BSPP Thread data sheet

Basic Thread Dimensions

* The below values are nomoinal (without tolerances) and are valid for both external and internal threads.

Property mm Inch
Nominal Pipe Size (Ø) 2 1/2" ...
Pitch (TPI) (P) 11 ...
Pitch (Distance) (P) 2.309 0.0909
Thread V half Angle (α) 27.5° 27.5°
Height of sharp V (H) 2.218 0.0873
Thread height (h) 1.479 0.0582
Root/Crest Radius (r) 0.317 0.0125
Major Diameter (D) 75.184 2.96
Pitch Diameter (D2) 73.705 2.9018
Minor Diameter (D1) 72.227 2.8436
Tap Drill Size (Td) -999.0 -39.3307
Thread Family BSPP (G)
Relevant Standards ISO 228-1, ISO 228-2

Tolerances for all Classes


BSPP G 2 1/2 (Internal Thread)

Property Minimum Maximum
Minor Diameter (D1) 72.227 mm (2.8436 ") 72.867 mm (2.8688 ")
Pitch Diameter (D2) 73.705 mm (2.9018 ") 73.922 mm (2.9103 ")

BSPP G 2 1/2-A (External Higher precision)

Property Minimum Maximum
Major Diameter (d) 74.75 mm (2.9429 ") 75.184 mm (2.96 ")
Pitch Diameter (d2) 73.488 mm (2.8932 ") 73.705 mm (2.9018 ")

BSPP G 2 1/2-A (External Low precision

Property Minimum Maximum
Major Diameter (d) 74.75 mm (2.9429 ") 75.184 mm (2.96 ")
Pitch Diameter (d2) 73.271 mm (2.8847 ") 73.705 mm (2.9018 ")

* For More Threadibg Information go to the BSP Thread Calculator

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