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Thread Identification

Quick Search: Please Enter Measurement Taken with Calipers

 Click to view Dash Size Thread Guide printable table

THREAD IDENTIFICATION GUIDE

How to use the chart

Outside Dia. Male
(mm)
Outside Dia. Male
(inches)
Inside Dia Female
(mm)
Inside Dia. Female
(Inches)

Pitch/Inch

TPI

Forms Metric DIN/ Metric ISO 6149 BSPP/BSPT NPTF

ORB/JIC/ORFS (UNF)

3.8 - 3.9 0.150 - 0.154 3.2 - 3.4 0.126 - 0.134 0.7
M 4      
4.0 - 4.2 0.158 - 0.165 3.4 - 3.6 0.134 - 0.142 36
      No. 8
4.6 - 4.8 0.181 - 0.189 4.0 - 4.2 0.157 - 0.165 32
      No. 10
4.8 - 4.9 0.189 - 0.193 4.1 - 4.3 0.161 - 0.169 0.8
M 5      
5.7 - 5.9 0.224 - 0.232 4.9 - 5.2 0.193 - 0.205 1 B M 6      
7.7 - 7.9 0.303 - 0.311 6.9 - 7.2 0.272 - 0.283 1 B, C, E, F M 8x1      
7.7 - 7.9 0.303 - 0.311 6.6 - 6.9 0.260 - 0.272 1.25 B M 8       
7.7 - 7.9 0.303 - 0.311 6.8 - 7.1 0.268 - 0.280 24 E, F ,G       5/16x24
7.0 - 7.9 0.275 - 0.311 6 - 6.9 0.236 - 0.271 27 D     1/16  
8.0 - 8.2 0.315 - 0.323 7.0 - 7.2 0.276 - 0.283 18 E, F, G       5/16x18
9.5 - 9.7 0.374 - 0.397 8.5 - 8.8 0.335 - 0.346 28 B, C, D   G1/8    
9.5 - 9.7 0.374 - 0.382 8.5 - 8.7 0.335 - 0.343 24 E, F, G       3/8x24
9.7 - 9.9 0.382 - 0.390 8.9 - 9.2 0.350 - 0.362 1 A, B, C, E, F M 10x1      
9.7 - 9.9 0.382 - 0.390 8.6 - 8.9 0.339 - 0.350 1.25
M 10x1.25      
9.7 - 9.9 0.382 - 0.390 8.4 - 8.7 0.331 - 0.343 1.5
M 10      
9.4 - 10.3 0.370 - 0.406 8.3 - 9.2 0.327 - 0.362 27 D     1/8  
10.9 - 11.1 0.429 - 0.437 9.7 - 10.0 0.382 - 0.394 20 E, F, G       7/16x20
11.0 - 11.3 0.433 - 0.445 10.0 - 10.2 0.394 - 0.402 24 E, F, G       7/16x24
11.7 - 11.9 0.461 - 0.469 10.6 - 10.9 0.417 - 0.429 1.25
M 12x1.25      
11.7 - 11.9 0.461 - 0.469 10.4 - 10.7 0.409 - 0.421 1.5 B,C M 12x1.5      
11.6 - 11.9 0.457 - 0.469 10.1 - 10.4 0.398 - 0.409 1.75
M 12      
12.2 - 12.4 0.480 - 0.488 11.2 - 11.4 0.441 - 0.449 1.5
M 12.65      
12.5 -12.7 0.492 - 0.500 11.3 - 11.7 0.445 - 0.461 20 E, F, G       1/2x20
12.9 - 13.2 0.508 - 0.520 11.4 - 11.9 0.449 - 0.469 19 B, C, D   G1/4    
12.6 - 13.7 0.496 - 0.539 10.7 - 11.5 0.421 - 0.452 18 D     1/4  
13.8 – 14.0 0.543 – 0.551 12.4 – 12.6 0.488 – 0.496 1.5 B, C, E, F M 14x1.5      
14.0 – 14.2 0.552 – 0.561 12.8 – 13.1 0.502 – 0.515 18 E, F, G       9/16x18
14.1 - 14.2 0.554 - 0.561 13.1 - 13.4 0.517-0.527 24
      9/16x24
15.7 - 15.9 0.618 - 0.626 14.4 - 14.7 0.567 - 0.579 1.5 B, C, E, F M 16x1.5      
15.6 - 15.9 0.614 - 0.626 13.8 - 14.2 0.543 - 0.560 2
M 16       
15.7 - 15.9 0.618 - 0.626 14.4 - 14.7 0.567 - 0.579 16
      5/8x16
15.9 - 16.1 0.626 - 0.634 14.4 - 14.6 0.567 - 0.575 18 E, F, G       5/8x18
16.4 - 16.7 0.646 - 0.657 14.9 - 15.4 0.587 - 0.606 19 B, C, D   G3/8    
