Threads, Threads, Threads...

Regardless of the hobby, model railroads, steam engines or any other metal work you will get in contact with threads and threading. When that happens it is necessary to drill a correctly sized core hole to be able to thread the hole using a tap. In other cases it is necessary to make a screw or other outside thread, and then the job must be correct on its outer diameter. The tables below describes precisely this.

Thread Tables

Metric Coarse (M)

Thread Coarse	Pitch	Core dia.(mm)	Core Drill (mm)	Drill for Free holes (mm)
M1	0,25	0,676		1,05
M1,2	0,25	0,876	0,95	1,25
M1,4	0,3	1,010		1,45
M1,6	0,35	1,321	1,25	1,65
M2	0,4	1,679	1,45	2,05
M2,2	0,45	1,838	1,75	2,25
M2,5	0,45	2,138	2,05	2,60
M3	0,5	2,599	2,5	3,10
M3,5	0,6	3,010	2,9	3,60
M4	0,7	3,422	3,3	4,10
M4,5	0,75	3,878	3,8	4,60
M5	0,8	4,334	4,2	5,10
M6	1	5,153	5	6,10
M7	1	6,153	6	7,20
M8	1,25	6,912	6,8	8,20
M9	1,25	7,912	7,8	9,20
M10	1,5	8,676	8,6	10,20
M11	1,5	9,676	9,6	11,20
M12	1,75	10,441	10,3	12,20
M14	2	12,210	12	14,25
M16	2	14,210	14	16,25
M18	2,5	15,744	15,5	18,25
M20	2,5	17,744	17,5	20,25
M22	2,5	19,744	19,5	22,25
M24	3	21,252	21	24,25
M27	3	24,252	24	27,25
M30	3,5	26,771	26,5	30,30
M33	3,5	29,771	29,5	33,30
M36	4	32,270	32	36,30
M39	4	35,270	35	39,30
M42	4,5	37,799	37,5	42,30
M45	4,5	40,799	40,5	45,30
M48	5	43,297	43	48,30
M52	5	47,297	47	52,30

Metric Fine (MF)

Thread Fine	Pitch	Max Core Dia(mm)	Drill for Tap(mm)
MF 3	0,35	2,721	2,7
MF 3,5	0,35	3,221	3,1
MF 4	0,5	3,599	3,5
MF 5	0,5	4,599	4,5
MF 5,5	0,5	5,099	5
MF 6	0,75	5,378	5,2
MF 7	0,75	6,378	6,2
MF 8	0,75	7,378	7,2
MF 8	1,0	7,153	7
MF 9	1,0	8,153	8
MF 10	0,75	9,378	9,2
MF 10	1,0	9,153	9
MF 10	1,25	8,912	8,8
MF 11	1,0	10,153	10
MF 12	1,0	11,153	11
MF 12	1,25	10,912	10,8
MF 12	1,5	10,676	10,5
MF 14	1,0	13,153	13
MF 14	1,25	12,912	12,8
MF 14	1,5	12,676	12,5
MF 15	1,0	14,153	14
MF 15	1,5	13,676	13,5
MF 16	1,0	15,153	15
MF 16	1,5	14,676	14,5
MF 18	1,0	17,153	17
MF 18	1,5	16,676	16,5
MF 18	2,0	16,210	16
MF 20	1,0	19,153	19
MF 20	1,5	18,676	18,5
MF 22	1,0	21,153	21
MF 20	2,0	18,210	18
MF 22	1,5	20,676	20,5
MF 22	2,0	20,210	20
MF 24	1,0	23,153	23
MF 24	1,5	22,676	22,5
MF 24	2,0	22,210	22
MF 25	1,5	23,676	23,5
MF 25	2,0	23,210	23
MF 26	1,5	24,676	24,5
MF 27	1,5	25,676	25,5
MF 27	2,0	25,210	25
MF 28	1,5	26,676	26,5
MF 28	2,0	26,210	26
MF 30	1,5	28,676	28,5
MF 30	2,0	28,210	28
MF 32	1,5	30,676	30,5
MF 32	2,0	30,210	30
MF 33	2,0	31,210	31
MF 35	1,5	33,676	33,5
MF 36	1,5	34,676	34,5
MF 36	2,0	34,210	34
MF 36	3,0	33,252	33

Imperial Coarse (W eller BSW - British Standard Whitworth)

Thread
Coarse Pitch Max Core Dia(mm)
Drill for tap

(mm)

1/16"

60

1,05

3/32"

48

1,95

1/8"

40

2,65

5/32"

32

3,3

3/16"

24

3,9

7/32"

24

4,7

1/4"

20

5,3

5/16"

18

6,7

3/8"

16

8,2

7/16"

14

9,5

1/2"

12

10,7

9/16"

12

12,4

5/8"

11

13,8

3/4"

10

16,75

7/8"

9

19,5

1"

8

22,5

Imperial fine (BSF - British Standard (Whitworth) Fine)

Thread
Coarse Pitch Max Core Dia(mm)
Drill for tap

(mm)

3/16"

32

4,1

7/32"

28

4,8

1/4"

26

5,5

5/16"

22

7,0

3/8"

20

8,4

7/16"

18

10,0

1/2"

16

11,3

9/16"

16

12,9

5/8"

14

14,25

3/4"

12

17,0

7/8"

11

20,0

1"

10

23,0

Imperial Model Engineering (ME)

Thread Pitch Max Core Dia(mm)
Drill for tap

(mm)

1/8"

40

3,3

5/32"

40

3,4

3/16"

40

4,2

7/32"

40

5,0

1/4"

40

5,8

5/16"

32

40

7,2

7,4

3/8"

32

40

8,8

9,0

7/16"

32

40

10,4

10,5

1/2"

32

40

12,0

12,1

British Association (BA)

Thread Pitch Max Core Dia(mm)
Drill for tap

(mm)

0

1,0

5,2

1

0,9

4,6

2

0,81

4,1

3

0,73

3,5

4

0,66

3,1

5

0,59

2,75

6

0,53

2,35

7

0,48

2,1

8

0,43

1,85

9

0,39

1,6

10

0,35

1,45

11

0,31

1,25

12

0,28

1,10

14

0,23

0,82

Unified Coarse (UNC)

Thread Coarse Pitch Max Core Dia(mm)

Drill for tap(mm)

1-64

64

1,55

2-56

56

1,85

3-48

56

2,1

4-40

40

2,35

5-40

40

2,65

6-32

32

2,85

8-32

32

3,5

10-24

24

3,9

12-24

24

4,5

1/4"-20

20

5,1

5/16"-18

18

6,6

3/8"-16

16

8,0

7/16"-14

14

9,4

1/2"-13

13

10,8

9/16"-12

12

12,2

5/8"-11

11

13,5

3/4"-10

10

16,5

7/8"-9

9

19,5

1"-8

8

22,25

Unified Fine (UNF)

Thread Fine Pitch Max Core Dia(mm)
Drill for tap

(mm)

0-80

80

1,25

1-72

72

1,55

2-64

64

1,9

3-56

56

2,15

4-48

48

2,4

5-44

44

2,7

6-40

40

2,95

8-36

36

3,5

10-32

32

4,1

12-28

28

4,7

1/4"-28

28

5,5

5/16"-24

24

6,9

3/8"-24

24

8,5

7/16"-20

20

9,9

1/2"-20

20

11,5

9/16"-18

18

12,9

5/8"-18

18

14,5

3/4"-16

16

17,5

7/8"-14

14

20,4

1"-14

14

23,25

More tables coming later.

Enjoy!

www.daaseberga.se