I always wanted custom knobs for my Profitec 700. But I bought the machine used and it had stock ones on it. Custom ones were just too steep a price for me, so I kind of thought that was that. The after a few years I randomly got access to some free slabs of 2" walnut. I figured I might possibly be able to turn these into knobs for my machine.
It took a while for me to figure out how to source the materials for the metal inserts. I figured out that they were M14 and M8 thread. But finding inserts on some sites that looked suitable, but they looked like they would cost in upwards of 40-60 dollars which seemed really steep. I ended up buying all my inserts for $16 total off of ebay. I was a bit apprehensive that it was just not going to be what it said it was, but it all worked out.
The hardest thing for the inserts was that they needed to be a very specific depth, and that meant that I had to grind off 5mm for both of the knobs. Here is a ground down insert with all the fittings on the machine to make sure it was not too long.
I ended up having a friend who had the drill press and other equipment that I needed to get the basic shape out.
Drilling the center hole seemed easy enough. I decided to use the stock end caps, so one side had to be a specific depth for the insert and the other side had to match the 17mm hole as closely as possible
I kind of ran out of ideas for the bevelled part. But I actually ended up chucking the knob into the drill press and used a 60-grit orbital sander which worked incredibly well.
I felt like a teardrop shape would be a real challenge but as I was working on it I realized a kind of wedge shape might be really interesting if I could pull it off.
I then treated the knobs in oil after using some JB weld to fit the inserts.