Stub Acme (29-degree) Thread Depth and Dimensions

Stub Acme (Machinery's Handbook / ASME B1.8) keeps the 29-degree flank but cuts the thread height to h = 0.3 P instead of P/2: pitch P = 1/TPI, thread depth h = 0.3 P, pitch diameter = D - 0.3 P, external minor (root) = D - 0.6 P, crest flat = P/2 - 0.3P tan(14.5 deg) = 0.4224 P. A 1-5 Stub Acme (1 in, 5 TPI): 0.200 in pitch, 0.060 in depth, 0.940 in pitch dia, 0.880 in minor, 0.0845 in crest flat. The shallow thread leaves a stronger root and needs less axial space, used on hardened or heavily loaded lead screws, valve stems, and thin-wall parts where a full-depth Acme would over-weaken the section. Cut with a 29-deg tool and verify over wires. ASME B1.8 and a thread gauge govern.

pitch = 1/TPI; thread depth h = 0.3 P; pitch dia = D - 0.3 P; external minor = D - 2h = D - 0.6 P; crest flat = P/2 - h tan(14.5 deg) = 0.4224 P; 29-degree included angle.

Stub Acme (29-degree) thread dimensions (Machinery's Handbook / ASME B1.8), by name.

The Stub Acme geometry (0.3 P depth, 0.4224 P crest flat, D - 0.3 P pitch diameter) is standard published machining reference (Machinery's Handbook); the major diameter and TPI are the thread's spec.

Estimate. AHJ and licensed professional govern.

Field names used by the API: major_dia_in, tpi, pitch_in, thread_depth_in, pitch_dia_in, minor_dia_in, crest_flat_in

• Stub Acme depth external thread depth h = 0.3 P (vs P/2 for general Acme)Machinery's Handbook / ASME B1.8
• Diameters pitch dia = D - 0.3 P; external minor = D - 0.6 PStub Acme thread geometry
• Crest flat and angle crest flat = P/2 - 0.3P tan(14.5 deg) = 0.4224 P; included angle 29 degreesASME B1.8