Workshop
Put two standards side by side — 1/4 BSW vs 1/4-20 UNC, or Tr20×4 vs 3/4-6 Acme.
Thread A
Thread B
55° vs 60° — do not mix taps, dies or gauges.
Angle / form
55° Whitworth 55° radiused
Angle / form
60° 60° V
Pitch
1.270 mm
Pitch
1.270 mm
TPI
20.00
TPI
20.00
Tap / core drill
5.10 mm0.2008"Tap / core drill
5.10 mm0.2008"Major Ø
6.35 mm0.2500"Major Ø
6.35 mm0.2500"Pitch Ø
5.54 mm0.2180"Pitch Ø
5.53 mm0.2175"Minor int.
4.72 mm0.1860"Minor int.
4.98 mm0.1959"Minor ext.
4.72 mm0.1860"Minor ext.
4.79 mm0.1887"Height h
0.81 mm0.0320"Height h
0.83 mm0.0325"Compound
27.5°
Compound
29.5°