Help with square pocket?

Hello all. First time poster, long time reader/follower. I’m starting to use my shapeoko for more things, and I wanna make a chessboard. Everytime I make a pocket in CC the corners are rounded… Only way I can keep em sharp is to do an advanced V carve, but that cuts the outter edges at an angle… any advice on what to use to keep the corners square and not rounded, but have a straight down cut? Tryin to make a chessboard and fill the black squares with epoxy. But I need the squares to stay dimensional when I surface the board after the fill. Thanks! -Roger

You can’t make square pockets with a round bit (except with the v bit). Best way I’ve found in the past is to use a chisel to square off the rounded portion.
Also a smaller endmill will make the rounds less noticeable. If you’re using a 1/4 inch bit, it’ll be a lot more noticeable than a 1/16 inch bit.


Maybe use it to your advantage. Cut out the rounded corner squares for both the black and the white squares, and leave 1/8" between the black and white cavities. It will look intentional instead of a work around. Maybe you can make a pattern instead of a solid square, like this?

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Cut your pockets with, say, a 1/8" bit. Then cut the corners with a 0.2 mm bit. Do this by creating an SVG that isolates the corners so you don’t spend days covering the main pockets again.

Or, square up the corners with a chisel.

Or, better yet in my opinion, do the board out of two divverent woods as a v-carved inlay. My preference for this is walnut and maple.

If your board is big enough, then this type of corner chisel is very easy to use. I have one and use it a lot (and am a sucker for all tools, especially ones made on the us).

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The only way to make square corners would be to alter the geometry and possibly use multiple pieces — gluing up individual squares would work well, or you could do the Kumiko thing and cut and glue up lots of tiny pieces, or rotate the project 90 degrees and cut it in sections from the front of the machine.

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Thanks for the replies. I think I’m just gonna have to chisel the corners. I’ll use an 1/8" or 1/16" bit the cut the outline and then clean it up with a chisel. Just wanted to know if what I wanted to do was possible. Thanks-Roger

Well, you can cut square inside corners with a CNC but you’re gonna need a couple more axis. One to tilt the bit & spindle (use a 90* Vbit) and a second to rotate assembly about Z. Think of the way your wrist works if your hand could hold the spindle and bit.

A bit more than a stock Shapeoko can do.

The multi-bit method described above and a nice sharp chisel will get you there. You can use the tip of an engraving bit to give you “knife lines” to guide your chisel if needed. Keep in mind that the bevel of the chisel will try and push back into the work so you don’t want a lot of material in front of the bevel. Take small bites.

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