Propellers have come a long way. The first experimental forms tried to emulate the Archimedes' screw and how a wood screw works. Observation said this was logical hypothesis but disappointed inventors only found awful results. They didn't factor tubing that made Archimedes' screw function. Quite some time passed before the shape and educated guesses of bird flight visualized the foil; opposing flat and concave surface. Josef Ressel is recorded first with a successful device.
Pardon what will seem to ramble;
I believe this form of milling is called 'scarfing'.
At 0:43 [among others] of the 1:09 GIF, the face mill is intentionally canted to the surface, compared to how we normally perceive milling. There isn't any flat surface on a prop, some straight lines, but no flats. Though it rotates, essentially works same as an airfoil - an aircraft's wing. Canting develops the profile, made up of these successive, equal, ~ parallel and shallow 'grooves', lacking a better term. Being multi-axis, a single cutter removes cast layer into solid material, over much of the surface using different angles, delivering intended profile[s] at the same time. Also, the inserts probably aren't cornered; looking at chips, feed rate and finish tells one they carry a decent radius, or completely round. Later will be dressed, removing about a third of the crest between.
Not long ago, a thread about fly-cutting mentioned 'flat'. In actuality that is rare, a very large radius is more common; difficult to see or measure due to part width.
I commented some machine tables use this effect intentionally to reduce friction under large parts; against near impossible feat removing every speck from a large surface like a radial drill. Those shallow grooves are usually about 1"-1.25" and the land [crest] maybe 1/16 to .090 width.
A photocopy used to circulate, diagramming long form mathematics to solve for angle and cutter diameter to produce intended depths and radius. When I say Long Form, I mean it; covered the entire sheet.
There has been a great deal of math-prowess displayed here of late. Would be very happy, if a member should write and share a program for this process. I think his username is mklotz. . .
So after writing I finished the longer video. Better than how-it's-made topic, but typical verbal hype. Like a tungsten cutter "grinding away", or "painting" the finish [varnish or lacquer surely] to keep from "rusting". AL-bronze, Si-bronze, High Copper, Beryllium? Really?
Last edited by Toolmaker51; May 6, 2019 at 06:04 PM.
...we'll learn more by wandering than searching...
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