Attributes . ? Circular Pitch Knurls 30? Spiral Knurls 
 ? GK Series Circular Pitch Knurls
 ? The circular Pitch Knurl System is the older system and has been in use many years. The spacing of the teeth is measured by the number of teeth per inch (TPI) around the circumference. Knurling can be done with many types of holders made for knurling or with any holder (or machine) made for thread rolling. . Names