Stub Acme (29-degree) Thread Depth and Dimensions
Stub Acme thread depth and dimensions - the shallower 29-degree form, with the thread height cut to 0.3 P.
Example
You enter
- Major (nominal) diameter (in) 1
- Threads per inch (TPI) 5
You get
- Pitch (in) 0.2
- Thread depth (in) 0.06
- Pitch dia (in) 0.94
- Minor dia (in) 0.88
- Crest flat width 0.0845 in
Checked against published worked examples from: Engineers Edge, reproducing ASME/ANSI B1.8-1988 (R2001).
Details, formula, and sources
ScopeStub 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, basic minor (the nut's minimum minor; the screw's is smaller per B1.8) = 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.
Formula or tablepitch = 1/TPI; thread depth h = 0.3 P; pitch dia = D - 0.3 P; basic minor = D - 2h = D - 0.6 P; crest flat = P/2 - h tan(14.5 deg) = 0.4224 P; 29-degree included angle.
Source and editionStub Acme (29-degree) thread dimensions (Machinery's Handbook / ASME B1.8), by name.
Free accessThe 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.
What governsEstimate. AHJ and licensed professional govern.
API field namesmajor_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; basic minor (internal thread minimum; the external thread's maximum minor is smaller per ASME B1.8) = 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