G-Code Lathe Project - The Seal Cap Part 2

Part Two - Roughing the Seal Cap with G71

With the header done, this lesson removes the bulk of the material. The external profile steps down from the Ø50 flange through a Ø34 body, a Ø30 section that will later carry three serration grooves, a Ø26 relief and finally the Ø20 thread section, with a 1x45 chamfer breaking the flange shoulder. One continuous turning profile handles all of it.

Hand writing that shape would mean dozens of passes at each step. Instead we draw the finish profile once, as a subroutine, and let the G71 roughing cycle do the multiplying. This is the Type I single line version of the cycle: the profile must step down monotonically with no grooves in it, which suits this shape perfectly because we will machine the serrations elsewhere. The cycle line points at the start block, sets its own depth of cut and leaves a finish allowance on both diameter and face while the control works out every pass.

Tool nose radius compensation gets switched on with the very first feed move, so the cycle accounts for the insert radius across every corner and taper, and it is cancelled again on the retract. The subroutine gets written once and reused at the end of the series by the finishing cycle, which is exactly why the profile is worth doing properly the first time.

Download the full G-Code handout for this lesson, along with the complete Seal Cap program, here

This free lesson series follows the Seal Cap build from first sketch to finished part and is a taster of what you will learn in the 4-Course G-Code Bundle.