Shell milling is large milling cutters that are typically used for side milling and face milling. It is also called a shell mill or shell milling cutters. Shell milling removes the metal materials by the movement within the milling machines. The construction of shell milling cutters takes modular forms. In other words, the shanks or arbors of the shell milling cutters are separated from the cutter body which have multiple flutes and teeth. Take the face shell mill for example, the shanks or arbors can attach to the cutters via the rectangular cutout area.
The shell body and the shank or arbor are attached through several standard joining manners. Shell endmill cutters feature face cutting edge and peripheral cutting edge, which enable the cutters to perform both side milling and face milling. The hole of the shell endmill cutters allows the bolt to locate and secure it to the spindle. The Side-and-face shell milling has teeth around the face as well as one side of the cutting tool. The design makes the shell milling’s function similar to end mill cutters, but this type is less popular today. As for the side shell milling cutters, they have cutting edge on the sides and also on the periphery, allowing the cutting tools to mill slots.
High speed steel and tungsten carbide are the most general cutter material. Most shell milling cutters are made of high-speed steel, which refers to cobalt steel, alloy steels. It is cost-efficient but however has the shortest life. To prolong the shell milling cutter’s life and also fasten the cutting process, it is recommended to choose materials like cobalt-bearing high-speed steel, which can work approximately 10% over regular materials.
As above-mentioned, the construction of shell mill takes the modular form, and the shanks or arbors are separated from the cutter bodies. Following are the reasons that modular style of construction is suitable for this large shell milling cutters. For manufacturers of shell milling, it is cost-efficient and more practical to make individual, separate parts than machining the whole cutting tools to adjust the feature and enhance the designs. All the design will be in relation to each other in that case.
The operators of milling machines can change some parts while keeping other settings the same. One shank or arbor for shell milling that costs 3000 NT dollars can reuse and serve for a variety of shell milling at different times. The modular style of construction can effectively save the cost by only changing different shells or crushed shells rather than the whole set. To avoid the damage and even greatly save the cost, the operator can also use replaceable shims. The part can be mounted to the shell milling cutters, the inserts can be installed on the shims. The replacement of insert and shim can prolong the cutting tools’ life.
● Flutes: The flutes refer to the helix grooves on shell milling cutters and other cutting tools. Within the milling machine, the shell milling removes the metal materials, and the metal chips will be pulled out by the spiraled flutes with the rotation.
● Helix angle: In milling cutters, low helix angle designs are more suitable for heavy and difficult metals, and higher helix angles are ideal for soft materials with stringy chips. As a result, the large shell milling often has low helix angle designs. The flutes and teeth construction should always be spiraled, otherwise, the straight flute cutters can only mill and cut the pieces at once, resulting in poor surface, low precision, and inefficient material removal. If the operators of milling machines intend to remove the material rapidly by using the large shell milling, it is important to check the helix angle and the features of metal materials.
● Teeth: Along the flutes, there are sharp blades which are responsible for cutting and milling the materials, which are known as the teeth. Typically, one flute has one tooth along with it, however multiple teeth design allows faster cutting and rough milling for a high volume of metal materials. The type and amounts of the teeth are vital to affect the finishes and smoothness of the products. For example, jagged teeth leave rough finishes.
● Shank: Shanks are the non-fluted part which is separated from the shell milling. They are used to locate the shell mill in the holder of milling machines. The diameter varies, and it is often different from the shell in order to meet the size of the holder.
● Coatings: Coating of the shell mill can significantly enhance the cutter’s life and cutting speed, and also reduce the wear in the milling process.
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