GENERAL KNURLING INFORMATION

        Knurling is widely used in industry for many applications.  Some of these include:  decorative and "grip" surfaces, repair of undersized shafts and oversize bores, and driving serrations and splines. The word "knurling" applies to both the method of production, and the rolled section on the part. It is usually produced by forcing a knurling die into the surface of a rotating part, displacing material from the original diameter. Two methods of specifying the comparative tooth spacing are currently in use - CIRCULAR PITCH and DIAMETRAL PITCH. The CIRCULAR PITCH system has been used for many years and is based on the distance between teeth (pitch) and expressed as TEETH per INCH of circumference or TPI. The DIAMETRAL PITCH system is fully explained in American Standard ANSI/ASME B94.6-1984. Unlike gearing, only four standard pitches are used (64, 96, 128, & 160) for blank diameters from 3/32" to 1". Diametral Pitch dies are designed to permit accurate tracking on standard fractional sized blanks, making blank diameter selection easier. Due to the many variables involved in any knurling operation (speeds, feeds, coolant, hardness of piece, condition of pins, etc.), determining proper blank diameters for circular pitch dies is a bit more difficult, and usually involves some amount of experimentation. The tips along with the formulas on the following pages should help, but if problems persist, feel free to call us and we'll be glad to offer our advise.

SPEEDS AND FEEDS

        Knurling is normally done at the same speed as High-Speed cutting operations.  Bump knurling from the cross-slide should be done in 10 to 20 revolutions.  (Over rolling will cause flaking and poor knurl life).  Knurls from the turret should be fed onto the work at about  .005 to  .020 per rev. (slower for harder materials faster for soft materials) and off the work about twice as fast.   

        For turret knurling, a faster, feed rate may correct a tracking problem, as this  would make a larger impression on the first revolution, thus increasing the chance of the teeth falling in place on the second revolution even though the spacing  were off slightly.

Note:  bevels or convex are recommended when traverse knurling.
Bevels  will be provided at no extra charge when requested, but beveled knurls may not be returned if ordered in error.

TRACKING (AND MIS-TRACKING)

When a single knurl makes its first revolution and then falls back into the first tooth that it rolled, it is tracking correctly.  If the circumference of the part being rolled is not an approximate multiple of the pitch of the knurl, the knurl may land somewhere between the two initial teeth, causing it to start a
new row.  This may cause double tracking (or any multiple of the initial pitch).  This problem can usually be corrected by changing the diameter of the work by +/-  .005" to .010".   Otherwise, order a special knurl.