Steve s Table of Screw Threads and Tap Drill Sizes. Compiled by Stephen G. Wellcome

Transcription

1 Steve s Table of Screw Threads and Sizes Compiled by Stephen G. Wellcome Copyright Stephen G. Wellcome 2001 All Rights Reserved. This document may be copied and printed, with inclusion of author and copyright acknowledgement, for personal non-commercial use only. 1

2 Introduction to the Tables These tables present a comprehensive list of British Association (BA), British Standard Fine (BSF), British Standard Whitworth (BSW), ISO Metric (), National Coarse (NC), and National Fine (NF) screw threads together with recommended tap drill sizes. As you probably know, a tapping hole that gives as little as 55% thread will still yield threads that are about as strong as the bolt itself. A tapping hole that gives a larger percentage of thread will be proportionally harder to tap with little actual benefit. A tapping hole giving about 75% thread is generally regarded as a good compromise, giving a suitable margin of safety while still being relatively easy to tap. The actual choice of tapping hole size depends upon the particular situation. In some cases, a higher percentage of thread may be desirable and in some cases a lower percentage may be desirable. For example, if you are tapping a thin piece of material that will receive only a few threads, a higher percentage of thread may be advisable. On the other had, if you are tapping a hole that is quite long relative to its diameter, even a 55% thread may be satisfactory. To assist in choosing a tap drill other than the one recommended for average conditions, the tables below give a tapping hole size range for each thread showing the theoretical hole diameter that will yield 65% thread, 75% thread, and 85% thread. You can, if the situation warrants it, choose a tap drill based on these figures to yield the percentage thread required. You should remember that drills typically cut slightly oversize, so a drill for a hole diameter to yield, say, a 75% thread will in actuality produce a hole yielding a slightly lesser percentage of thread. According to a chart published by the Greenfield & Die Company, a #56 drill may be expected to cut about.0015 oversize, while a #7 drill may be expected to cut about.004 oversize and a 1/2 drill about.005 oversize. One can therefore expect the actual percentage of thread to be about 10% less than theoretical for a 0-80 thread, 6% less for a 1/4-20 thread, 5% less for a 1/2-13 thread, and 4% less for a 1-8 thread. You can, if you want, figure out the theoretical hole diameter for any thread percentage using the following formula: Hole Diameter = Bolt Diameter - 2 x K x x Percentage K =.6000 for BA threads K =.6403 for BSF and BSW threads K =.6134 for ISO Metric threads K =.6495 for NC and NF threads For example, if you want to find what theoretical tapping hole diameter will yield an 80% thread with a 2BA tap, the numbers (in inches) are:.1544 = Hole Diameter = x.6 x.0319 x.80 Checking the table, we see that.1544 is exactly halfway between the figures given for a 75% 2BA thread (.1563) and an 85% 2BA thread (.1525), as one might expect. Metric dimensions in the tables are designated with a small m except for those in the columns and, which are assumed to be metric in all cases. The metric thread pitches are designated Mc (metric coarse) or Mf (metric fine) as they are shown in a table on page 1357 of the 21st edition of Machinery s Handbook. Four thread pitches (M1.0x.20, M1.1x.20, M1.2x.20, and M1.4x.20) that appear in the tables below do not appear in the table in Machinery s Hand- 2

3 book, so they are not identified as either coarse or fine. It looks as though they would probably be classed as Mf. For any given bolt diameter, there seems to be only one coarse metric thread pitch designated, but there may be several fine thread pitches. For example, there is only Mc12.x1.75, but there are Mf12.x1.5, Mf12.x1,25, and Mf12.x1.0. The is merely a guess. Use your own best judgement. The tap drills listed are English sizes (fractional, number, or letter) because it s obvious from the metric dimensions in the column what an appropriate metric tap drill would be. It s not so obvious what an appropriate fractional, number, or letter tap drill would be. In a few cases there is no obviously suitable English-dimension tap drill for a particular thread, so the two closest (larger and smaller) sizes are given. If you need to tap one of those threads, you may want to bore the hole to tapping size or use a metric drill. Other Useful Stuff The formula for the diameter of a number-size screw is: D =.013 x N The pitch of a 0 BA screw is 1.00, by definition. The pitch of each size smaller BA screw is.9 times the pitch of the next larger. The pitch of an N BA screw is therefore.9 N. If You Find An Error... Please send to sas@ma.ultranet.com so I can fix it. Or, if you have some werid thread you d like added to the tables, send and I ll see about putting it in an updated version. 3

