The toughest bit here looks like the deep helical boring, and that is where things got hairy. The maker ran a large endmill into a small deep hole with no thru spindle coolant, and chips packed into the center of the flutes. They suspect their own programming caused the packing rather than blaming the tool, which seems like a fair self-assessment and an honest open question since the hole diameter was never stated.
As for how the whole thing came together, most of the machining happened with the part held in an L plate on the fourth axis. The maker cut several sets of soft jaws for work holding, and shrink fit holders from Maritool and Haas were needed to reach features without collisions. The bobstay attachment section, with its angled slot and undercut, came off successfully on the fourth axis, with the slot machined at both 90 degrees and 45 degrees.
The details that stand out to me: the material is CP grade 2 titanium, chosen because grade 5 would do nothing extra for this part, and titanium makes sense for marine parts given its corrosion resistance and strength. The part is roughly 170mm long and 3.740 inches across at its widest, and it mounts at the end of a carbon tube bowsprit on a racing sailboat, where it carries the sails. A 300 degree lollipop cutter ran steep and shallow undercutting toolpaths programmed in Fusion with the manufacturing extension, which the maker has used since 2019. Tooling included a Haas 15mm modular drill that worked well despite the missing thru spindle coolant, and a half-inch five flute Helical T plus with a .06 cutter radius, 5/8 inch flute length and 3.375 inch reduced neck reach. That endmill cost 346 dollars, so the maker used it sparingly.
The outcome was mostly successful with acceptable surface finish. The maker runs a one person shop and wished for a mentor along the way, which I can understand given how much of this was figured out alone.