16.0 - 17.1 0.629 - 0.673 14.2 - 14.8 0.559 - 0.582 18 D     3/8  
17.2 - 17.4 0.677 - 0.685 15.7 - 15.9 0.618 - 0.626 16 E, F, G       11/16x16
17.8 - 18.0 0.701 - 0.709 16.4 - 16.6 0.646 - 0.654 1.5 B, C, E M 18x1.5      
18.8 - 19.0 0.739 - 0.748 17.3 - 17.7 0.682 - 0.696 16 E, F, G       3/4x16
18.8 - 19.1 0.740 - 0.752 17.3 - 17.8 0.681 - 0.701 18
      3/8x18
19.7 - 19.9 0.776 - 0.783 18.9 - 19.2 0.744 - 0.756 1 A M 20x1      
19.7 - 19.9 0.776 - 0.783 18.4 - 18.7 0.724 - 0.736 1.5 A M 20x1.5      
19.6 - 19.9 0.772 - 0.783 17.3 - 17.7 0.681 - 0.697 2.5 A M 20      
20.4 - 20.6 0.802 - 0.811 18.9 - 19.3 0.745 - 0.759 16 E, F, G       13/16x16
20.7 - 20.9 0.815 - 0.823 18.6 - 19.2 0.732 - 0.756 14 B, C, D   G1/2    
20.4 - 21.3 0.803 0.839 17.4 - 18.5 0.728 - 0.685 14 D     1/2  
21.7 - 21.9 0.854 - 0.862 20.4 - 20.7 0.803 - 0.815 1.5 A M 22x1.5      
21.9 - 22.6 0.862 - 0.890 20.3 - 20.8 0.799 - 0.819 14 E, F, G       7/8x14
23.7 - 23.9 0.933 - 0.941 22.4 - 22.7 0.882 - 0.894 1.5 A M 24x1.5      
23.6 - 23.9 0.929 - 0.941 20.8 - 21.3 0.819 - 0.839 3 A M 24       
25.1 - 25.4 0.989 - 1.000 23.1 - 23.6 0.909 - 0.929 12 E, F, G       1x12
25.1 - 25.4 0.989 - 1.000 23.1 - 23.6 0.909 - 0.929 14 E, F, G       1x14
25.7 - 26.0 1.012 - 1.024 24.4 - 24.6 0.961 - 0.969 1.5 A M 26x1.5      
26.2 - 26.4 1.031 - 1.039 24.1 - 24.7 0.949 - 0.972 14 B, C, D   G3/4    
26.6 - 26.9 1.047 - 1.059 24.8 - 25.2 0.976 - 0.992 2 A M 27x2      
26.8 - 27.0 1.055 - 1.063 24.7 - 24.9 0.972 - 0.980 12 E, F, G       1 1/16x12
26.8 - 27.0 1.055 - 1.063 24.7 - 24.9 0.972 - 0.980 14         1 1/16x14
25.5 - 26.7 1.00 - 1.051 22.5 - 23.6 0.886 - 0.929 14 D     3/4  
28.3 - 28.6 1.114 - 1.126 26.3 - 26.8 1.035 - 1.055 12
      1 1/8x12
29.7 - 29.9 1.169 - 1.18 28.4 - 28.7 1.118 - 1.130 1.5
M 30x1.5      
29.7 - 29.9 1.169 - 1.18 28.4 - 28.7 1.118 - 1.130 2 B, C, E, F M 30x2      
30.0 - 30.2 1.181 - 1.189 27.9 - 28.1 1.098 - 1.106 12 E, F, G       1 3/16x12
31.5 - 31.7 1.240 - 1.248 29.5 - 30.0 1.161 - 1.181 12 E, F, G       1 1/4x11 1/2
32.9 - 33.2 1.295 - 1.307 30.3 - 30.9 1.193 - 1.217 11 B, C, D   G1    
32.7 - 33.0 1.287 - 1.299 30.8 - 31.2 1.213 - 1.228 2 B, C, E, F M 33x2      
32.4 - 33.2 1.276 - 1.307  31.1 - 31.3 1.224 - 1.232 12 E, F, G       1 5/16x12
32.4 - 33.4 1.275 -1.315 28.5 - 29.6 1.122 - 1.165 11 1/2 D     1  
35.7 - 35.9 1.406 - 1.413 34.4 - 34.7 1.354 - 1.366 1.5
M 36x1.5      
35.6 - 35.9 1.402 - 1.413 33.8 - 34.2 1.331 - 1.346 2 B, C M 36x2      
36.2 - 36.5 1.425 - 1.437 34.2 - 34.4 1.346 - 1.354 12 E, F, G       1 7/16x12
37.7 - 37.9 1.484 - 1.492 36.4 - 36.7 1.433 - 1.445 1.5
M 38x1.5      
37.8 - 38.1 1.488 - 1.500 35.8 - 36.4 1.409 - 1.433 12
      1 1/2x12