4 Table 1: Thread Sizes Sorted By m m m m m m m m m Dia. BA BSF/BSW NC/NF 16BA m m m M1.0x m m m M1.1x m m m} M1.2x m m m M1.4x m m m Mf1.6x m m m Mf1.8x m m m 15BA m m m m m m {72} {67} { {60} {56} {54} {52} {70} {71} 4

5 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF 14BA m m m Mc1.0x m m m Mc1.1x m m m Mc1.2x m m m 13BA m m m Mf2.0x m m m Mf2.2x m m m m m m 12BA m m m m m m {68} {68} {65} {62} {62} {50} {47} {63} {59} {63} 5

6 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF Mc1.4x m m m 11BA m m m 0-80NF m m m 1/ m m m Mc1.6x m m m 10BA m m m Mc1.8x m m m Mf2.5x m m m Mf3.0x m m m Mf3.5x m m m {57} {56} {3/64} {B} {55} {54} {53} {44} {36} {1/8} 6

7 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF 1-72NF m m m 9BA m m m 1-64NC m m m 2-64NF m m m Mc2.0x m m m 1/16-60BSW m m m 8BA m m m Mc2.2x m m {50} Mc2.5x m m m 2-56NC m m m {53} {1/16} {53} {50} {52} {56} {50} m {45} {51} 7

8 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF 3-56NF m m m m m m 7BA m m m Mc3.0x m m m Mf4.0x m m m Mf4.5x m m m Mf5.0x m m m Mf5.5x m m m 3/32-48BSW m m m 3-48NC m m m {46} {17} {46} {39} {28} {21} {16} {8} {49} {5/64} 8

9 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF 4-48NF m m m m m m 6BA m m m 5-44NF m m m 5BA m m m Mc3.5x m m m 4-40NC m m m 5-40NC m m m 1/8-40BSW m m m 6-40NF m m m {42} {32} {42} {37} {37} {32} {43} {39} {40} {33} 9

10 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF 5/ m m m 3/ m m m 7/ m m m 1/ m m m 5/ m m m 3/ m m m 7/ m m m 1/ m m m 4BA m m m Mc4.0x m m m {30} {20} {9} {1} {L} {S} {Z} {31/64} {15/32} {32} {30} 10

11 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF 8-36NF m m m 3BA m m m Mc4.5x m m m Mf6.0x m m m Mf7.0x m m m Mf8.0x m m m Mf9.0x m m m Mf10.x m m m Mf11.x m m m 6-32NC m m m {29} {29} {25} {4} {D} {L} {21/64} {U} {Y} {36} 11

12 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF 5/32-32BSW m m m 8-32NC m m m 3/16-32BSF m m m 10-32NF m m m 1/4-32NEF m m m 9/ m m m 5/16-32NEF m m m 3/8-32NEF m m m Mc5.0x m m m 2BA m m m {1/8} {29} {22} {21} {7/32} {1/4} {9/32} {11/32} {19} {22} 12

13 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF 1BA m m m 12-28NF m m m 7/32-28BSF m m m 1/4-28NF m m m 7/16-28NEF m m m 1/2-28NEF m m m 1/4-26BSF m m m 9/32-26BSF m m m 0BA m m m Mc6.0x m m m {16} {15} {14} {3} {Y} {15/32} {4} {B} {7} {7} 13

