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Recommended Drill Bit Sizes for Taps and Forming Taps

Drill Bit Sizes for Taps:

 

Drill Bit Sizes for Forming Taps:

 

ISO METRIC THREAD

Internal thread Tap drill bit diameter according to DIN 336
[mm]
Thread designation Internal diameter [mm]
Tolerance class Size range
min max
M 1 5H 0,729 0,785 0,75
M 1,1 5H 0,829 0,885 0,85
M 1,2 5H 0,929 0,985 0,95
M 1,4 5H 1,075 1,142 1,1
M 1,6 6H 1,221 1,321 1,25
M 1,8 6H 1,421 1,521 1,45
M 2 6H 1,567 1,679 1,6
M 2,2 6H 1,713 1,838 1,75
M 2,5 6H 2,013 2,138 2,05
M 3 6H 2,459 2,599 2,5
M 3,5 6H 2,85 3,01 2,9
M 4 6H 3,242 3,422 3,3
M 4,5 6H 3,688 3,878 3,7
M 5 6H 4,134 4,334 4,2
M 6 6H 4,917 5,153 5
M 7 6H 5,917 6,153 6
M 8 6H 6,647 6,912 6,8
M 9 6H 7,647 7,912 7,8
M 10 6H 8,376 8,676 8,5
M 11 6H 9,376 9,676 9,5
M 12 6H 10,106 10,441 10,2
M 14 6H 11,835 12,21 12
M 16 6H 13,835 14,21 14
M 18 6H 15,294 15,744 15,5
M 20 6H 17,294 17,744 17,5
M 22 6H 19,294 19,744 19,5
M 24 6H 20,752 21,252 21
M 27 6H 23,752 24,252 24
M 30 6H 26,211 26,771 26,5
M 33 6H 29,211 29,771 29,5
M 36 6H 31,67 32,27 32
M 39 6H 34,67 35,27 35
M 42 6H 37,129 37,799 37,5
M 45 6H 40,129 40,799 40,5
M 48 6H 42,587 43,297 43
M 52 6H 46,587 47,297 47
M 56 6H 50,046 50,796 50,5

