cutting inside curved corners

HI:
You can do it with with Forstner Bit the correct size, or with a template router bit. The straight work with a saw and clean it up with a router.

If you want to cut out a rectangle in the middle of a board with rounded corners, I’m thinking a jigsaw would work. You have to be careful in the corners not to snap the blade, but you can back off and approach the corner at a different angle until you get it completely cut out.

Hopefully someone with more experience can give you some insight.

Good luck

-- No, I don't want to buy the pink hammer.

Do you by any chance have an oscillating sander?

-- Gary, DeKalb Texas only 4 miles from the mill

Depends on the radius. for small radii use the forsner bit and a saber saw (jigsaw) to cut the streight areas and clean up with lots of sanding or a router.

-- Grumpy old guy, and lookin' good Doin' it.

I’m in the router camp. Similar to cutting the opening for a router table lift plate. If you’re careful with a table saw you can make a template pretty easy by cutting a piece of plywood or mdf a known size bigger on all sides (e.g. 3 inches, so a board that is 12×10), set your fence to 3 inches and bring the blade up through the board till it gets close to a mark made on the top, proceed to rip the board till the cut come close to a stop line at the end of the board then shut the saw off and repeat this step for the other three sides. be sure not to cut all the way to your stop lines, last thing you want is a loose board to get jammed in the opening. Use a little hand saw to cut the remaining bit and you now have your router template that you can use with a pattern bit with. You can also use stop blocks on the fence to help with starting and stopping. I understand this trick for making a template is a little scary, so don’t try it if you’re not comfortable with it.

-- "At its best, life is completely unpredictable." - Christopher Walken