Fig. 6. Cutter-head with Four Boring Tools
A disk-shaped head having four cutters is illustrated in [Fig. 6]. The cutters are inserted in slots or grooves in the face of the disk and they are held by slotted clamping posts. The shape of these posts is shown by the sectional view. The tool passes through an elongated slot and it is tightly clamped against the disk by tightening nut n. This head is also driven by a key which engages a keyway in the boring-bar.
Fig. 7. Cutter-heads equipped with Adjustable Tools
Two other designs of cutter-heads are shown in [Fig. 7]. The one illustrated at A has three equally spaced cutters which are held in an inclined position. The cutters are clamped by screws c and they can be adjusted within certain limits by screws s. The cutters are placed at an angle so that they will extend beyond the front of the head, thus permitting the latter to be moved up close to a shoulder. The cutter-heads shown in [Figs. 5] and [6] can also be moved up close to a shoulder if bent cutters are used as shown in the right-hand view, [Fig. 5]. The idea in bending the cutters is to bring the cutting edges in advance of the clamping posts so that they will reach a shoulder before the binding posts strike it. The arrangement of cutter-head B ([Fig. 7]) is clearly shown by the illustration.
Cutter-heads are often provided with two sets of cutters, one set being used for roughing and the other for finishing. It is a good plan to make these cutters so that the ends e ([Fig. 6]) will rest against the bar or bottom of the slot, when the cutting edge is set to the required radius. The cutters can then be easily set for boring duplicate work. One method of making cutters in sets is to clamp the annealed stock in the cutter-head and then turn the ends to the required radius by placing the head in the lathe. After both sets of cutters have been turned in this way, they are ground to shape and then hardened.
Fig. 8. Boring Tools for Roughing and Finishing Cuts