Knurling blank diameter calculator

A knurl tracks cleanly when the work’s circumference holds a whole number of knurl teeth. Enter the diameter you want and the knurl pitch to get the nearest good blank sizes.

Safety: knurling puts high loads on the cross-slide and work. Support long work with the tailstock, run at low speed, use plenty of oil and keep rags and fingers clear of the wheels.

How it works, guides and notes

How it works

For a straight knurl the number of teeth round the work is π × D ÷ pitch. If that isn’t close to a whole number, the wheel lands half a tooth out on the second revolution and you get a double-tracked, ragged pattern. Turning the blank to a diameter that gives a whole number of teeth fixes it. For 30° diagonal knurls the pitch round the circumference is the normal pitch ÷ cos 30°.

A form knurl pushes metal up as well as in, so the finished diameter grows. Try a test piece in the same material, and turn the blank slightly under the size you need if the finished size matters.

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