Knurl Blank Diameter Calculator

Inputs

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TPI: teeth per inch along the circumference (p = 1/TPI). DP: 64/96/128/160 series (p = π/DP). Linear pitch: the tooth-to-tooth distance itself, in mm.
TPI
The diameter you intended to turn before knurling — the calculator moves it to the nearest tracking size.
in
Diametral rise of form (displacement) knurling above the blank — material- and knurl-dependent; the knurl supplier’s data governs. Use 0 for cut knurling.
in

Results

Default result
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Tracking blank diameter(D′)
0.746in
Caution

Planned size gives 75.40 teeth — a partial tooth that double-cuts. Turn to the corrected diameter (-0.101 mm) for clean tracking.

Turn the blank to this — the nearest diameter holding a whole tooth count.

Also computed

Teeth around work(N)75

Correction from planned(ΔD)−0.00396in

Signed: negative = turn under your planned size.

Expected finished OD(D_f)0.7657in

Corrected blank plus your growth allowance; measure the first part and adjust.

Method notes 4 notes
  • Tracking is the whole game in form knurling: a non-integer tooth count re-enters off-pitch every revolution and chews the pattern.
  • Diametral-pitch knurls (64/96/128/160) are designed so standard fractional-inch diameters land on whole teeth — that is why they exist; TPI and metric-pitch knurls need this correction.
  • Growth is empirical: it rises with displaced volume and varies by material and tooth form — the knurl maker’s data sheet governs, and the first part calibrates it.
  • Geometry-only screen: feed, passes, speeds and lubrication come from the knurl supplier; scissor/cut knurling follows its own tool data.

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