Thread Angle
Thread angle is the included angle between the two flanks of a thread profile measured in an axial section. Common machine threads use 60° for ISO metric and UNC/UNF forms, 55° for Whitworth/BSF, and 30° or 29° for trapezoidal power threads. The angle dictates tool geometry and CNC threading cycle parameters.
On the shop floor, thread angle is verified before any threading pass. The operator checks the print callout and matches it to the insert's nose form; a 60° ISO thread requires a 60° insert, while a 55° Whitworth form needs the corresponding profile. In Fanuc-style controls, the angle is entered into the multi-pass threading cycle so the tool approaches with the correct flank clearance and infeed strategy. If the programmed angle conflicts with the insert geometry, the flanks will not seat properly even if pitch and major diameter measure within tolerance. For thread milling, the same angle determines cutter engagement and flank generation. Lead angle and helix angle are separate values that affect chip load and tool orientation, but they must not be confused with the thread profile angle. In assemblies, matching the thread form prevents binding, stripping, and loss of clamping load.
What does thread angle control in a CNC lathe?
It controls the profile form the control expects during the threading cycle and helps determine whether the tool path and insert geometry will generate the correct flank angles for the specified thread standard.
Is thread angle the same as pitch?
No. Pitch is the axial distance between adjacent thread crests, while thread angle is the included angle between the flanks of the thread profile.
Why does a 60° thread dominate general manufacturing?
Because ISO metric and UNC/UNF systems both use 60° flank geometry, making it the most common general-purpose form for fasteners and most CNC lathe threading setups.