Circles larger than the cutting area (the easy way)

Building a rotating bookshelf for my youngest and thought of an easy way to cut the circular shelves.

I have 6mm holes in my spoilboard, so I simply cut a 6mm hole in the middle of my square stock. Then I connected both with a metal pin as a pivot point. Then I moved the router in position above the stock and while I moved down the bit very slowly I started rotating the stock by hand. For the finishing pass I moved the bit slightly closer to the pin and kept turning the workpiece.

Video.

How it will look when done:

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That’s pretty cool. I’ve seen that same technique using a table saw.

And a band saw and a router table, but for reason, I’ve never thought about using the cnc like that. Thanks for sharing.

Yeah, I kinda think of it as an inverse router table, which can be beneficial from a dust extraction perspective as well.
I guess you could use a flush trim bit with a bearing the same way.

Now what the CNC version could do for you is a wavy pattern on the circle, though you might want to rig something up to rotate the piece at a steady speed…

I’d not be confident in my ability to do this. I’d probably work with registration holes and machine 4 quadrants individually, each time with proper work holding.

I’m actually planning to do this for the dowel hole pattern I want to machine into these circular shelves. Stay tuned!

Started adding bolt and dowel holes to these circular shelves and thought of a (somewhat) easy way to do this with the CNC even though the shelves are larger than the cutting area. I basically rotate the workpiece using the CNC.

Given that I need to machine four identical quadrants, I machine one, then for the last feature I just run the bit straight down into the workpiece and turn off the router and remove the clamps. I have added a pause command to the GCODE at that point. Then it does a 90 degree arc move with my pivot point at the center, rotating the work piece as it moves. Then I fix the clamps, turn on the router and resume the gcode, letting it mill the last feature. I repeat this 4 times.

Video showing the MPCNC rotating the workpiece.

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Sets piece up, places dowel, moves the head the legnth of the radius. G92 x0 y0 z20. G1 z0 f1. 20 minutes and 20 spins later, and you’re through 3/4 stock. Obviously I’m used to 60+ inch circles, and hardwood stock.