ITP Blog

Subtraction - Week 4: CNC Joinery Skill builder


WEEK 1: Router Skill Builder

WEEK 2: Othermill Skill Builder

WEEK 3: CAD CAM and CNC Skill builder

TITLE: CNC Joinery Skill Builder - Wooden Heart

DATE: Feb 15, 2017



This week's assignment started to become a little harder. 

I did a lot of mistakes at first. After I reviewed the whole process, I think the main reason is that I didn't really understand the tolerance part.

But also, I have to admit, there existed some stupid movements:

Forget to mirror the piece.

Forget to hold the small piece so it won't bump out.

Over Sanding.

And hammer it to fit and break...

/* Now I am not in the emotion of updating this post.

That's why it's in progress... */


Here is the new one I made on Sunday, I measured more than 5 times to ensure it fit, but it still didn't fit quite will. I have to use the hammer again. Before the cutting out, I screwed the pieces on the spoil board. Nailed it and finally did something right!







1. The tolerance for joint is pretty small, measure as many as possible. I think our CNC has at least 0.005“  errors (shape, not height). I may not make it clear. I mean my joint is a little bit bigger in shape, not thicker. Next time I will try to downsize the shape in Vecterworks.

2. The materials matter in this case, plywood is more likely to be broken when be pushed into the slot.

3. I cancelled the break through when pocket the extra thickness. But I'm not sure if it's right to do so.

4. It's OK to pause the CNC and use the joystick to move the bit away! I tried this in order to screw my pieces before they were cut out.

5. We could screw the big pieces. How about the small pieces? Is there any trick to hold them to avoid bump out? I checked Phil Guo's blog post, he slowed down the jog and used his hand, which seems not a good idea to me.

6. I did a little research on the miter joint(butterfly joint) and find a famous woodworker named George Nakashima.

George Katsutoshi Nakashima (Japanese: 中島勝寿 Nakashima Katsutoshi, May 24, 1905 – June 15, 1990) was an American woodworker, architect, and furniture maker who was one of the leading innovators of 20th century furniture design and a father of the American craft movement. In 1983, he accepted the Order of the Sacred Treasure, an honor bestowed by the Emperor of Japan and the Japanese government.

He used a lot of miter joint in his design. Beautiful.

 Butterfly Gate by George Nakashima

Butterfly Gate by George Nakashima

 Mira Chair by George Nakashima

Mira Chair by George Nakashima

 Sunset Base Table by George Nakashima

Sunset Base Table by George Nakashima