I wanted to make a book shelf, so this is my design sketch:

Then I drew this CAD file:

The way to draw the oval-shouldered halving joints is tricky. I drew a square shape first, than the four arcs could be symmetric.

I bought this 1 in. x 12 in. x 6 ft.  pine board at The home depot. It’s quite long, so I had to cut it into three pieces to mount on the CNC spoil board.

Then prepared to cut:

But terrible things happened.

When the drill bit cut the first pocket, the depth was correct in the beginning, but it became deeper gradually, then totally cut through.

I hit the pause button to check. And I realized the wood top was inclined towards the left!!!

The thing that sucks most was after I putting the spoil board back into the bracket, it was still not horizontal… All the cuts were deep on the left but shallow on the right. I also made a mistake in the meantime… I should reset the origin position of Z axis.

Finally, because of the accident, the parts couldn’t fit.

Another problem was, I forgot to modify the round corner in the CAD sketch.

The sad thing is shop closed on Monday, I can’t make it one more time. I corrected my CAD sketch like the picture below. I’ll remake it on Tuesday.



I have finished this new modified one. This time everything worked well. The only problem was I should add more tolerance at the joint, because it’ll be too tight if I use the exact measure. I finally solved this problem by sanding the joint parts.



1. How to remove a stuck bit

Grab the drill bit with paper or towel, knock the upper part of the bit while pull it down. Repeat this knock several times.

2.The origin of the CAD file is in the center, which is exact the same with CNC. Be careful when import the file from AI, the origin may change. The solution for that is copy the path into another new CAD file.