14 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF Mc7.0x m m m Mf8.0x m m m Mf9.0x m m m Mf10.x m m m Mf11.x m m m Mf12.x m m m Mf14.x m m m Mf15.x m m m Mf16.x m m m Mf17.x m m m {B} {J} {O} {T} {X} {7/16} {33/64} {35/64} {9/16} {19/32} {41/64} {5/8} 14

15 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF Mf18.x m m m Mf20.x m m m Mf22.x m m m Mf24.x m m m Mf25.x m m m 3/16-24BSW m m m 10-24NC m m m 12-24NC m m m 14-24NF m m m 5/16-24NF m m m {43/64} {3/4} {53/64} {29/32} {61/64} {15/16} {27} {25} {17} {7} {I} 15

16 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF 3/8-24NF m m m 9/16-24NEF m m m 5/8-24NEF m m m 11/16-24NEF m m m 5/16-22BSF m m m Mc8.0x m m m Mc9.0x m m m Mf10.x m m m Mf12.x m m m Mf14.x m m m {Q} {17/32} {33/64} {19/32} {37/64} {21/32} {41/64} {H} {H} {N} {S} {27/64} {1/2} 16

17 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF 14-20NC m m m 1/4-20BSW m m m 1/4-20NC m m m 3/8-20BSF m m m 7/16-20NF m m m 1/2-20NF m m m 3/4-20NEF m m m 13/16-20NEF m m m 7/8-20NEF m m m 15/16-20NEF m m m {10} {7} {7} {P} {W} {29/64} {45/64} {49/64} {53/64} {57/64} 17

18 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF 1-20NEF m m m 5/16-18BSW m m m 5/16-18NC m m m 7/16-18BSF m m m 9/16-18NF m m m 5/8-18NF m m m Mc10.x m m m Mc11.x m m m Mf12.x m m m Mf14.x m m m {61/64} {F} {F} {3/8} {33/64} {37/64} {R} {V} {Z} {1/2} 18

19 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF Mf15.x m m m Mf16.x m m m Mf17.x m m m Mf18.x m m m Mf20.x m m m Mf22.x m m m Mf24.x m m m Mf25.x m m m 3/8-16NC m m m 3/8-16BSW m m m {17/32} {37/64} {39/64} {21/32} {47/64} {13/16} {57/64} {15/16} {5/16} {5/16} 19

20 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF 1/2-16BSF m m m 9/16-16BSF m m m 3/4-16NF m m m Mc12.x m m m 7/16-14NC m m m 7/16-14BSW m m m 5/8-14BSF m m m 11/16-14BSF m m m 7/8-14NF m m m 1/2-13NC m m m {7/16} {1/2} {11/16} {Y} {U} {U} {35/64} {39/64} {13/16} {27/64} 20

21 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF Mc14.x m m m Mc16.x m m m Mf18.x m m m Mf20.x m m m Mf22.x m m m Mf24.x m m m Mf25.x m m m 1/ m m m 1/2-12BSW m m m 9/16-12BSW m m m {31/64} {9/16} {41/64} {23/32} {51/64} {7/8} {29/32} {27/64} {27/64} {15/32} 21

22 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF 9/16-12NC m m m 3/4-12BSF m m m 13/16-12BSF m m m 1-12NF m m m 5/8-11BSW m m m 11/16-11BSW m m m 7/8-11BSF m m m Mc18.x m m m Mc20.x m m m Mc22.x m m m {31/64} {21/32} {47/64} {59/64} {33/64} {19/32} {25/32} {39/64} {11/16} {49/64} 22

23 Table 1: Thread Sizes Sorted By m m m m m m m m m m Dia. BA BSF/BSW NC/NF 3/4-10NC m m m 3/4-10BSF m m m 13/16-10BSW m m m 1-10BSF m m m 7/8-9BSW m m m 7/8-9NC m m m Mc24.x m m m 1-8BSW m m m 1-8NC m m m m m m {21/32} {41/64} {21/32} {41/64} {23/32} {29/32} {57/64} {49/64} {49/64} {53/64} {7/8} {7/8} {1 3/8} 23