41.1 - 41.3 1.618 - 1.626 39.1 - 39.3 1.539 - 1.547 12 E, F, G       1 5/8x12
41.6 - 41.9 1.638 - 1.650 38.9 - 39.6 1.531 - 1.559 11 B, C, D   G 1 1/4    
41.7 - 41.9 1.642 - 1.650 40.4 - 40.7 1.591 - 1.602 1.5
M 42x1.5      
41.6 - 41.9 1.638 - 1.650 39.8 - 40.2 1.567 - 1.583 2 B, C, E, F M 42x2      
41.3 - 42.2 1.626 - 1.661 37.0 - 38.1 1.457 - 1.500 11 1/2 D     1 1/4  
42.6 - 42.8 1.677 - 1.685 40.6 - 40.8 1.598 - 1.606 12 E, F, G       1 11/16x12
44.7 - 44.9 1.760 - 1.768 43.4 - 43.7 1.709 - 1.720 1.5
M 45x1.5      
44.7 - 44.9 1.760 - 1.768 43.4 - 43.7 1.709 - 1.720 2 B, C M 45x2      
47.4 - 47.8 1.866 - 1.882 44.8 - 45.5 1.764 - 1.791 11 B, C, D   G 1 1/2    
47.4 - 47.6 1.866 - 1.874 45.3 - 45.5 1.783 - 1.791 12 E, F, G       1 7/8x12
47.6 - 47.9 1.874 - 1.886 45.8 - 46.2 1.803 - 1.819 2 B, C, E, F M 48x2      
47.4 - 48.3 1.866 - 1.902 43.5 - 44.9 1.713 - 1.768 11 1/2 D     1 1/2  
50.5 - 50.7 1.988 - 1.996 48.5 - 48.7 1.909 - 1.917 12 E, F, G       2x12
51.8 - 52.0 2.039 - 2.047 49.8 - 50.0 1.961 - 1.969 2
M 52x2      
51.7 - 52.0 2.035 - 2.047 50.4 - 50.6 2.003 - 2.011 1.5
M 52x1.5      
59.3 - 59.6 2.335 - 2.346 56.7 - 57.3 2.232 - 2.256 11 B, C, D   G2    
59.7 - 59.9 2.350 - 2.358 58.4 - 58.7 2.299 - 2.311 1.5
M 60x1.5      
59.7 - 59.9 2.350 - 2.358 58.4 - 58.7 2.299 - 2.311 2   M 60x2      
59.5 - 60.3 2.342 - 2.374 55.0 - 56.5 2.165 - 2.224 11 1/2 E, F, G     2  
63.2 - 63.4 2.487 - 2.498 61.2 - 61.7 2.410 - 2.428 2 B, C M 60x2      
79.7 - 79.9 3.138 - 3.146 78.4 - 78.7 3.087 - 3.098 1.5
M 80x1.5      

 

Identifying Port Size

 

Step one 

· Measure the thread diameter of the Male or Female threads with calipers.

MaleandFemale

 

Male Thread

       Female Thread

Figure 1

example1

 

 

 

Figure 2
 

Step Two

· Determine the threads per inch or the pitch using a thread gauge to identify the

  thread size and look-up in the following table (Figures 3 & 4)

MEASURING THE PITCH(Metric) or (TPI)

TPI

 

Figure 3

ACCEPTABLE  FITS

No visible gaps between thread and thread gauge

AcceptableFit

Figure 4

Identifying Port Size Example – How to Measure Threads:                                 

Example2

 

 

 

 

Figure 5

 

 

Example: Step one MEASURE THE THREAD DIAMETER.  

Start by measuring the male thread with a set of calipers. The value that you read 
off of the calipers is 13.9mm (Outside Diameter, Figure 1)
 
 

Example: Step two MEASURE THE PITCH

Take your Thread Pitch Gauge and try to match up the threads as illustrated in Figure 3
Your Thread Pitch Gauge indicates that the pitch is 1.5 Metric
 
Example: Review Chart Thread Identification Guide
You should be confident now that your thread is a M14x1.5 

 

 

 

For Part Identification see Sealing Forms Article