Subtraction - Week 5: Midterm


WEEK 1: Router Skill Builder

WEEK 2: Othermill Skill Builder

WEEK 3: CAD CAM and CNC Skill builder

Week 4: CNC Joinery Skill builder

TITLE: Midterm - Tripod

DATE: Feb 27, 2017




Last semester in the intro to fab class, I made five tripods(click to see the previous blog post), which were small and no height adjust feature.

In this midterm, I design to remake another tripod. On one hand, I want it to be part of my new project, on the other hand, I want to see the progress I made in fabrication area.



Well, dear readers, you can consider this part is commented out

So at first, let me introduce my new project briefly.

Last semester, I sort of failed on my physical computing project. It's ok, and the spirit of ITP is to embrace your failure. I talked to Tom about the reasons. Though there were a lot of problems, one of which really mattered, it's the timescale. In that project, I tried to do a physical expression of time-lapse.

Now I think I have a different approach about timescale. I will do a slow-motion installation and this time, I will start from a basic physical concept, the light.


So the final project will look like an astronomical telescope, which will be assembled by two parts, the tripod stand made by CNC due to midterm and a telescope made by wood lathe due to week 7 or 8.

Credit: Stevecoleimages/E+/Getty Images

Credit: Stevecoleimages/E+/Getty Images



I collected a lot of tripod images on Pinterest, a lot of them shared the same structure:

A triangle joint on the top to connect to whatever it holds, and three legs which may have one piece inside the other piece to slide up and down in order to adjust the height.

Also, instructable and youtube gave me a bunch of references how to make an adjustable tripod, which makes me sort of shame on myself that though I have so many references that I still chose the easiest one... but wait, this is a CNC assignment, make good use of CNC is also part of my consideration.

Well, I admit it was a bad excuse...



  • 4 x 4 ft Birch Plywood: it cost 37$, and I still have 2/3 of it. Bought from Prince Lumber, cost 1 day to ship to our floor
  • 3/8"-16"x1-1/2" carriage bolt * 3: 32 cents each, bought from HomeDepot
  • 3/8"-16"x2" carriage bolt * 3: 37 cents each, bought from HomeDepot
  • 3/8" stainless wing nut * 6: 1.18$ each, because they run out of normal one, what the hack...
  • 1/4" eye bolt * 2: 1.18$
  • 1/4" tee nut * 2: 1.18$
  • Sanding paper 400G: 6.37$, 10pk
  • Sanding paper 150G: 4.27$, 6pk
  • Wood finish: 4.98$
  • Brush: 1.15$
  • rubber feet 7/8" * 4: the smallest rubber feet I can find, one pack, 1.95$



Frankly, I don't really want to show these...

I did small tricks here:

First, I add a red guide rectangle here to help me located the origin, to save the material.

Second, I only drew one leg here. I realized that I can move the ZERO in CNC. If I need 3 legs, I can use the same sketch and only manipulate to move the ZERO 3 times. Also, it was better to cut one leg first to see if the tolerance is tolerable.

And the fact was, the hole for the screw was perfect(3/8"), but the pocket for the inner piece and the slot for the screw was too small, so I added extra 0.5" height to the pocket and 0.3" to the slot.

The other fact here was that once I added the radius to the rectangle, I could no longer change the height by input the value in the obj info widget since it's no longer a rectangle. Scale it by dragging would change the radius as well. Plus the shape drew by draw rounded rectangle tool is a little bit weird. So it's better to have an area to keep all the original shape before adding the radius to them.