Machinery's Handbook, 31st Edition
964 COUNTERBORES AND CARBIDE BORING TOOLS Counterbore Sizes for Hex-Head Bolts and Nuts.— Table 3a, page 1689 , shows the max- imum socket wrench dimensions for standard 1 ⁄ 4 -, 1 ⁄ 2 - and 3 ⁄ 4 -inch drive socket sets. For a given socket size (nominal size equals the maximum width across the flats of nut or bolt head), the dimension K given in the table is the minimum counterbore diameter required to provide socket wrench clearance for access to the bolt or nut. Sintered Carbide Boring Tools.— Industrial experience has shown that the shapes of tools used for boring operations need to be different from those of single-point tools ordinarily used for general applications such as lathe work. Accordingly, Section 5 of American National Standard ANSI B212.1-2002 gives standard sizes, styles and desig- nations for four basic types of sintered carbide boring tools, namely: solid carbide square; carbide-tipped square; solid carbide round; and carbide-tipped round boring tools. In addition to these ready-to-use standard boring tools, solid carbide round and square un- sharpened boring tool bits are provided. Style Designations for Carbide Boring Tools: Table 1 shows designations used to spec ify the styles of American Standard sintered carbide boring tools. The first letter denotes solid (S) or tipped (T). The second letter denotes square (S) or round (R). The side cutting edge angle is denoted by a third letter (A through H) to complete the style designation. Solid square and round bits with the mounting surfaces ground but the cutting edges unsharpened (Table 3) are designated using the same system except that the third letter indicating the side cutting edge angle is omitted. Table 1. American National Standard Sintered Carbide Boring Tools — Style Designations ANSI B212.1-2002 (R2007) Side Cutting Edge Angle E Boring Tool Styles Solid Square (SS) Tipped Square (TS) Solid Round (SR) Tipped Round (TR) Degrees Designation 0 A TSA 10 B TSB 30 C SSC TSC SRC TRC 40 D TSD 45 E SSE TSE SRE TRE 55 F TSF 90 (0 ° Rake) G TRG 90 (10 ° Rake) H TRH Size Designation of Carbide Boring Tools: Specific sizes of boring tools are identified by the addition of numbers after the style designation. The first number denotes the diameter or square size in number of 1 ⁄ 32 nds for types SS and SR and in number of 1 ⁄ 16 ths for types TS and TR. The second number denotes length in number of 1 ⁄ 8ths for types SS and SR. For styles TRG and TRH, a letter “U” after the number denotes a semi-finished tool (cut ting edges unsharpened). Complete designations for the various standard sizes of carbide boring tools are given in Table 2 through Table 7. In the diagrams in the tables, angles shown without tolerance are ± 1 ° . Examples of Tool Designation: The designation TSC-8 indicates a carbide-tipped tool (T); square cross section (S); 30-degree side cutting edge angle (C); and 8 ⁄ 16 or 1 ⁄ 2 inch square size (8). The designation SRE-66 indicates a solid carbide tool (S); round cross section (R); 45-degree side cutting edge angle (E); 6 ⁄ 32 or 3 ⁄ 16 inch diameter (6); and 6 ⁄ 8 or 3 ⁄ 4 inch long (6). The designation SS-610 indicates a solid carbide tool (S); square cross section (S); 6 ⁄ 32 or 3 ⁄ 16 inch square size (6); 10 ⁄ 8 or 1 1 ⁄ 4 inches long (10). It should be noted in this last example that the absence of a third letter (from A to H) indicates that the tool has its mounting surfaces ground but that the cutting edges are unsharpened.
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