This stool has three legs and is stable even on irregular surfaces. The front leg extends upward, making work height adjustable. The pipe supports either a small round turntable upon which one can make jewelry and small sculptures, or a rotatating "T" top for use with a drawing board. The stool is light weight and easy to carry.
Construction of the stool involves some welding.
Step 1: The Pipe Frame
This stool was made many years ago and was never painted. Where the pipe was welded, the galvanized coating was damaged and the welded areas are rusted. Use of a rust-preventive paint after construction means more work, but will extend the life of the stool.
The dimensions of the pipe depend on the dimensions of the user. Think of a bicycle seat suspended in the air at a comfortable height. Then cut your pipe the right lengths to connect the seat with the ground.
Step 2: The Seat
You might be able to just find a comfortable bicycle seat and weld it to the stool's pipe frame.
I cut a piece of plywood to the shape I wanted and upholstered it with some mattress foam and vinyl material. The vinyl was folded over the foam and plywood and stapled to the bottom of the plywood.
The Plywood is mounted to the pipe frame with three brackets I made out of PVC pipe, heating the plastic to form the brackets. If you do that, make sure you have good ventilation and try not to burn the plastic. You could also buy metal brackets that do the same job.
Step 3: The Feet
To protect the floor surface, the bottom ends of the pipe legs are covered with 3/4" PVC pipe caps. If I recall correctly, I may have had to heat the plastic a little to soften it and let me jam the caps over the ends of the pipe. Heating would have been done with a propane torch, holding the caps with pliers. Try to soften the plastic slowly and carefully, to avoid burning it. You might get lucky and find caps that fit perfectly without heating.
If the feet caps wear out someday, they are easy to find and easy to replace.
Step 4: The Turntable Top
The turntable top was made out of some scrap plywood. A tight-fitting hole was drilled to make a socket for a short section of 3/4" diameter pipe to enter. It was glued in place. The other end of the short section was sawed with a hack saw to make 3 "fingers". The fingers were then hammered over a piece of 1/2" pipe to conform to its shape. A hose clamp tightens around the fingers and holds them to the 1/2" pipe that telescopes up from the front leg.
Loosening the hose clamp allows free turning movement for the turntable. Tightening the clamp keeps the top from turning when you want a more solid work surface.
The same sort of telescoping connection with a hose clamp is used below on the vertical support pipe, where it exits from the top of the front leg.
Step 5: The "T" Top
I haven't used my stool for drawing in a long time and have lost the "T" top. I no longer have welding equipment to make a new one.
The basic idea can be demonstrated using PVC pipe and a "T" connector. The original "T" top was made out of 3/4" EMT pipe and fit loosely over the top of the vertical 1/2" support pipe.
A glass marble was glued to the top of the support pipe. It reduced friction from the "T" rubbing on the top of the pipe. The marble also creates less friction in the movement of the turntable top.
Given the loose fit of the "T" top on the support pipe, the top spins freely. It always conforms well to the angle of the drawing board and gives good support for the board.