G76 Threading Infeed Calculator

Inputs

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Total radial infeed (X depth per side). External 60° threads: ≈ 0.6134 × pitch — 0.92 mm for M10 × 1.5, 0.0383 in for 16 TPI.
in
Cutting passes before spring passes. Common practice: 5-8 for fine pitches, 8-12 for coarse or tough materials.
passes
Below this the insert rubs instead of cutting (the Q/minimum-DOC setting on the control). 0.025 mm = 0.001 in is a common floor; set 0 to skip the check.
in

Results

Default result
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First pass depth(Δd₁)
0.0148in

d ÷ √N — the heaviest cut of the cycle.

Also computed

Last pass depth(Δd_N)Pass0.00316in

Above the minimum cut depth — every pass still cuts.

First : last ratio4.69

Equal-area infeed concentrates depth early; the ratio grows with pass count.

Method notes 10 notes
  • Pass 1: cut 0.376 mm → 0.376 mm total (0.0148 in → 0.0148 in)
  • Pass 2: cut 0.156 mm → 0.531 mm total (0.0061 in → 0.0209 in)
  • Pass 3: cut 0.119 mm → 0.651 mm total (0.0047 in → 0.0256 in)
  • Pass 4: cut 0.101 mm → 0.751 mm total (0.0040 in → 0.0296 in)
  • Pass 5: cut 0.089 mm → 0.840 mm total (0.0035 in → 0.0331 in)
  • Pass 6: cut 0.080 mm → 0.920 mm total (0.0032 in → 0.0362 in)
  • Each pass removes the same chip area (∝ d²/N) — that is the whole point of the √(n/N) ladder, and why the last passes are so shallow.
  • Depths are radial (X per side). Flank or modified-flank infeed (the 29-30° compound angle on 60° threads) changes the path, not these depths.
  • Add 1-2 spring passes at zero infeed after the ladder; they relieve deflection and clean the flanks.
  • Thread depth for external 60° forms ≈ 0.6134 × pitch; verify against the thread spec and measure over wires for class fits.

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