Pitch Diameter Table FOR NOS. 575 AND 585 SCREW THREAD MICROMETERS "V" STANDARD THREAD FORM p h' Fr Fc 29º American St andard Acme Screw Thread Dimensions Caliper Reading or Pitch Diameter for "V" Threads = D - .866 N p = 1 n Fc = .3707 n K = minus p Kr = D minus 2h' FOR 10 OR FEWER THREADS PER INCH h' = P plus .010 2 Fr = .3707 minus .0052 n T = D plus .020 FOR MORE THAN 10 THREADS PER INCH h' = P plus .005 2 Fr = .3707 minus .0026 n T = D plus .010 h = Basic depth of thread Fc = Width of flat at crest of thread Kr = Minor diameter of screw h' = Depth of thread with clearance Fr = Width of flat at bottom of space D = Major diameter of screw K = Tap drill n = Number of threads per inch T = Major diameter of tap Basic minor diameter of nut p = Pitch of thread Diameter (in) Threads per Inch Caliper Reading or Pitch Diameter Single Depth of Thread Diameter (in)* Threads per Inch Caliper Reading or Pitch Diameter Single Depth of Thread D N D – .866 .866 N D N D – .866 .866 N N N Note: As there is no standard of diameter for the finer pitches, this column is left blank. 64 — .0135 1/4 24 .2139 .0361 62 — .0140 1/4 20 .2067 .0433 60 — .0144 5/16 20 .2692 .0433 58 — .0149 5/16 18 .2644 .0481 56 — .0155 3/8 18 .3269 .0481 54 — .0161 3/8 16 .3209 .0541 52 — .0167 7/16 16 .3834 .0541 50 — .0173 7/16 14 .3756 .0619 48 — .0180 1/2 14 .4381 .0619 46 — .0188 1/2 13 .4334 .0666 44 — .0197 1/2 12 .4278 .0722 42 — .0206 9/16 14 .5006 .0619 40 — .0217 9/16 12 .4903 .0722 38 — .0228 5/8 11 .5463 .0787 36 — .0241 5/8 10 .5384 .0866 34 — .0255 11/16 10 .6009 .0866 32 — .0271 3/4 10 .6634 .0866 30 — .0289 7/8 9 .7788 .0962 28 — .0309 1 8 .8918 .1082 26 — .0333 1-1/8 8 1.0168 .1082 — — — 1-1/4 7 1.1263 .1237 — — — 1-1/2 6 1.3557 .1443 * These figures give the outside diameter for screws with threads cut theoretically sharp. As it is not practical to make these threads sharp, the outside diameter will measure less than the figures given, the pitch diameter remaining the same. Threads per inch (n) Depth of Thread with Clearance (h') Flat at Top of Thread (Fc) Flat at Bottom of Space (Fr) Space at Top of Thread Thickness at Root of Thread 1 .5100 .3707 .3655 .6293 .6345 1-1/3 .3850 .2780 .2728 .4720 .4772 2 .2600 .1854 .1802 .3146 .3198 3 .1767 .1236 .1184 .2097 .2149 4 .1350 .0927 .0875 .1573 .1625 5 .1100 .0741 .0689 .1259 .1311 6 .0933 .0618 .0566 .1049 .1101 7 .0814 .0530 .0478 .0899 .0951 8 .0725 .0463 .0411 .0787 .0839 9 .0655 .0412 .0360 .0699 .0751 10 .0600 .0371 .0319 .0629 .0681 12 .0467 .0309 .0283 .0524 .0550 14 .0407 .0265 .0239 .0449 .0475 16 .0363 .0232 .0206 .0393 .0419 588 R eference T ables