It is referred to generally as ‘the inside corner problem’ - because the cutter is round, when it cuts into the corner of a square, you end up with a radius instead of a nice sharp corner.
To overcome this limitation, you can do what is known as ‘overcutting’ the corners, which will provide relief to the places that would have otherwise been rounded over. When you’re placing two pieces together, in a method such as this slot and tab design, without the overcut corners, the pieces will not fit fully together.
Thanks for the info. I called it a dogbone, but I guess it’s actually a Tee. The smallest radius of Tee that you could use would be equal to the radius of your endmill… so 0.125 for the 1/4" mill? Or if you used a dogbone shape, you could use half the radius of your endmill, or .07? I think I’m visualizing that correctly.
Alternatively, you could not do the relief cuts at all and use a square file or small chisel to square those corners.
Dogbone or T either way it is accomolishing the same thing. I prefer the look of the T over the dog bone, but that’s just my preference.
You are correct about the minimum radius, and your 0.07 number is also correct to get the minimum overcut possible for a 1/4" cutter. I use the built in corner treatments in Carbide Create, where you can just select dogbone or tee and then input the radius you want to use.
You can absolutely use a small chisel or file to square up the corners, I prefer to let the machine do that sort of work, but the tradeoff is of course the design aesthetic. Not everyone is into that sort of look.
Another option is to use overcut corners, but do them blind, so the joints aren’t noticeable from the outside.
The dog bone openings is a decoration opportunity. If 100% of the dog bone holes were 1/2 rounds, 1/4" walnut dowels could be split to make some filler pieces.