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mm thread vs inch thread

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mm thread vs inch thread

Metric Thread bolt versus inches Thread Bolt

Metric Thread bolt                       

Thread angle -  60 degree.              
Pitch-  Standard, fine ,extra fine                             
                                                              
Example  12 mm  hex bolt
Standard pitch is  1.75mm
Fine pitch is  -1.5 mm. 
Extra fine pitch is - 1.25 Mm 
 
Thread depth
Distance from crest to root .
 
Metric thread  are different fundamentally because the thread pitch (distance between each thread which is in mm) is specified instead of threads per inch or per mm.

Inches thread bolt 

Thread angle -  55 degree
 Pitch is measured in  TPI -Thread per inch
                                                     
It means how many threads are there in an inch eg 1/2 inches is 13 TPI .
So 1 inches is 25.4 so 13 TPI is 25.4/13=1.95 mm
 
service
Weight Table

Metric - Coarse and Fine Thread Pitch Chart

Diameter

Coarse Pitch

Fine Thread Pitches

 

Diameter

Coarse Pitch

Fine Thread Pitches

M1

0.25

0.2

 

 

M16

2

1.5

1

 

M1.2

0.25

0.2

 

 

M18

2.5

2

1.5

1

M1.4

0.3

0.2

 

 

M20

2.5

2

1.5

1

M1.6

0.35

0.2

 

 

M22

2.5

2

1.5

1

M1.7

0.35

 

 

 

M24

3

2

1.5

1

M1.8

0.35

0.2

 

 

M27

3

2

1.5

1

M2

0.4

0.25

 

 

M30

3.5

3

2

1.5

M2.2

0.45

0.25

 

 

M33

3.5

3

2

1.5

M2.3

0.4

 

 

 

M36

4

3

2

1.5

M2.5

0.45

0.35

 

 

M39

4

3

2

1.5

M2.6

0.45

 

 

 

M42

4.5

4

3

2

M3

0.5

0.35

 

 

M45

4.5

4

3

2

M3.5

0.6

0.35

 

 

M48

5

4

3

2

M4

0.7

0.5

 

 

M52

5

4

3

2

M5

0.8

0.5

 

 

M56

5.5

4

3

2

M6

1

0.75

 

 

M60

5.5

4

3

2

M7

1

0.75

 

 

M64

6

4

3

2

M8

1.25

1

0.75

 

M68

6

4

3

2

M9

1.25

1

0.75

 

M72

 
Specification Table
service

UNC threads according ANSI B1.1:

Major Diameter

 

Threads per inch

Major Dia.

Major Dia.

Tap Drill Size

 

Pitch

(in)

(in)

(mm)

(mm)

(mm)

#1 - 64

64

0.073

1.854

1.5

0.397

#2 - 56

56

0.086

2.184

1.8

0.453

#3 - 48

48

0.099

2.515

2.1

0.529

#4 - 40

40

0.112

2.845

2.35

0.635

#5 - 40

40

0.125

3.175

2.65

0.635

#6 - 32

32

0.138

3.505

2.85

0.794

#8 - 32

32

0.164

4.166

3.5

0.794

#10 - 24

24

0.19

4.826

4

1.058

#12 - 24

24

0.216

5.486

4.65

1.058

1/4" - 20

20

0.25

6.35

5.35

1.27

5/16" - 18

18

0.313

7.938

6.8

1.411

3/8" - 16

16

0.375

9.525

8.25

1.587

7/16" - 14

14

0.438

11.112

9.65

1.814

1/2" - 13

13

0.5

12.7

11.15

1.954

9/16" - 12

12

0.563

14.288

12.6

2.117

5/8" - 11

11

0.625

15.875

14.05

2.309

3/4" - 10

10

0.75

19.05

17

2.54

7/8" - 9

9

0.875

22.225

20

2.822

1" - 8

8

1

25.4

22.85

3.175

1 1/8" - 7

7

1.125

28.575

25.65

3.628

1 1/4" - 7

7

1.25

31.75

28.85

3.628

1 3/8" - 6

6

1.375

43.925

31.55

4.233

1 1/2" - 6

6

1.5

38.1

34.7

4.233

1 3/4" - 5

5

1.75

44.45

40.4

5.08

2" - 4 1/2

4 1/2

2

50.8

46.3

5.644

2 1/4" - 4 1/2

4 1/2

2.25