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METRIC FINE THREAD

Internal thread Tap drill bit diameter according to DIN 336
[mm]
Thread designation Internal diameter [mm]
Tolerance class Size range
min max
M 1x0,2 4H 0,783 0,821 0,8
M 1,1x0,2 4H 0,883 0,921 0,9
M 1,2x0,2 4H 0,983 1,021 1
M 1,4x0,2 4H 1,183 1,221 1,2
M 1,4x0,25 5H 1,129 1,185 1,15
M 1,6x0,2 4H 1,383 1,421 1,4
M 1,8x0,2 4H 1,583 1,621 1,6
M 2x0,25 5H 1,729 1,785 1,75
M 2,2x0,25 5H 1,929 1,985 1,95
M 2,5x0,35 6H 2,121 2,221 2,15
M 3x0,35 6H 2,621 2,721 2,65
M 3,5x0,35 6H 3,121 3,221 3,15
M 4x0,5 6H 3,459 3,599 3,5
M 4,5x0,5 6H 3,959 4,099 4
M 5x0,5 6H 4,459 4,599 4,5
M 5,5x0,5 6H 4,959 5,099 5
M 6x0,75 6H 5,188 5,378 5,2
M 7x0,75 6H 6,188 6,378 6,2
M 8x0,75 6H 7,188 7,378 7,2
M 8x1 6H 6,917 7,153 7
M 9x0,75 6H 8,188 8,378 8,2
M 9x1 6H 7,917 8,153 8
M 10x0,75 6H 9,188 9,378 9,2
M 10x1 6H 8,917 9,153 9
M 10x1,25 6H 8,647 8,912 8,8
M 11x0,75 6H 10,188 10,378 10,2
M 11x1 6H 9,917 10,153 10
M 12x1 6H 10,917 11,153 11
M 12x1,25 6H 10,647 10,912 10,8
M 12x1,5 6H 10,376 10,676 10,5
M 14x1 6H 12,917 13,153 13
M 14x1,25 6H 12,647 12,912 12,8
M 14x1,5 6H 12,376 12,676 12,5
M 15x1 6H 13,917 14,153 14
M 15x1,5 6H 13,376 13,676 13,5
M 16x1 6H 14,917 15,153 15
M 16x1,5 6H 14,376 14,676 14,5
M 17x1 6H 15,917 16,153 16
M 17x1,5 6H 15,376 15,676 15,5
M 18x1 6H 16,917 17,153 17
M 18x1,5 6H 16,376 16,676 16,5
M 18x2 6H 15,835 16,21 16
M 20x1 6H 18,917 19,153 19
M 20x1,5 6H 18,376 18,676 18,5
M 20x2 6H 17,835 18,21 18
M 22x1 6H 20,917 21,153 21
M 22x1,5 6H 20,376 20,676 20,5
M 22x2 6H 19,835 20,21 20
M 24x1 6H 22,917 23,153 23
M 24x1,5 6H 22,376 22,676 22,5
M 24x2 6H 21,835 22,21 22
M 25x1 6H 23,917 24,153 24
M 25x1,5 6H 23,376 23,676 23,5
M 25x2 6H 22,835 23,21 23
M 26x1,5 6H 24,376 24,676 24,5
M 27x1 6H 25,917 26,153 26
M 27x1,5 6H 25,376 25,676 25,5
M 27x2 6H 24,835 25,21 25
M 28x1 6H 26,917 27,153 27
M 28x1,5 6H 26,376 26,676 26,5
M 28x2 6H 25,835 26,21 26
M 30x1 6H 28,917 29,153 29
M 30x1,5 6H 28,376 28,676 28,5
M 30x2 6H 27,835 28,21 28
M 30x3 6H 26,752 27,252 27
M 32x1,5 6H 30,376 30,676 30,5
M 32x2 6H 29,835 30,21 30
M 33x1,5 6H 31,376 31,676 31,5
M 33x2 6H 30,835 31,21 31
M 33x3 6H 29,752 30,252 30
M 35x1,5 6H 33,376 33,676 33,5
M 36x1,5 6H 34,376 34,676 34,5
M 36x2 6H 33,835 34,21 34
M 36x3 6H 32,752 33,252 33
M 38x1,5 6H 36,376 36,676 36,5
M 39x1,5 6H 37,376 37,676 37,5
M 39x2 6H 36,835 37,21 37
M 39x3 6H 35,752 36,252 36
M 40x1,5 6H 38,376 38,676 38,5
M 40x2 6H 37,835 38,21 38
M 40x3 6H 36,752 37,252 37
M 42x1,5 6H 40,376 40,676 40,5
M 42x2 6H 39,835 40,21 40
M 42x3 6H 38,752 39,252 39
M 42x4 6H 37,67 38,27 38
M 45x1,5 6H 43,376 43,676 43,5
M 45x2 6H 42,835 43,21 43
M 45x3 6H 41,752 42,252 42
M 45x4 6H 40,67 41,27 41
M 48x1,5 6H 46,376 46,676 46,5
M 48x2 6H 45,835 46,21 46
M 48x3 6H 44,752 45,252 45
M 48x4 6H 43,67 44,27 44
M 50x1,5 6H 48,376 48,676 48,5
M 52x1,5 6H 50,376 50,676 50,5

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 METRIC FINE THREAD
PRINCIPLE FOR CALCULATING DRILL BIT DIAMETER

For the pitch F of the drill = nominal F of the thread minus given value
0,2 0,2
0,25 0,25
0,35 0,35
0,5 0,5
0,75 0,8
1 1
1,5 1,5
2 2
3 3
4 4

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AMERICAN UNIFIED COARSE THREAD UNC

Thread designation Internal diameter for tolerance 2B [mm] Tap drill bit diameter according to DIN 336
[mm]
min max
1-64 UNC 1,425 1,582 1,55
2-56 UNC 1,694 1,872 1,85
3-48 UNC 1,941 2,146 2,1
4-40 UNC 2,156 2,385 2,35
5-40 UNC 2,487 2,697 2,65
6-32 UNC 2,642 2,896 2,85
8-32 UNC 3,302 3,531 3,5
10-24 UNC 3,683 3,962 3,9
12-24 UNC 4,343 4,597 4,5
1/4-20 UNC 4,976 5,268 5,1
5/16-18 UNC 6,411 6,734 6,6
3/8-16 UNC 7,805 8,164 8
7/16-14 UNC 9,149 9,55 9,4
1/2-13 UNC 10,584 11,013 10,8
9/16-12 UNC 11,996 12,456 12,2
5/8-11 UNC 13,376 13,868 13,5
3/4-10 UNC 16,299 16,833 16,5
7/8-9 UNC 19,169 19,748 19,5
1-8 UNC 21,963 22,598 22,25
1_1/8-7 UNC 24,648 25,349 25
1_1/4-7 UNC 27,823 28,524 28
1_3/8-6 UNC 30,343 31,12 30,75
1_1/2-6 UNC 33,518 34,295 34
1_3/4-5 UNC 38,951 39,814 39,5
2-4_1/2 UNC 44,689 45,598 45

