Общий каталог Widia 2017 - страница 1802

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Technical Information Ground Thread Tap Limits In addition to the nominal size and pitch of a tap, there is another Figure 1 Illustrates the numbering system and the .0005" diameter important dimensional factor to be considered when selecting a increment separation between successive limits. Because ground thread tap for a given job. This factor is the pitch diameter the starting point is basic pitch diameter, dividing the limit tap limit, “H” and “L”. “H” represents (high) above basic pitch number by two establishes, in thousandths of an inch, the diameter; “L” (low) is below basic pitch diameter. Tap limits have amount the maximum tap pitch diameter is above basic been established to provide a choice in the selection of the tap size in the “H” series and the amount the minimum tap pitch best suited to produce the class of thread desired. diameter is under basic in the “L” series. Figure 2 Illustrates the positioning of the tap limits in relation to the various classes of threads for a 1/4–20 size. Figure 1 .0050 .0050 H10 .0045 This chart shows the .0045 method of designating limits.0040and does not indicateavailable taps in anyH9 .0040 particular size. H8 .0035 .0035 H7 .0030 .0030 H6 .0025 H6 .0025 H5 .0020 H5 .0020 H4 .0015 H4 .0015 H3 .0010 .0010 H2 .0005 .0005 basic H1 basic P.D. L1.0005 For sizes from 1–1-1/2" P.D.For taps through 1" inclusive, 8 TPI and finerinclusive, 6 TPI and finer Figure 2 Class of Thread – 1/4–20 UNC and NC .2255 .2255 .2245 .2248 .2245 tap limits.2235 tapping hole limits .2235 .2225 .2225 .2248 .2215 .2215 1B .2211 .2211 .2205 H5 .2205 2B TOL.0005 .2201 .2195 H3 2 3B .21953 H2 TOL.0005 .2185 H1 TOL.0005 TOL TOL TOL TOL TOL .2185 basic TOL.0005 .0073 .0049 .0036 .0036 .0026 .2175P.D. TOL.0005 .2175 L1 .2165 .2165 Y98 widia.com Technical Information