How I Make Adjustable Pivot Points for Rolling Ball Sculptures

Here’s how I make adjustable pivot points for my rolling ball sculptures using aluminum round bar and a simple drilling jig. These pivots let me fine-tune the fulcrum point of moving elements while I’m building and testing a sculpture.

This super nifty jig helps me drill parallel holes through aluminum round bar. It would be nearly impossible to get them perfectly aligned without this tool. I’ll show you in the next few pictures how I use this indispensable tool. I sometimes use a piece of small steel tubing for my pivots, but this type gives me the ability to adjust its position when I need to fine-tune the fulcrum point of a moving element.

This is a blank cutoff aluminum plug. It’s already been faced with my lathe, so it has nice flat ends.

Once faced, I take the part to my milling machine and cut a flat into one side. The flat keeps the round part from spinning in the jig so the holes remain perfectly aligned. If the part moves while I’m drilling, the drill bit can bind, making it difficult to get a clean, straight hole through it.

The bolt on the side of the jig – sticking out the left side – holds the piece in place on the flat so it will not spin while drilling.

Here it is under the drill press getting the first hole drilled. The two black inserts on top are drill guides made from tool steel. They keep the drill bit straight and accurately positioned while drilling. If the guides were simply holes drilled into the aluminum jig, they would eventually wear from repeated use and become sloppy and inaccurate.

Here’s the finished part. The holes are drilled through it, parallel and straight. The only thing left to do is press the bronze bearing into the center.

At the top is a finished pivot used in a tipping arm on one of my rolling ball sculptures. Drilling accurate, parallel holes through round stock can be difficult, which is why I made this jig. It gives me a simple, repeatable way to make these adjustable pivot points whenever I need them. These adjustable pivots are just one of the many small mechanisms I build by hand for my rolling ball sculptures. Each sculpture combines several fabricated parts like these to control how the marbles move, change direction, and interact with the kinetic elements.