the entire processing width of the workpiece, and reduce the marking between the two adjacent feeds.
In the face milling of large parts, the smaller diameter milling cutters are used, which leaves a lot of room for productivity. Ideally, the cutter should have 70% of the cutting edge involved in the cutting. Tool size becomes especially important when milling a hole with a milling cutter. The diameter of the milling cutter is too small relative to the bore diameter, and a core may be formed in the center of the hole during machining. When the core is dropped, the workpiece or tool may be damaged. If the cutter is too large, it will damage the tool itself and the workpiece. Because the cutter is not cut in the center, it may collide at the bottom of the tool.