cutter 13 with involute cutting edges fig2 is a cross section of cutter 13 with crown convex cutting edges and fig2 is a cross section of cutter 13 with crown concave cutting edges for specific design profile of cutting edges can be different even more complicated for generating enveloping worm that will be a pinion it could be a cutter with straight cutting edges for generating an enveloping worm that will be used us a hob to generate matting gear profile of cutting edges could be crown profile with concave cutting edge for machining of enveloping worm thread surface axis of rotation of helical cutter 13 is placed in the center of base circle 8 and cutter 39 s 13 cutting edges will be located around a base circle to produce enveloping worm enveloping worm blank 6 rotates around axis w of enveloping worm blank 6 and enveloping worm blank 6 has relative motion around tooling axis z to helical cutter 13 helical cutter 13 furthermore has linear motion along its axis of rotation which is linear motion normal to cutting plane x y this linear motion is tangential feeding helical 39 s cutter 13 and enveloping worm 39 s blank 6 relative motion around tooling axis z can be done by helical cutter 13 rotating around tooling axis z with simultaneous rotation of enveloping worm blank 6 around axis z or by only rotating enveloping blank 6 around axis z speed of relative motion is a function between number of.