Thread Identification

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THREAD IDENTIFICATION GUIDE

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