Milling of flat surfaces

Peripheral Milling

In peripheral milling, also called plain milling, the axis of the cutter is parallel to the surface being machined, and the operation is performed by cutting edges on the outside periphery of the cutter. The primary motion is the rotation of the cutter. The feed is imparted to the workpiece.Several types of peripheral milling are shown in the figure:

v slab milling, the basic form of peripheral milling in which the cutter width extends beyond the workpiece on both sides;

v slotting, also called slot milling, in which the width of the cutter, usually called slotter, is less than the workpiece width, creating a slot in the workpiece. The slotter has teeth on the periphery and over the both end faces. When only the one-side face teeth are engaged, the operations is known as the side milling, in which the cutter machines the side of the workpiece;

v straddle milling, which is the same as side milling, only cutting takes place on both sides of the work. In straddle milling, two slotters mounted on an arbor work together;

v when the slotter is very thin, the operation called slitting can be used to mill narrow slots (slits) or to cut a workpart in two. The slitting cutter (slitter) is narrower than the slotter and has teeth only on the periphery.

Some of the advantages of peripheral milling include,

· More stable holding of the cutter. There is less variation in the arbor torque;

· Lower power requirements;

· Better work surface finish.

Face milling

In face milling, cutter is perpendicular to the machined surface. The cutter axis is vertical, but in the newer CNC machines it often is horizontal. In face milling, machining is performed by teeth on both the end and periphery of the face-milling cutter. Again up and down types of milling are available, depending on directions of the cutter rotation and feed.

Face milling is usually applied for rough machining of large surfaces. Surface finish is worse than in peripheral milling, and feed marks are inevitable. One advantage of the face milling is the high production rate because the cutter diameter is large and as a result the material removal rate is high. Face milling with large diameter cutters requires significant machine power.

End milling

In end milling, the cutter, called end mill, has a diameter less than the workpiece width. The end mill has helical cutting edges carried over onto the cylindrical cutter surface. End mills with flat ends (so called squire-end mills) are used to produce pockets, closed or end key slots, etc.: