Acme (29-degree) Thread Depth and Dimensions

ScopeGeneral-purpose Acme (Machinery's Handbook / ASME B1.5): pitch P = 1/TPI, external thread depth h = P/2 + 0.010 in (0.005 finer than 10 TPI), pitch diameter = D - P/2, external minor (root) = D - P - 0.020 (0.010 finer than 10 TPI), crest flat = 0.3707 P, included angle 29 deg. A 1-5 Acme (1 in, 5 TPI): 0.200 in pitch, 0.110 in depth, 0.900 in pitch dia, 0.780 in minor, 0.0741 in crest flat. Acme carries axial load with less friction and wedging than a V-thread -- vises, presses, machine lead screws. Cut with a 29-deg tool and verify over wires. General-purpose class; Stub Acme and centralizing classes differ; ASME B1.5 and a thread gauge govern.

Formula or tablepitch = 1/TPI; thread depth h = P/2 + 0.010 in (0.005 finer than 10 TPI); pitch dia = D - P/2; external minor = D - 2h = D - P - 0.020 (0.010 finer than 10 TPI); crest flat = 0.3707 P; 29-degree included angle.

Source and editionGeneral-purpose Acme (29-degree) thread dimensions (Machinery's Handbook / ASME B1.5), by name.

Free accessThe general-purpose Acme geometry (P/2 + 0.010 depth, 0.005 finer than 10 TPI, 0.3707 P crest flat, D - P/2 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

• Acme depth external thread depth h = P/2 + 0.010 in (general-purpose clearance; 0.005 in finer than 10 TPI)Machinery's Handbook / ASME B1.5
• Diameters pitch dia = D - P/2; external minor = D - P - 0.020 (D - P - 0.010 finer than 10 TPI)Acme thread geometry
• Crest flat and angle crest flat = 0.3707 P; included angle 29 degrees; general-purpose class onlyASME B1.5