Page:Practical Treatise on Milling and Milling Machines.djvu/103

Rh for it is rarely used outside of the tool room or in experimental shops, but there it fills an important place. As it has only one cutting edge, it mills accurately to its own shape, but it does not cut so fast or wear as long as cutters with a number of teeth. It can be formed very exactly to any desired shape at a comparatively small expense, and thus may be used for many operations that otherwise would not bear the cost of special cutters, as, for example, when one or two teeth of special form are wanted in experimental work. The outlines of several possible shapes are shown in connection with the figure.

Fig. 54

Right and Left-Hand Cutters. Cutters or end mills with taper shanks and those which have end teeth, may be either right or left- hand, according to the direction in which the cutting edges of the teeth point. Taking an end mill for example, a right-hand mill is one which, held in the hand with the teeth away from you, presents the cutting edges of the teeth when revolved to the right or clock-wise. A left- hand mill is one that, similarly held, presents the cutting edges of its teeth when revolved to the left. Milling cutters having straight holes can be used either right or left-hand as desired. Inserted Teeth. Plain milling cutters above 8 inches diameter, side milling cutters above 6 inches diameter, and face milling cutters, are usually made with inserted teeth. The body of the cutter is of steel, the teeth being held securely in place by various means. We employ a bushing and screw for this purpose, as shown in Fig. 54.

The introduction of cutters of this style has done more for heavy milling than any other improvement in the cutter line, for with them the heaviest and fastest cuts can be taken, and shouldany of the teeth become broken, it is not a question of a new cutter, but simply that