DISCLAIMER: this is not for the faint of heart. This first pass came out ugly.
That's a chunk of O-1 in its annealed state mounted in a vise at an angle at about 25 degrees. 1/4" 4 flute end mill at about 1200 RPM, 4 ipm. Other than a goof up in the CNC program itself (I haven't investigated but I swear Fusion 360 goofed up something in the middle) which you'll see later, it went ok.
Cleaning the serrations up with a round file. By the way, if you need to do small amounts of serrations this is how they're done, just a round file and some patience. I mainly had to bring the file to bear because of the goofup which resulted in the middle serrations way deeper than they should be.
Here it is all done with heat treatment. You can see the middle portion is pretty janky.
"Finished", lol. I didn't bother with much finish work, just cleaned it up with a 120 grit belt, filed the serrations again, and then sharpened on a sharp maker.
Observations:
1. Evil D is always poo-pooing really pointy serrations. This is a good case study on what not to do. It's hard to get the work started.
2. The lack of the small serrations makes it hard to get a good grip on the work. IMO the alternating large/small serrations are what make SpyderEdge what it is. I'm curious how Sal arrived at that design.
3. These serrations are way too deep. It's like having a stick with a bunch of needles sticking out of it. More dangerous to handle than I'm used to.
4. Could you make serrations like this in production? Ooof, well I think so. Even the serrations that roughly came out as they should needed a bit of touching up with the file to get the teeth to form a point. This is tedious detail work. The grinder wheels give you this for free. You also probably want to do this after heat treatment if possible as the warpage on the teeth can be significant. I think that means using a grinding tool instead of an end mill and doing everything in a bath of coolant.
I'll probably come back to this in a month or two. I think the next iteration is to use a smaller end mill and better toolpaths and do something that is more wavy than pointy and possibly try a mix of small/large serrations.
The other thing I wanted to try is machining the serrations from both sides. This may be a bit of a pipe dream as I will probably bore of this rather than obsess about it.
