What Is a Fly Cutter?
A fly cutter, also called a front face fly cutter or face mill, is a tool that is primarily attached to a milling machine and rotates a cutting tool to cut the workpiece on the table.
Compared to other cutting tools, fly cutters have a wider cutting area at a time, so they can efficiently machine a wide flat surface or side surface by cutting it all at once. Since cutting a flat surface is often the first step in various workpieces, fly cutters are almost indispensable cutting tools for metalworking.
Uses of Fly Cutters
Fly cutters are used for machining surfaces such as flat surfaces, sides, and stepped surfaces due to the large area that can be machined at a time, and they can also be used for machining with high surface accuracy.
Generally, due to the large diameter of the blade, multiple inserts are evenly distributed around the circumference of the blade.
Since the number of inserts, outer diameter, and even the angle of blade attachment differs depending on the type of fly cutter, it is often necessary to use multiple fly cutters together, even when machining flat surfaces.
Principle of Fly Cutters
The larger the diameter of the cutter, the more area it can cut. At the same time, the greater the load on the machine, so a machine tool with more power is required.
The larger the number of inserts, the smaller the load applied to each insert and the greater the cutting volume per revolution. Therefore, a cutter with a larger diameter and more inserts has higher machining efficiency. On the other hand, a large number of cutters with a large diameter and a greater number of blades will have high machining efficiency, but care must be taken when roughing out a substantial number of chips.
There are also two types of blade installation angles, one is the insertion angle when the cutter is viewed from the side (axial rake angle) and the other is the insertion angle when viewed from the back (radial rake angle), depending on the type and application. For example, for soft metals such as aluminum and copper, select a cutter with a large radial rake angle. For hard, crispy metals such as cast iron, select a cutter with a small radial rake angle to emphasize chip evacuation.
Side Cutter for Milling
Side cutters are used when milling large quantities of long, deep grooves, especially when using horizontal milling machines.
Side cutters can be used to perform groove milling operations such as open grooves, closed grooves, gang slitting, and butt cutting.
Side cutters are available in a variety of diameters and thicknesses, which can be used to achieve the desired groove length and depth.
When using side cutters, the cutter size, pitch, and position must be controlled so that at least one cutting edge always bites into the cutting area. It is also recommended that cutting with side cutters be performed by gown cutting.
Cutting Conditions for Fly Cutters
Cutting conditions for fly cutters include cutting speed, feed rate, and outer cutter diameter, which are set according to the cutter material used and the material to be cut.
The feed rate is set relatively low when priority is given to extending cutter life, when the workpiece is hard, when rough machining is performed, or when wear progresses rapidly.
On the other hand, if the material has good machinability, or if a smooth finished surface is required for finish cutting or precision finishing, the feed rate is set relatively high.
The feed rate per blade (calculated from the feed rate, number of cutter blades, and number of cutter revolutions) is set relatively high when the shape of the workpiece cannot be stably fixed, when the workpiece is too thin to be stably fixed, or when a smooth finished surface is required such as finish cutting or precision finishing. When a smooth finish surface is required, when the cutting edge causes chipping and the feed rate does not fall below the minimum feed rate even if the feed rate is lowered, or when deep grooves are to be cut, the feed rate is set relatively low.
On the other hand, when heavy cutting is performed on a rigidly mounted workpiece, when a material with good machinability is used, when the surface to be machined is intermittent, when wear on the flank surface increases rapidly, or when the machine is bivy, the feed rate is set relatively high.