24 Table 1: Thread Sizes Sorted By m Dia. BA BSF/BSW NC/NF m m m {2 1/8} 24

25 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m Dia. BA BSF/BSW NC/NF 16BA m m m m m m 15BA m m m M1.0x m m m 14BA m m m Mc1.0x m m m M1.1x m m m Mc1.1x m m m m m m {72} {71} {70} {67} {68} {68} {64} {65} {63} 25

26 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF m m m M1.2x m m m Mc1.2x m m m 13BA m m m 12BA m m m M1.4x m m m Mc1.4x m m m 11BA m m m 0-80NF m m m 1/16-60BSW m m m {63} {60} {62} {62} {59} {56} {57} {56} {3/64} {56} 26

27 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF Mf1.6x m m m Mc1.6x m m m 10BA m m m Mf1.8x m m m Mc1.8x m m m 1-72NF m m m 1-64NC m m m 9BA m m m Mf2.0x m m m Mc2.0x m m m {54} {55} {54} {52} {53} {53} {53} {1/16} {50} {52} 27

28 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF 2-64NF m m m 2-56NC m m m Mf2.2x m m m 8BA m m m Mc2.2x m m m 3/32-48BSW m m m Mf2.5x m m m Mc2.5x m m m 7BA m m m 3-56NF m m m {50} {51} {47} {50} {50} {49} {44} {45} {46} {46} 28

29 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF 3-48NC m m m 6BA m m m 4-48NF m m m 4-40NC m m m Mf3.0x m m m Mc3.0x m m m 5-44NF m m m 5-40NC m m m 1/8-40BSW m m m 5BA m m m {5/64} {42} {42} {43} {36} {39} {37} {39} {40} {37} 29

30 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF Mf3.5x m m m Mc3.5x m m m m m m 6-40NF m m m 6-32NC m m m 4BA m m m 5/ m m m 5/32-32BSW m m m Mf4.0x m m m Mc4.0x m m m {1/8} {32} {32} {33} {36} {32} {30} {1/8} {28} {30} 30

31 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF 3BA m m m 8-36NF m m m 8-32NC m m m Mf4.5x m m m Mc4.5x m m m 2BA m m m 3/ m m m 3/16-32BSF m m m 3/16-24BSW m m m m m m {29} {29} {29} {21} {25} {22} {20} {22} {27} {17} 31

32 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF 10-32NF m m m 10-24NC m m m Mf5.0x m m m Mc5.0x m m m 1BA m m m 12-28NF m m m 12-24NC m m m Mf5.5x m m m 7/ m m m 7/32-28BSF m m m {21} {25} {16} {19} {16} {15} {17} {8} {9} {14} 32

33 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF Mf6.0x m m m Mc6.0x m m m 0BA m m m 14-24NF m m m 14-20NC m m m 1/ m m m 1/ m m m 1/4-32NEF m m m 1/4-28NF m m m 1/4-26BSF m m m {4} {7} {7} {7} {10} {B} {1} {7/32} {3} {4} 33

34 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF 1/4-20BSW m m m 1/4-20NC m m m Mf7.0x m m m Mc7.0x m m m 9/ m m m 9/32-26BSF m m m 5/ m m m 5/16-32NEF m m m 5/16-24NF m m m 5/16-22BSF m m m {7} {7} {D} {B} {1/4} {B} {L} {9/32} {I} {H} 34

35 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF 5/16-18BSW m m m 5/16-18NC m m m Mf8.0x m m m Mf8.0x m m m Mc8.0x m m m Mf9.0x m m m Mf9.0x m m m Mc9.0x m m m 3/ m m m 3/8-32NEF m m {F} {F} {L} {J} {H} {21/64} {O} {N} {S} {11/32} 35

36 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF 3/8-24NF m m m 3/8-20BSF m m m 3/8-16BSW m m m 3/8-16NC m m m Mf10.x m m m Mf10.x m m m Mf10.x m m m Mc10.x m m m Mf11.x m m m Mf11.x m m m {Q} {P} {5/16} {5/16} {U} {T} {S} {R} {Y} {X} 36

