BSPP Vs BSPT

BSPP vs BSPT are common pipe thread types in the mold industry. Correct selection of BSPP or BSPT is critical to the leak tightness and performance of mold cooling systems, pneumatic components, and hydraulic fittings.

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BSPP Thread (G Thread)

G = BSPP = BSPF = BSPM = PS

The letter “G” stands for “Gas” (some say it comes from the German word “Gewinde,” meaning “thread”), as it was initially used in gas pipelines. We refer to G as pipe thread because the first letter of “Guan” (pipe in Chinese) is the same as G.

G threads come in internal and external types and are used for non-sealing connections. The current standard is BS EN ISO 228-1, while the old standard BS 2779 is now obsolete.

Markers	Size	Category	Major Diameter	Pitch	Threads Per Inch	Pitch Diameter	External Thread	Thread Height	Minor Diameter
			mm	mm	TPI	mm	Minor Diameter	mm	mm
			d=D	p		d2=D2	d3	H1
G1/8	1/8″	BSPP	9.728	0.907	28	9.147	8.566	0.581	8.7
G1/4	1/4″	BSPP	13.157	1.337	19	12.301	11.445	0.856	11.6
G3/8	3/8″	BSPP	16.662	1.337	19	15.806	14.95	0.856	15
G1/2	1/2″	BSPP	20.955	1.814	14	19.793	18.631	1.162	19
G5/8	5/8″	BSPP	22.911	1.814	14	21.749	20.587	1.162	20.75
G3/4	3/4″	BSPP	26.441	1.814	14	25.279	24.117	1.162	24.5
G7/8	7/8″	BSPP	30.201	1.814	14	29.039	27.877	1.162	28
G1	1″	BSPP	33.249	2.309	11	31.77	30.291	1.479	30.5
G1-1/8	1-1/8″	BSPP	37.897	2.309	11	36.418	34.939	1.479	35
G1-1/4	1-1/4″	BSPP	41.91	2.309	11	40.431	38.952	1.479	39.5
G1-3/8	1-3/8″	BSPP	44.323	2.309	11	42.844	41.365	1.479	41.5
G1-1/2	1-1/2″	BSPP	47.803	2.309	11	46.324	44.845	1.479	45
G1-3/4	1-3/4″	BSPP	53.746	2.309	11	52.267	50.788	1.479	51
G2	2″	BSPP	59.614	2.309	11	58.135	56.656	1.479	57
G2-1/4	2-1/4″	BSPP	65.71	2.309	11	64.231	62.752	1.479	63
G2-1/2	2-1/2″	BSPP	75.184	2.309	11	73.705	72.226	1.479	72.5
G2-3/4	2-3/4″	BSPP	81.534	2.309	11	80.055	78.576	1.479	79
3	3″	BSPP	87.884	2.309	11	86.405	84.926	1.479	85.5
G3-1/4	3-1/4″	BSPP	93.98	2.309	11	92.501	91.022	1.479	91
G3-1/2	3-1/2″	BSPP	100.33	2.309	11	98.351	97.372	1.479	97.75
G3-3/4	3-3/4″	BSPP	106.68	2.309	11	105.201	103.722	1.479	104
G4	4″	BSPP	113.03	2.309	11	111.55	110.072	1.479	110.5
G4-1/2	4-1/2″	BSPP	125.73	2.309	11	124.251	122.772	1.479	123
G5	5″	BSPP	138.43	2.309	11	136.951	135.472	1.479	136
G5-1/2	5-1/2″	BSPP	151.13	2.309	11	149.651	148.172	1.479	148.5
G6	6″	BSPP	163.83	2.309	11	162.351	160.872	1.479	161.5

BSPT Thread (R thread)

R=BSPT=PT

BSPT – British Standard Pipe Taper, also known as PT thread, is used only for general sealing connections. The old standard for BSPT was BS 21, but in the new standard BS EN 10226-1, R threads have replaced it.

Size	Threads Per Inch	Pitch	Thread Height	Reference Diameter	Pitch Diameter	Minor Diameter	Reference Distance	Limit Deviation	Effective Thread Length	Assembly Allowance	Limit Deviation of Internal Thread Diameter
	TPI	mm	mm	mm	mm	mm	mm	mm	mm	mm	mm

1/16	28	0,907	0,581	7,723	7,142	6,561	4	+ /- 0,9	6,5	2,5	+ /-0,071
1/8	28	0,907	0,581	9,728	9,147	8,566	4	+ /- 0,9	6,5	2,5	+ /-0,071
1/4	19	1,337	0,856	13,157	12,301	11,445	6	+ /- 1,3	9,7	3,7	+ /-0,104
3/8	19	1,337	0,856	16,662	15,806	14,95	6,4	+ /- 1,3	10,1	3,7	+ /-0,104
1/2	14	1,814	1,162	20,955	19,793	18,631	8,2	+ /- 1,8	13,2	5,0	+ /-0,104
3/4	14	1,814	1,162	26,411	25,279	24,117	9,5	+ /- 1,8	14,5	5,0	+ /-0,104
1	11	2,309	1,479	33,249	31,77	30,291	10,4	+ /- 2,3	16,8	6,4	+ /-0,180
1 1/4	11	2,309	1,479	41,91	40,431	38,952	12,7	+ /- 2,3	19,1	6,4	+ /-0,180
1 1/2	11	2,309	1,479	47,803	46,324	44,845	12,7	+ /- 2,3	19,1	6,4	+ /-0,180
2	11	2,309	1,479	59,614	58,135	56,656	15,9	+ /- 2,3	23,4	7,5	+ /-0,180
2 1/2	11	2,309	1,479	75,184	73,705	72,226	17,5	+ /- 3,5	26,7	9,2	+ /-0,216
3	11	2,309	1,479	87,884	86,405	84,926	20,6	+ /- 3,5	29,8	9,2	+ /-0,216
4	11	2,309	1,479	113,03	111,551	110,072	25,4	+ /- 3,5	35,8	10,4	+ /-0,216
5	11	2,309	1,479	138,43	136,951	135,472	28,6	+ /- 3,5	40,1	11,5	+ /-0,216
6	11	2,309	1,479	163,83	162,351	160,872	28,6	+ /- 3,5	40,1	11,5	+ /-0,216

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