Being that I was trying to get the nuts to be as narrow to the lower legs as possible, for the minimalistic look, I needed the tapped hole to be flat bottomed. After machining of the top 'divot' and the fully threaded hole, I only have .065" of material between the two features. I peck drilled the 3/8" drill to just short of the .700" full thread depth I needed. I then used a 3/8", 4 flute, carbide end mill to open up the 37/64" dia c'bore that I need to run a 5/8-18 flat bottom tap in there. The nuts got threaded, chased again with the tap to ensure good threads, and then deburred waiting for the axle to be lathed.
Top view to show a better view of the 3-d machining that we did. They look sweet, like something off an F-1 car. Stainless sucks to machine and it\s really good at cutting your hands when trying to deal with the edge burrs and the chips, but it looks awesome machined with good carbide cutters. I know that many of your thinking, well that looks like a normal nut, why did you spend the time and money for material to make it, rather than buy it. Becuase you can't buy this nut anywhere. Most flange head nuts, are through threaded, not blind this design. Most nuts have a smaller aspect ratio of the ID thread, to hex size to OD than this. My design is the perfect fit for my bike, and that is all that I want in the end. I don't care if it takes a long time to design or make. I won't cut corners on my projects.
Axle Nuts in process. Started with that 1.625" dia 303L stainless stick. Programmed the 3-D milling with the help of Chad (BAKER Design Engineer) and Kris (BAKER Prototype Machinist) using Featurecam. Cut some slugs off of the stick, Kris milled some round pockets in the soft jaws of the small haas, and we knocked out the hex nuts to the state you see here. Note how the nut in the vise has a much smaller flange thickness on the bottom. I have already used a 2.5 dia indexable cutter to face it to the final .800" height. The other nut is next for a haircut.
