I’m building the Stumpy Nubs Box Joint Jig for my new table saw and it has a crank wheel attached to the end of a threaded rod. It’s kind of a clever idea with a captured 1" nut.
The instructions say to bore a hole, trace the nut and use a chisel to square the corners. It also suggests you could drill some lightening holes.
But I have a CNC router. So I have to make it better.
I whipped up a quick 2D drawing of the wheel and imported it into CamBam to generate some G-Code.
I haven’t really used my Shapeoko 3 at all since I did the XL upgrade so I figured this would be a good test case, since it didn’t really need to have any precision to it.
I asked G-Wizard what the speeds and feeds should be for a 2 flute 1/4" diameter end mill taking 1/4" deep passes in plywood and it said ~23000 RPM and 100 IPM (and it wanted me to go faster.) Wow, that’s a pretty fast feed rate, but okay. So I programmed it up and hit the button. And then promptly hit the stop button.
100 IPM is pretty aggressive. The machine was shaking the table, and I have it on a pretty stiff table. So I edited the file and changed the feed rate to 60 IPM. That still seemed pretty aggressive when it was running, but I let it go. It hogged out the parts in short order with no real complaints.
The parts turned out pretty well, but I had extended the end mill quite a bit so there are some visible signs of deflection. Not that it matters for this application, but if I was doing precision work I’d need to do a bit of tuning.
On the plus side, the 1" nut is a perfect press fit in the hole, so the results are just what I needed.
Here are some pictures:
Simple fixturing. Blank is screwed to a piece of MDF and I left tabs when machining the outside. Cutting the outside was the last operation.
All cut out.
Made a pair, the nut gets sandwiched in-between them. I milled the 1/2" hole for the handle about 1/8" deep so both parts are the same. Then I used a 1/2" Forstner bit on the drill press to finish drilling out the hole in one half. I’ll glue a 1/2" dowel into the hole for a handle.