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Stock Diameters for Even Knurls

Knurls have a definite pitch, and they work best when the stock circumference is an approximate multiple of that pitch. Here is a calculator and an easy formula to find the next smaller diameter from the diameter of your work piece. The most material you ever have to remove is 0.023" for a 14-pitch knurl.

Calculator

Original Diameter Knurl Pitch Knurling Diameter
 

Calculation

Step Action Example
1 Multiply the current diameter (in inches) by the pitch factor shown below. 0.75" × 103.67 = 77.7525
2 Drop the decimals. 77
3 Divide by the pitch factor shown below. 77 ÷ 103.67 = 0.7427
4 Turn the blank down to the diameter found 0.743"

Pitch Factors

The pitch factor is simply the pitch multiplied by pi.

33 LPI Knurls

103.67

21 LPI Knurls

65.97

14 LPI Knurls

43.98

Spreadsheet

If you have Excel, here is a little spreadsheet that will calculate it all for you:

The formula in cell C4 is =ROUND(INT(A4*B4*PI())/B4/PI(),3)