Single-point threading calculator
An M10 × 1.5 external thread takes 6 passes to a radial infeed of 0.95 mm by Sandvik’s table (0.20, 0.19, 0.18, 0.16, 0.14 and 0.08 mm), against a basic profile depth of 0.92 mm: the makers turn a little deeper than the standard’s profile, and the last pass is the lightest. Type or pick the thread below, choose external or internal, and open the Make tab’s Passes drawing: pick a schedule to get every pass’s infeed, the compound slide travel and Z shift at your infeed angle, and the G76 cycle’s words.
Each pass takes a thinner layer than the last: the groove widens as the tool goes in, so a lighter infeed keeps the chip’s area from growing. Feeding at 29° from the radial, just under the 30° flank, the leading edge does nearly all the cutting.
How many passes does a thread take, and how deep is each?
Tool makers print a total radial infeed and a pass count for each pitch, for external and internal threads. The passes get lighter as the tool goes deeper, because the groove widens: an equal depth per pass would load the last pass far more than the first. Sandvik’s formula spreads a total over a pass count the same way, and a FANUC G76 cycle cuts the nth pass to a depth of ∆d·√n from the first cut ∆d.
On a manual lathe the compound slide is set to the infeed angle, so it travels further than the radial depth: the depth divided by the cosine of the angle. A CNC threading cycle moves each pass’s start point along Z by the depth times the tangent of the angle instead. Either way the final depth is set by the thread gauge, not by the number: the makers’ totals are starting values for their own inserts.