Machinery's Handbook, 31st Edition
INDEXABLE INSERTS 841 position 4 to separate the shape-describing portion from the following dimensional description of the insert and is not to be considered a position in the standard description. 5) Size: The size of the insert is designated by a one- or two-digit number. For regular polygons and diamonds, insert size is the number of eighths of an inch in the nominal size of the inscribed circle, and will be a one- or two-digit number when the number of eighths is a whole number. It will be a two-digit number, including one decimal place, when it is not a whole number. Rectangular and parallelogram inserts require two digits: the first digit indicates the number of eighths of an inch width and the second digit the number of quarters of an inch length. 6) Thickness: The thickness is designated by a one- or two-digit number, which indicates the number of sixteenths of an inch in the thickness of the insert. Thickness is a one-digit number when the number of sixteenths is a whole number; it is a two-digit number carried to one decimal place when the number of sixteenths of an inch is not a whole number. 7) Cutting Point Configuration: The cutting point, or nose radius, is designated by a number representing 1 ⁄ 64 ths of an inch; a flat at the cutting point or nose, is designated by a letter: 0 for sharp corner, 0.002 inch max. radius; 0.2 for 0.004 radius; 0.3 for 0.008 radius; 1, 1 ⁄ 64 inch radius; 2, 1 ⁄ 32 inch radius; 3, 3 ⁄ 64 inch radius; 4, 1 ⁄ 16 inch radius; 5, 5 ⁄ 64 inch radius; 6, 3 ⁄ 32 inch radius; 7, 7 ⁄ 64 inch radius; 8, 1 ⁄ 8 inch radius; X, any other radius; A, square insert with 45 ° chamfer; D, square insert with 30 ° chamfer; E, square insert with 15 ° chamfer; F, square insert with 3 ° chamfer; K, square insert with 30 ° double chamfer; L, square insert with 15 ° double chamfer; M, square insert with 3 ° double chamfer; N, truncated triangle insert; and P, flatted corner triangle insert. 8) Special Cutting Point Definition: The eighth position, if it follows a letter in the 7th position, is a number indicating the number of 1 ⁄ 64 ths of an inch in the primary facet length measured parallel to the edge of the facet. 9) Hand: R, right; L, left; to be used when required in ninth position. 10) Other Conditions: Position ten defines special conditions (such as edge treatment, surface finish): A, honed, 0.0005 to less than 0.003 inch (0.0127 to 0.0762 mm); B, honed, 0.003 to less than 0.005 inch (0.0762 to 0.127 mm); C, honed, 0.005 to less than 0.007 inch (0.127 to 0.178 mm); J, polished, 4 µ inch (0.1016 µ m) arithmetic average (AA) on rake surfaces only; T, chamfered, manufacturer’s standard negative land, rake face only. Indexable Insert Tool Holders.— Indexable insert tool holders are made from a good grade of steel which is heat treated to a hardness of 44 to 48 RC (Rockwell C scale) for most normal applications. Accurate pockets that serve to locate the insert in position and to provide surfaces against which the insert can be clamped are machined in the ends of tool holders. A cemented carbide seat usually is provided and is held in the bottom of the pocket by a screw or by the clamping pin, if one is used. The seat is necessary to provide a flat bearing surface upon which the insert can rest and, in so doing, it adds materially to the ability of the insert to withstand the cutting load. The seating surface of the holder may provide a positive-, negative-, or a neutral-rake orientation to the insert when it is in posi- tion on the holder. Holders, therefore, are classified as positive, negative, or neutral rake. Four basic methods are used to clamp the insert on the holder: 1) Clamping, usually top clamping; 2) Pin-lock clamping; 3) Multiple clamping using a clamp, usually a top clamp, and a pin lock; and 4) Clamping the insert with a machine screw. All top clamps are actuated by a screw that forces the clamp directly against the insert. When required, a cemented carbide, plate-type chipbreaker is placed between the clamp and the insert. Pin-lock clamps require an insert having a hole: the pin acts against the walls of the hole to clamp the insert firmly against the seating surfaces of the holder. Multiple or combination clamping, simultaneously using both a pin-lock and a top clamp, is recommended when taking heavier or interrupted cuts. Holders are available on which all the above-mentioned methods of clamping may be used. Other holders are made with only a top clamp or a pin lock. Screw-on type holders use a machine screw to hold the
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