The hardest part here has to be hitting an angled bore eleven inches deep and holding it to size in tool steel. The maker went at it with helical interpolation at a fixed angle on a Giddings & Lewis machine, running a 1"×12" indexable cutter, and the outcome speaks for itself: no honing was needed afterwards, which the maker credits to having helicaled the bore with that cutter. For a bore in HH P-20 tool steel, skipping the honing step entirely seems like the real achievement of the whole job.
The part itself is a raised feature sitting in the middle of a core, with the angled bore put in for a horn pin. The purpose was to check the fit of a gadget pin, and the check was done by inserting a cylindrical metal component attached to a threaded rod into the bore. Coming out 0.0002 inches oversized on a 1.2502 inch bore, eleven inches deep, is tight work. That said, the two tenths over is the one open item I would want to hear more about, since it is the only number that did not land exactly on target.
The finishing sequence also stands out: cleaning, chamfering, deburring, bottom-tapping, and stone smoothing all got done. It reads as a complete workflow rather than just the cutting step.
One more thing worth noting is the programming side. The maker reports being proficient across Heidenhain, Fanuc, Allen Bradley, and Tosnuc, and says being able to helical-interpolate this bore is something they are proud of. That pride seems well earned on a job like this.