What is a milling tool?
The milling cutter has an important part of the milling machine. A milling tool is a rotating tool having one or more teeth for milling.
During operation, each cutter tooth intermittently cuts off the rest of the workpiece.
The milling cutter is mainly used for milling plane, step, groove, forming surface, cutting workpiece, etc.
Significance of milling tools
In a typical milling operation, the tool in the milling machine moves perpendicular to its own axis, so that it can remove excess material from the workpiece around the tool.
A milling machine is a widely used machine, which can perform a variety of machining operations. Milling machines are used to process and manufacture parts of various shapes and sizes. Milling cutter is a necessary tool to perform these tasks.
Types of milling tools
In order to make milling a general machining process, there are a variety of milling cutters available on the market.
These milling cutters are manufactured in various sizes, shapes and materials. Some milling cutters are made of high-speed steel (HSS), while others are carbide tips.
1. End mill:
There are cutting teeth on both sides of the end mill.
Therefore, this tool can be very successfully used in a variety of drilling operations.
The name “end mill” is a common term for flat bottomed tools. The main difference between drill bit and end mill is that the drill bit can only cut in the axial direction, while the end mill can cut in all directions.
End mills contain one or more chip removal slots and are ultimately used for various milling operations.
It is made of high speed steel or hardened material.
There are usually two variants of this tool.
One is commonly known as central cutting, which has cutting edges on both sides of the tool, and the other is non central cutting edge, in which the cutting edge is only on one side.
2. Rough milling cutter:
Rough end milling cutter is also commonly known as “Pippa” cutter.
These end mills provide excellent performance under the most severe operating conditions.
As the name suggests, they are used to extract a large amount of unwanted material from the workpiece. Generally, this kind of tool has more wavy teeth.
Rough end mills produce very small chips, resulting in a rough surface finish.
3. Peripheral milling cutter:
When the cutting teeth on the milling cutter exist on the circumference or periphery of the disc, these types of milling cutters are called circumferential milling cutters or peripheral milling cutters.
These milling cutters can only be used in horizontal milling machines.
4. Side milling cutter:
The side milling cutter is another type of milling cutter. Its cutting teeth exist not only in the periphery, but also in the face or end.
Side milling cutter is generally used for strand milling operation and face milling operation.
They can also be used to cut grooves and make deep and narrow grooves.
5. Face milling cutter:
The face milling cutter comprises a large diameter cutting body with a plurality of mechanically fixed plug-in blades.
Through the cutting stroke of the face milling cutter and through deep radial and narrow axial cutting, a lot of unnecessary materials can be removed.
The diameter of the face milling cutter body usually depends on the length of the workpiece and the available clearance on both sides of the workpiece.
These face milling cutters can also be used for forwarding milling operations. The face milling cutter is a very rigid cutting tool.
The surface finishes it provides depends on the feed rate and the number of teeth on the tool.
6. Concave milling cutter:
Concave milling cutter belongs to the category of forming cutter. The forming tool is usually designed to create a specific shape on the workpiece.
This milling cutter is a specially manufactured tool designed to correspond to the convex surface of a circular profile. The circular profile is usually equal to or less than a semicircle.
7. Woodruff tool:
“Woodruff” cutting tools are usually used to cut keyways in wood materials.
The edge of the wood grain cutting tool is slightly hollow, and its teeth are not used for side cutting. Its tooth profile has two types: straight teeth and staggered teeth.
8. Thread milling cutter:
Thread milling cutter is a cutting tool used to cut the external thread and internal thread tooth profile of the workpiece.
The cutting process using thread milling cutter can process single pitch thread or variable pitch thread from m2 to 1mm nominal diameter.
9. Ball end milling cutter:
Ball end mills are also commonly referred to as ball nose mills. These milling cutters are named for their hemispherical cutting ends.
This milling cutter is usually used to reduce stress concentration during operation. It is usually suitable for machining the three-dimensional surface shape of the workpiece.
10. Flying Cutter:
The flying cutter is composed of the main body in which one or two cutter heads are inserted.
As the cutter head rotates, the cutter head will cut narrower or wider.
Face milling cutters are more common in various cases, but they are expensive, and these flying cutters can also complete the processing content of face milling cutters.
The price is very cheap, but the cutting efficiency is far lower than that of face milling cutters.
Selection principle of milling cutter
1. Selection of milling cutter diameter
The selection of milling cutter diameter varies greatly due to different products and production batches.
The choice of tool diameter mainly depends on the specification of the equipment and the machining size of the workpiece.
Plane milling cutter
When selecting the diameter of face milling tool, it is mainly considered that the power required by the tool should be within the power range of machine tool, or it can be selected according to the diameter of machine tool spindle.
The diameter of face milling cutter can be selected according to D = 1.5d (d is the diameter of spindle).
In mass production, the tool diameter can also be selected according to 1.6 times of the cutting width of the workpiece.
The selection of end milling cutter diameter shall mainly consider the requirements of workpiece processing size to ensure that the power required by the cutter is within the rated power range of the machine tool.
If it is a small diameter end mill, the main consideration should be whether the maximum number of revolutions of the machine tool can reach the minimum cutting speed of the tool (60m / min).
The diameter and width of the slot milling cutter shall be selected according to the size of the workpiece to be machined, and its cutting power shall be within the allowable power range of the machine tool.
2. Selection of milling cutter blade
a. For finishing. It is best to use a grinding blade. This kind of blade has good dimensional accuracy, so milling is the positioning accuracy of cutting edge, which can obtain better machining accuracy and surface roughness.
b. For rough machining, it is best to use pressing blades, which can reduce the processing cost.
The dimensional accuracy and sharpness of the pressing blade are worse than those of the grinding blade, but the edge strength of the pressing blade is better. It is impact resistant during rough machining, and can withstand large cutting depth and large feed.
c. Sharp large rake blades can be used for milling viscous materials such as stainless steel. Through the cutting action of the sharp blade, the friction between the blade and the workpiece material is reduced, and the chips can leave the front end of the blade faster.
3. Selection of milling cutter blade
(a). First of all, the number of teeth must be considered when selecting milling cutter.
The size of tooth pitch will determine the number of cutter teeth involved in cutting at the same time, and affect the smoothness of cutting and the requirements for the cutting speed of the machine tool.
Rough tooth milling cutter is mostly used for rough machining because it has a large chip removal groove.
At the same feed rate, the cutting load per tooth of the coarse tooth milling cutter is greater than that of the dense tooth milling cutter.
(b). During finish milling, the cutting depth is shallow, generally 0.25-0.64mm. It is recommended to select dense tooth milling cutter.
(c). In the process of heavy rough milling, the excessive cutting force will lead to the chatter of machine tools with low rigidity.
This chatter will lead to the edge collapse of cemented carbide blade, which will shorten the tool life.
Using coarse tooth milling cutter can reduce the requirement of machine tool power.
Therefore. When the size of the spindle hole is small (such as R8, 30#, 40# taper hole), rough tooth milling cutter can be used for effective milling.
Whether we choose milling cutter on CNC milling machine or ordinary milling machine, we should comprehensively consider the milling material and hardness and the specifications of milling cutter, such as edge length, tool length, edge diameter, shank diameter, etc.
High speed steel milling cutters are usually suitable for ordinary milling machines, while cemented carbide cutters are preferred for CNC milling machines.