What is a milling tool?
Milling cutters are an important part of milling machines. A milling tool is a rotating tool with one or more teeth for milling. During operation, each tooth intermittently cuts off the rest of the workpiece. Milling cutters are mainly used for milling planes, steps, grooves, forming surfaces, cutting workpieces, etc.
The meaning of milling tools
During a typical milling operation, the tool in the milling machine moves perpendicular to its own axis, allowing it to remove excess material from the workpiece around the tool. A milling machine is a versatile machine on which a variety of machining operations can be performed. Milling machines are used to machine and manufacture parts of various shapes and sizes. Milling cutters are essential tools for these tasks.
Types of milling tools
To make milling a versatile machining process, there are a wide variety of milling cutters available on the market. These milling cutters are manufactured in a variety of sizes, shapes and materials. Some milling cutters are made of high-speed steel (HSS), while others have carbide tips.
1. End mill:
End mills have cutting teeth on both sides; therefore, this tool can be used very successfully in a variety of drilling operations. The name "end mill" is a common term for flat bottom cutters. The main difference between drills and end mills is that drills can only cut in the axial direction, while end mills can cut in all directions. End mills contain one or more flutes that are ultimately used in various milling operations. It is made of high speed steel or hardened material. There are usually two variants of this knife. One of these is commonly known as center cutting, which has cutting edges on both sides of the tool, and the other is non-center cutting, where the cutting edges are on one side only.
2. Rough milling cutter:
Roughing end mills are also commonly known as "Pippa" cutters. These end mills provide outstanding performance under the toughest operating conditions. As the name suggests, they are used to extract large quantities of unwanted material from workpieces. Typically, use this type of cutter with more wavy teeth. Roughing end mills produce very small chips resulting in a rough surface finish.
3. Peripheral milling cutter:
When the cutting teeth on a milling cutter are present on the circumference or periphery of the disc, then these types of milling cutters are known as peripheral milling cutters or peripheral milling cutters. These milling cutters can only be used in horizontal milling machines.
4. Side milling cutter:
Side milling cutters are another type of milling cutter with cutting teeth present both on the perimeter and on the face or end. Side milling cutters are generally used in strand milling operations and face milling operations. They can also be used to cut grooves and make deep and narrow grooves.
5. Face milling cutter:
Face mills consist of a large diameter cutting body with mechanically secured insert inserts. With the cutting stroke of the face mill, a very large amount of unwanted material can be removed by making radially deep and axially narrow cuts. The diameter of a face mill cutter body is usually determined by the length of the workpiece and the clearance available on either side of the workpiece.
These face mills can also be used for climb milling operations. A face mill is a very rigid cutting tool and the surface finish it provides depends on the feed rate and the number of teeth on the tool.
6. Concave milling cutter:
Concave milling cutters belong to the category of forming tools. Forming tools are usually designed to create a specific shape on the workpiece. This milling cutter is a specially manufactured tool designed to correspond to the convexity of a circular profile. This circular profile is usually equal to or smaller than a semicircle.
7. Woodruff knives:
"Woodruff" cutting tools are commonly used to cut keyways in wood materials. Wood grain cutting knives have slightly hollow edges and their teeth are not used for side cutting. Its tooth shape has two types: straight tooth and staggered tooth.
8. Thread milling cutter:
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The thread milling cutter is a cutting tool used to cut the external thread and internal thread profile of the workpiece. The cutting process with a thread milling cutter can produce single-pitch or variable-pitch threads from M2 to a nominal diameter of 1 mm.
9. Ball end milling cutter:
Ball nose cutters are also commonly referred to as ball nose cutters. These milling cutters get their name from the hemispherical shape of their cutting ends. Such milling cutters are often used to reduce stress concentrations during operation. It is usually suitable for machining the three-dimensional surface shape of the workpiece.
10. Throwing Knife:
Throwing knives consist of a body into which one or two bits are inserted. As the cutter head rotates, the cutter head makes narrower or wider cuts. Face mills are more versatile in various situations, but they are expensive, and these flying cutters can also do what face mills do, and they are cheap, but far less efficient than face mills.
The principle of milling cutter selection
1. Selection of milling cutter diameter
The choice of milling cutter diameter varies greatly by product and production batch. The choice of tool diameter mainly depends on the specifications of the equipment and the processing size of the workpiece.
Face milling cutter
When selecting the diameter of the face milling tool, the main consideration is that the power required by the tool should be within the power range of the machine tool, or it can be selected according to the diameter of the machine tool spindle.
The diameter of the face milling cutter can be selected according to D=1.5d (d is the diameter of the main shaft).
In mass production, the tool diameter can also be selected according to 1.6 times the cutting width of the workpiece.
end mill
The selection of the diameter of the end mill should mainly consider the processing size requirements of the workpiece to ensure that the power required by the tool 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).
slotting knife
The diameter and width of the slot milling cutter should be selected according to the size of the workpiece to be processed, and its cutting power should be within the power range allowed by the machine tool.
2. Selection of milling cutter inserts
a. For finishing. The best option is to use a ground blade. This kind of insert has better dimensional accuracy, so the positioning accuracy of the cutting edge is high when milling, and better machining accuracy and surface roughness can be obtained.
b. For rough machining, it is better to use pressed inserts, which can reduce the machining cost.
The dimensional accuracy and sharpness of the pressed blade are worse than that of the ground blade, but the edge strength of the pressed blade is better, it is impact-resistant during rough machining, and can withstand large depth of cut and large feed.
c. Sharp, high-rake inserts are available for milling sticky 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 of the blade faster.
3. Selection of milling cutter body
a. First, when selecting a milling cutter, the number of teeth must be considered.
The size of the tooth pitch will determine the number of teeth involved in cutting at the same time during milling, affecting the smoothness of cutting and the requirements for cutting speed of the machine tool.
Coarse-tooth milling cutters are mostly used for roughing because they have larger flutes.
At the same feed rate, the cutting load per tooth of a coarse-tooth milling cutter is greater than that of a fine-tooth milling cutter.
b. When finishing milling, the cutting depth is shallow, generally 0.25-0.64mm, and it is recommended to use a fine-tooth milling cutter.
c. During heavy rough milling, excessive cutting forces can cause chatter in less rigid machines.
This chatter can cause chipping of the carbide insert, reducing tool life. The use of coarse-tooth milling cutters can reduce the power requirements of the machine tool.
therefore. When the size of the spindle hole is small (such as R8, 30#, 40# taper hole), it can be effectively milled with a coarse-toothed milling cutter.
epilogue
Whether choosing a milling cutter on a CNC milling machine or an ordinary milling machine, we must comprehensively consider the milling material and hardness, and the specifications of the milling cutter, such as: blade length, blade length, blade diameter, shank diameter, etc. High-speed steel milling cutters are usually suitable for ordinary milling machines, while CNC milling machines prefer carbide cutters.
