The purpose of this head is to allow you to rotate your camera about its nodal point / exit pupil, letting you take a series of photos in all directions, without any parallax error.
Once you take the photos, you can process them through various pieces of software to produce a single image that can cover up to a full 360° - including the ceiling and floor underneath you.
I made my head primarily out of 20x20mm T-Slot aluminum that I purchased from Misumi. Instead of designing it all in advance and having Misumi ship me the precise correct length pieces, I have a couple meters of the material that I keep at home for various projects like this.
Fabrication of the head involved cutting the T-slot material to the right length, deburring / polishing the ends, cutting a few holes, and tapping screw threads into a piece of steel for attaching it to my tripod.
I made it in the metal shop at TechShop
Step 1: Understanding the Design
Before you cut anything, you should understand the design and consider what changes, if any, you need.
I ended up making the pieces a lot longer than I needed to. I will likely go back and shorten many of them.
You should also of course determine what hardware you need. Misumi has a very, very broad range of hardware. The prices vary enormously. There are some really nifty components that can add a lot to the cost.
For the nuts, I used spring-loaded post insertion nuts. This means that they don't slide around, and you can insert them in the middle of a rod - they are quite narrow. The standard nuts must be inserted at the end of a rod, so if you have something already assembled you may need to take it apart to insert a nut.
If you don't already know the distances needed for your camera's exit pupil alignment, you may want to make a longer version first and then chop off excess material.
Step 2: Cutting the T-Slot Material
T-Slot material is very handy. It's extruded aluminum that is quite strong and light. There are numerous vendors of it out there. Some companies sell kits with pre-cut lengths, other companies expect to sell it to you in custom lengths or extremely long pieces for you to cut for yourself. Misumi does the latter - their target market is industrial factory type work.
I used the horizontal band saw at TechShop to cut the T-Slot tubes. It is fast and easy. The biggest issue is that you can't cut a small piece into two small pieces - the saw clamps somewhat far from where it cuts. So you can cut a tiny piece off a long piece without trouble, but if you only have a short piece left you may be using a different saw.
After I cut the pieces, I looked at the ends, and they were sharp and full of fragments. Off to the disk sander. Make sure you use one that's appropriate for aluminum - some cutting wheels do not work properly with aluminum. I started by polishing the end flat. Next, I rounded off each of the four long sides. Only took a second or two of touching for each side. Then I lightly tapped the corners to the sander. Then I lightly tapped the inside corners to smooth off the edges there.
After sanding, you'll notice that there are metal fragments inside the channels of the T-Slot. You should wash them out. The cutting fluid from the horizontal band saw also helps the fragments get stuck.
Step 3: Drilling the Holes
I drilled a hole large enough for a 1/4-20 bolt through two of the T-Slot rods so that I could make a pivot point. This allows me to point the camera up and down, letting me get all the way to the ceiling.
I simply clamped the rods and drilled. I used a metal washer in-between the rods, and a nylon lock-nut at the end.
I also drilled a hole in one of the right angle brackets for the camera mount point. The standard holes in the bracket were too small for a 1/4-20 bolt to fit through. You will notice that I used an off-center hole. I have a bracket on the bottom of my camera which results in the camera having 1/4-20 tripod holes at different points.
For optimal alignment, the camera optical axis should be aligned with the pivot hole. the standard tripod hole on your camera will probably be lined up with the optical center. This sounds good, but it actually makes things difficult. If you were to drill a hole in the T-Slot rod, then you can't shift the camera closer or farther from the rotational point. Every lens you use will have a different distance. I think the best plan would be a quick release mounted to a right angle bracket, such that you can loosen the screws and slide the assembly forwards or backwards.
Step 4: Making the Threaded Rod
I needed to attach this whole assembly to the tripod. Based on the weight of my camera, and the distance from the attachment point, I expect the force to be significant. Aluminum threads concern me.
I grabbed a piece of thick scrap steel, and cut it using both the horizontal and vertical band saw. The horizontal band saw is very fast, but you have to clamp it properly. I was only able to make the first cut with it. Later cuts were made on the vertical band saw, which took a lot longer and involved me pressing a lot harder.
After cutting it into a rectangle, I then used a sander to smooth the edges and get rid of any sharp areas. Then, I cut four holes. Two for the standard Misumi bolts to attach it to the T-Slot, and one each for a 1/4-20 and a 3/8-16 tripod thread. I then tapped those holes. Tapping in steel is slow and tedious.
(1/4-20 is the standard thread size for cameras. Interchangeable heads on tripods usually use 3/8-16.)
Step 5: Assembling It All
The spring loaded nuts can be a bit tricky to get in. They're easiest to install by sticking them in at one end and sliding them. I often put a bolt in one, and used the bolt to slide it along.
I bought some cord shelf lining material at Orchard Supply Hardware, and glued it down along the rod where the camera went. I also used an angle bracket as a lower end stop to prevent the camera from going down too far.
I kept the tension of the pivot fairly tight. The camera can almost stay there on its own.
For the primary camera tripod mount connection, I put a long 1/4-20 bolt into my camera, and screwed it in gently until it wouldn't go any farther. Then I very slightly unscrewed it, and twisted the first nut up against the bracket. Then I twisted the next nut hard against the first one, locking them together. This ensures that you know that you have screwed the camera tripod thread in far enough.