Machinery's Handbook, 31st Edition
840 INDEXABLE INSERTS other ductile materials form a continuous chip that must be broken into small segments when machined on lathes and planers having single-point, cemented carbide and cemented-oxide cutting tools; otherwise, the chips can cause injury to the operator. In this case a chipbreaker must be used. Some inserts are made with chipbreaker grooves molded or ground directly on the insert. When inserts with plain faces are used, a cemented- carbide plate-type chipbreaker is clamped on top of the insert. Identification System for Indexable Inserts.— The size of indexable inserts is deter mined by the diameter of an inscribed circle (I.C.), except for rectangular and parallelo gram inserts where the length and width are used. To describe an insert in its entirety, a standard ANSI B212.4-2002 identification system is used where each position number designates a feature of the insert. The ANSI Standard includes items now commonly used and facilitates identification of items not in common use. Identification con- sists of up to ten positions; each position defines a characteristic of the insert as shown below: 1 2 3 4 5 6 7 8 a 9 a 10 a T N M G 5 4 3 A a Eighth, Ninth, and Tenth Positions are used only when required. 1) Shape: The shape of an insert is designated by a letter: R for round; S, square; T, trian gle; A, 85 ° parallelogram; B, 82 ° parallelogram; C, 80 ° diamond; D, 55 ° diamond; E, 75 ° diamond; H, hexagon; K, 55 ° parallelogram; L, rectangle; M, 86 ° diamond; O, octagon; P, pentagon; V, 35 ° diamond; and W, 80 ° trigon. 2) Relief Angle (Clearances): The second position is a letter denoting the relief angles: N for 0 ° ; A, 3 ° ; B, 5 ° ; C, 7 ° ; P, 11 ° ; D, 15 ° ; E, 20 ° ; F, 25 ° ; G, 30 ° ; H, 0 ° & 11 ° ∗ ; J, 0 ° & 14 ° * ; K, 0 ° & 17 ° * ; L, 0 ° & 20 ° * ; M, 11 ° & 14 ° * ; R, 11 ° & 17 ° * ; S, 11 ° & 20 ° * . When mounted on a holder, the actual relief angle may be different from that on the insert. 3) Tolerances: The third position is a letter and indicates the tolerances controlling the indexability of the insert. Tolerances specified do not imply the method of manufacture.
Tolerance (± from nominal)
Tolerance (± from nominal)
Inscribed Circle, Inch
Thickness, Inch
Inscribed Circle, Inch 0.002–0.005 0.002–0.005 0.0005
Thickness, Inch
Symbol
Symbol
A B C D E F G
0.001 0.001 0.001 0.001 0.001 0.0005 0.001
0.001 0.005 0.001 0.005 0.001 0.001 0.005
H K J
0.001 0.001 0.001 0.001 0.005 0.005 0.001
L 0.002–0.005 M 0.002–0.004 a U 0.005–0.010 a
N
0.002–0.004 a
a Exact tolerance is determined by size of insert. See ANSI B212.12. 4) Type: The type of insert is designated by a letter: A, with hole; B, with hole and coun tersink; C, with hole and two countersinks; F, chip grooves both surfaces, no hole; G, same as F but with hole; H, with hole, one countersink, and chip groove on one rake surface; J, with hole, two countersinks and chip grooves on two rake surfaces; M, with hole and chip groove on one rake surface; N, without hole; Q, with hole and two countersinks; R, without hole but with chip groove on one rake surface; T, with hole, one countersink, and chip groove on one rake face; U, with hole, two countersinks, and chip grooves on two rake faces; and W, with hole and one countersink. Note: a dash may be used after * Second angle is secondary facet angle, which may vary by ± 1 ° .
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