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AMERICAN UNIFIED FINE THREAD UNF

Thread designation Internal diameter for tolerance 2B [mm] Tap drill bit diameter according to DIN 336
[mm]
min max
1-72 UNF 1,473 1,613 1,55
2-64 UNF 1,755 1,913 1,85
3-56 UNF 2,024 2,197 2,15
4-48 UNF 2,271 2,459 2,4
5-44 UNF 2,55 2,741 2,7
6-40 UNF 2,819 3,023 2,95
8-36 UNF 3,404 3,607 3,5
10-32 UNF 3,962 4,166 4,1
12-28 UNF 4,496 4,724 4,6
1/4-28 UNF 5,367 5,58 5,5
5/16-24 UNF 6,792 7,038 6,9
3/8-24 UNF 8,379 8,626 8,5
7/16-20 UNF 9,738 10,03 9,9
1/2-20 UNF 11,326 11,618 11,5
9/16-18 UNF 12,761 13,084 12,9
5/8-18 UNF 14,348 14,671 14,5
3/4-16 UNF 17,33 17,689 17,5
7/8-14 UNF 20,262 20,663 20,4
1-12 UNF 23,109 23,569 23,25
1_1/8-12 UNF 26,284 26,744 26,5
1_1/4-12 UNF 29,459 29,919 29,5
1_3/8-12 UNF 32,634 33,094 32,75
1_1/2-12 UNF 35,809 36,269 36

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WHITWORTH THREAD BSW

Thread designation Internal diameter [mm] Tap drill bit diameter
[mm]
min max
BSW 1/16 - - 1,2
BSW 3/32 - - 1,9
BSW 1/8 - - 2,5
BSW 5/32 - - 3,2
BSW 3/16 - - 3,6
BSW 7/32 - - 4,5
BSW 1/4 4,744 5,224 5,1
BSW 5/16 6,151 6,661 6,5
BSW 3/8 7,512 8,052 7,9
BSW 7/16 8,809 9,379 9,25
BSW 1/2 10,015 10,61 10,5
BSW 5/8 12,948 13,598 13,5
BSW 3/4 15,831 16,538 16,5
BSW 7/8 18,647 19,411 19,25
BSW 1 21,375 22,185 22
BSW 1_1/8 23,976 24,879 24,75
BSW 1_1/4 27,151 28,054 28
BSW 1_3/8 29,558 30,555 30,5
BSW 1_1/2 32,733 33,73 33,5
BSW 1_5/8 34,834 35,921 35,5
BSW 1_3/4 38,009 39,096 39
BSW 2 43,643 44,823 44,5
BSW 2_1/4 49,1 50,42 50
BSW 2_1/2 55,45 56,77 57
BSW 2_3/4 60,648 62,108 61
BSW 3 66,699 68,459 68

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WHITWORTH PIPE THREAD (Rp)

Thread designation Internal diameter [mm] Tap drill bit diameter according to DIN 336
[mm]
min max
Rp 1/16 6,49 6,632 6,55
Rp 1/8 8,495 8,637 8,6
Rp 1/4 11,341 11,549 11,5
Rp 3/8 14,846 15,054 15
Rp 1/2 18,489 18,773 18,75
Rp 3/4 23,975 24,259 24
Rp 1 30,111 30,471 30,25
Rp 11/4 38,772 39,132 39
Rp 11/2 44,665 45,025 44,85
Rp 2 56,476 56,836 56,5

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BRITISH STANDARD PIPE THREAD (BSP) ACCORDING TO DIN 259 AND DIN-ISO 228

