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BSPT & BSPP Thread

What is BSPT & BSPP Thread?

BSP: Represents British standard thread, also known as Wyeth profile angle 55 °

BSPT stands for British standard taper pipe thread profile according to AS 1722.1, BS 21, ISO 7

BSPP: Represents British standard straight pipe thread profile according to AS 1722.2, ISO 228

BSPT external thread and BSPT non-adjustable internal thread seal.

The threaded surfaces are in contact with each other.

It is recommended to use thread sealant to connect the external BSPT thread with the internal BSPT thread. Measure the outer diameter of the BSPT external thread and the inner diameter of the internal thread near the first complete tooth at the end of the joint.

BSPT external thread and BSPP external thread with 30 ° cone (60 ° included angle) are matched with BSPP internal thread rotary joint with 30 ° cone and BSPP external thread rotary joint with O-ring.

BSPT & BSPP Thread

BSPP O-ring seal male thread connector has a straight thread and O-ring with metal positioning ring. It is sealed with the outer plane of the BSPP internally threaded port. The BSPP external thread (with the chamfer for sealing the fixed gasket) is also sealed with the external plane of the BSPP internal thread port.

The regular surface needs to be machined with a screw hole plane to ensure an effective seal. Elbows and tees are equipped with lock nuts to position the joint in the desired direction.

For BSPP external thread and BSPP internal thread flat rotary joints, a suitable soft washer should be added between the end face and the seal. It is suitable for low pressure.

BSPT & BSPP Thread Size

Dimensions & PitchMarking SizeBSPT Outer DiameterBSPP Outer DiameterBSPT Internal DiameterBSPP Internal Diameter
Inch -TPI mm/ Inchmm/ Inchmm/ Inchmm/ Inch
1/8– 28-029,5/0.37  9,6/0.388,4/0.33  8,6/0.34
3/8– 19-0616,3/0.6416,5/0.6514,7/0.5915,2/0.60
1/2– 14-0820,4/0.8020,8/0.8218,3/0.7219,1/0.75
5/8– 14-1022,5/0.8922,8/0.9020,6/0.8120,8/0.82
3/4– 141225,9 1.0226,3 1.0423,9 0.9424,6 0.97
1– 11-1632,6 1.2833,1 1.3029,7 1.1730,7 1.21
1.1/4 – 112041,1/1.6241,8/1.6438,6/1.5239,4/1.55
1.1/2 – 11-2447,0/1.8547,7/1.8844,5/1.7545,5/1.79
2 -11-3258,6/2.3159,5/2.3456,4/2.2257,4/2.26
2.1/2 – 11-4074,1/2.9275,1/2.9571,9/2.8372,6/2.86  
3 – 11-4886,6/3.4187,9/3.4684,6/3.3385,4/3.36  

The thread size refers to the nominal bore of the pipe.

Subtract about 1/4 ’’ (6mm) of the measured diameter of the thread to obtain the nominal pipe diameter.

Pitch refers to the number of threads per inch (TPI).

“Gas (airtight thread)”, “R” & “G” also refer to BSP. “Externally threaded cast iron (pipe)” may be BSP or NPT.

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