Common Thread Forms

ISO M (Metric) and UN (Unifi ed National) UNJ (controlled root radius) Whitworth (BSW)

Use: Fittings and pipe couplings for gas, water, and

Use: All branches of mechanical industry.Use: Aircraft and space industry.sewer lines (replaced by ISO).
American Buttress NPT (American National Pipe Thread) BSPT (British Standard Pipe Thread)

1/2 D play

1/2 D2 play axis of screw taper 1:16 taper 1:16

1/2 D1 play axis of screw

Use: Fittings and pipe couplings. Use: Fittings and pipe couplings. Use: Pipe thread for steam, gas, and water lines.

TR DIN 103 Acme Acme, truncated (Stub)

nut 1/2 D play 1/2 D play

1/2 D1 play 1/2 D2 play

screw1/2 D1 play1/2 D2 play
A = 0,0307 P
B = 0,3707 P—x D playA = 0,4224 P
C = 0,3707 P—(D1 play—D2 play)B = 0,4224 P—x D play

Use: Mechanical industry for motion Use: Acme-General is used in mechanical industry for C = 0,4224 P—(D1 play—D2 play)

transmission screws. motion transmission screws. Use: Where normal Acme is too deep.

API Casing and Tubing Round Thread Form

pitch line

taper = 62,5mm per metre on diameter

NOTE: Taper shown exaggerated.