Single-Point Thread Cutting Depth

Pitch = 1/TPI; the full-form external thread height is 0.6134 x pitch (the UN external truncation). A 1/2-13 has a 0.0769 in pitch and a 0.0472 in radial depth; a 3/4-10 is 0.0613 in deep. Because most machinists feed with the COMPOUND set to 29.5 deg (just under the 30-deg half-angle, so the tool cuts mainly on the leading flank), the compound travels farther than the radial depth: compound infeed = depth / cos(29.5), so the 1/2-13 needs 0.0542 in of compound travel. Feed in over several passes with lighter finishing cuts, and verify with a thread gauge or the three-wire method rather than the depth alone. A setup aid; the thread standard (UN/UNJ/metric), the tool geometry, and a thread gauge govern the finished part.

pitch_in = 1 / tpi; single_depth_in = 0.6134 x pitch_in (60-degree UN external thread height); compound_infeed_in = single_depth_in / cos(29.5 degrees).

Single-point 60-degree (Unified/UN) external thread cutting depth and 29.5-degree compound infeed (Machinery's Handbook threading practice), by name; the thread standard, the tool geometry, and a thread gauge govern the finished part.

The thread-depth geometry (0.6134 x pitch for a UN external thread, and the 29.5-degree compound-infeed trig) is public machining practice; the threads-per-inch is the thread's spec.

Estimate. AHJ and licensed professional govern.

Field names used by the API: tpi, single_depth_in, compound_infeed_in

• UN external thread depth pitch = 1/TPI; external thread height = 0.6134 x pitch (60-degree UN truncation, from the 0.866 P sharp-V)Machinery's Handbook (Unified thread form)
• Compound infeed compound set to 29.5 degrees; infeed = radial depth / cos(29.5) so the tool cuts on the leading flank; verify with a gauge / three-wire methodsingle-point threading practice