37 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF Mc11.x m m m 7/ m m m 7/16-28NEF m m m 7/16-20NF m m m 7/16-18BSF m m m 7/16-14BSW m m m 7/16-14NC m m m Mf12.x m m m Mf12.x m m m Mf12.x m m m {V} {Z} {Y} {W} {3/8} {U} {U} {7/16} {27/64} {Z} 37

38 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF Mc12.x m m m 1/ m m m 1/2-28NEF m m m 1/2-20NF m m m 1/2-16BSF m m m 1/2-13NC m m m 1/2-12BSW m m m 1/ m m m Mf14.x m m m Mf14.x m m m {Y} {31/64} {15/32} {15/32} {29/64} {7/16} {27/64} {27/64} {27/64} {1/2} {33/64} 38

39 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF Mf14.x m m m Mc14.x m m m 9/16-24NEF m m m 9/16-18NF m m m 9/16-16BSF m m m 9/16-12BSW m m m 9/16-12NC m m m Mf15.x m m m Mf15.x m m m 5/8-24NEF m m m {1/2} {31/64} {17/32} {33/64} {33/64} {1/2} {15/32} {31/64} {35/64} {9/16} {17/32} {19/32} {37/64} 39

40 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF 5/8-18NF m m m 5/8-14BSF m m m 5/8-11BSW m m m Mf16.x m m m Mf16.x m m m Mc16.x m m m Mf17.x m m m Mf17.x m m m 11/16-24NEF m m m 11/16-14BSF m m m {37/64} {35/64} {33/64} {19/32} {37/64} {9/16} {41/64} {5/8} {39/64} {21/32} {41/64} {39/64} 40

41 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF 11/16-11BSW m m m Mf18.x m m m Mf18.x m m m Mf18.x m m m Mc18.x m m m 3/4-20NEF m m m 3/4-16NF m m m 3/4-12BSF m m m 3/4-10BSF m m m 3/4-10NC m m m {19/32} {43/64} {21/32} {41/64} {39/64} {45/64} {11/16} {21/32} {21/32} {41/64} {21/32} {41/64} 41

42 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF Mf20.x m m m Mf20.x m m m Mf20.x m m m Mc20.x m m m 13/16-20NEF m m m 13/16-12BSF m m m 13/16-10BSW m m m Mf22.x m m m Mf22.x m m m Mf22.x m m m {3/4} {47/64} {23/32} {11/16} {49/64} {47/64} {23/32} {53/64} {13/16} {51/64} 42

43 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF Mc22.x m m m 7/8-20NEF m m m 7/8-14NF m m m 7/8-11BSF m m m 7/8-9BSW m m m 7/8-9NC m m m 15/16-20NEF m m m Mf24.x m m m Mf24.x m m m Mf24.x m m m {49/64} {53/64} {13/16} {25/32} {49/64} {49/64} {57/64} {29/32} {57/64} {7/8} 43

44 Table 2: Thread Sizes Sorted By Diameter m m m m m m m m m m Dia. BA BSF/BSW NC/NF Mc24.x m m m Mf25.x m m m Mf25.x m m m Mf25.x m m m 1-20NEF m m m 1-12NF m m m 1-10BSF m m m 1-8BSW m m m 1-8NC m m m m m m {53/64} {61/64} {15/16} {15/16} {29/32} {61/64} {59/64} {29/32} {57/64} {7/8} {7/8} {1 3/8} 44

45 Table 2: Thread Sizes Sorted By Diameter m Dia. BA BSF/BSW NC/NF m m m {2 1/8} 45

46 Wire and Letter Sizes Table 3: Size Size Size Size A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

47 Table 3: Size Size Size Size

48 Table 4: Fractional Eqivalents 1/ / / / / / / / / / / / / / / / / / / / / / / / / / / /

49 Table 4: Fractional Eqivalents 29/ / / / / / / / / / / / / / / / / / / / / / / / / / / / / /

50 Table 4: Fractional Eqivalents 59/ / / / /