Thread designation Internal diameter [mm] Tap drill bit diameter according to DIN 336
[mm]
min max
G 1/16 6,561 6,843 6,8
G 1/8 8,566 8,848 8,8
G 1/4 11,445 11,89 11,8
G 3/8 14,95 15,395 15,25
G 1/2 18,631 19,172 19
G 5/8 20,587 21,128 21
G 3/4 24,117 24,658 24,5
G 7/8 27,877 28,418 28,25
G 1 30,291 30,931 30,75
G 1_1/8 34,939 35,579 35,5
G 1_1/4 38,952 39,592 39,5
G 1_1/2 44,845 45,485 45,25
G 1_3/4 50,788 51,428 51
G 2 56,656 57,296 57
G 2_1/4 62,752 63,392 63
G 2_1/2 72,226 72,866 73
G 2_3/4 78,576 79,216 79
G 3 84,926 85,566 85

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AMERICAN TAPER PIPE THREAD, 1:16 TAPER

Thread designation Tap drill bit diameter
[mm]
1/8 8,5
1/4 11,1
3/8 14,5
1/2 17,75
3/4 23
1 29
1_1/4 38
1_1/2 44
2 56

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METRIC THREADS FOR FORMING TAPS

Basic principle:
Drill bit diameter = External thread diameter minus 0,5 x pitch
Values given in the table were calculated according to this principle
Thread designation Pitch [mm] Tap drill bit diameter [mm]

Given diameters determine only output values.

Tap drill bit diameter in the case of forming taps depends on:

  • machined material
  • outline of the thread
  • depth of the hole
  • wall thicnkess
  • necessary internal thread diameter

Diameters in parentheses do not belong to normal ISO diameters.

M 1 0,25 0,88
M 1,1 0,25 0,98
M 1,2 0,25 1,08
M 1,4 0,3 1,26
M 1,6 0,35 1,45
(M 1,7) 0,35 1,55
M 1,8 0,35 1,65
M 2 0,4 1,82
M 2,2 0,45 2
(M 2,3) 0,4 2,1
M 2,5 0,45 2,3
(M 2,6) 0,45 2,4
M 3 0,5 2,8
M 3,5 0,6 3,25
M 4 0,7 3,7
M 5 0,8 4,65
M 6 1 5,55
M 7 1 6,5
M 8 1,25 7,4
M 10 1,5 9,3
M 12 1,75 11,2
M 14 2 13,1
M 16 2 15,1

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ISO METRIC FINE THREAD FOR FORMING TAPS

Thread designation Tap drill bit diameter [mm]
M 4x0,5 3,8
M 5x0,5 4,8
M 6x0,5 5,8
M 8x0,5 7,8
M 6x0,75 5,65
M 8x0,75 7,65
M 10x0,75 9,65
M 8x1 7,55
M 10x1 9,55
M 12x1 11,55
M 14x1 13,55
M 16x1 15,55
M 18x1 17,55
M 12x1,5 11,3
M 14x1,5 13,3
M 16x1,5 15,3
M 18x1,5 17,3
M 20x1,5 19,3

? Return

 

AMERICAN UNIFIED COARSE THREAD UNC FOR FORMING TAPS

Thread designation Pitch [mm] Tap drill bit diameter [mm]
2-56 UNC 0,454 1,97
3-48 UNC 0,529 2,26
4-40 UNC 0,635 2,55
5-40 UNC 0,635 2,87
6-32 UNC 0,794 3,15
8-32 UNC 0,794 3,8
10-24 UNC 1,058 4,3
12-24 UNC 1,058 5
1/4-20 UNC 1,27 5,75
5/16-18 UNC 1,411 7,25
3/8-16 UNC 1,588 8,75

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AMERICAN UNIFIED FINE THREAD UNF FOR FORMING TAPS

Thread designation Pitch [mm] Tap drill bit diameter [mm]
4-48 UNF 0,529 2,6
5-44 UNF 0,577 2,9
6-40 UNF 0,635 3,2
8-36 UNF 0,706 3,85
10-32 UNF 0,794 4,45
12-28 UNF 0,907 5,05
1/4-28 UNF 0,907 5,9
5/16-24 UNF 1,058 7,45
3/8-24 UNF 1,058 9

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BRITISH STANDARD PIPE THREAD (BSP) FOR FORMING TAPS

Thread designation Pitch [mm] Tap drill bit diameter [mm]
G 1/16 0,907 7,3
G 1/8 0,907 9,3
G 1/4 1,337 12,5
G 3/8 1,337 16
G 1/2 1,814 20,1

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