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Improved Economy with Octagonal Inserts for Semi-Finishing and Finishing
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New octagonal inserts shown in Figure 3 offer eight cutting edges, each with 45° lead angles, for more economical milling applications.
Inserts combining helical cutting edges [A], a large axial angle, and a rib-type rake face design [B] offer a self-balanced, stable tool for cost reduction and high performance in semi-finishing and finishing. The sloped, untaught cutting-edge inserts make it possible to use fine-pitch cutters with more inserts on the same body. This enables machining with higher loads and higher feed
The special protruding wiper flat design on each of the eight cutting edges [C] offers, at the same time, good surface finish. Inserts are normally available in the economic M-pressed-and-sintered versions with ground wipers for even higher surface quality. The arrows ]D] on the rake face indicate the indexing direction to insure maximal usage of all eight cutting edges at small cutting depths [up to 2.45mm]. At larger depths the number of effective edges is less than eight. Therefore, the highest economical advantage is expected in the finishing range.
The insert is equipped with a sequence of depressions to reduce the contact area between the chip and insert rake face to reduce heat penetration into the insert, to reduce friction, and to improve tool life. The positive rake angle in combination with these depressions also reduces cutting forces and machining power. The positive rake face of these octagonal inserts meets the demand to machine smaller workpiece oversizes with less stock removal on low-powered machines.
Figure 3 shows also a variety of possible machining options. Both octagonal and round inserts may be mounted on the same cutter bodies. Operation A is facing at low forces and a small depth of cut, providing a good surface quality. Operation B is a deep plunging operation in which the frontal, side and 45° cutting edges are all active at the same time. Operation C shows plunging and facing and Operation D demonstrates machining of a slot with a round or shaped profile. Operation E is a few, successive 45° slotting steps, and operation G is a side shouldering application. The final operation, F, is a chamfering operation making use of the 45° cutting-edge configuration.
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