A common bench-press assistance movement is the board press, which involves stopping the bar short of full depth by putting a board on your chest to limit the bar’s range of motion by some amount (based on board thickness). To perform the movement safely and consistently requires a helper, and the boards take up a good bit of space in the gym.
An alternative to placing a board on the chest is attaching something to the bar that serves the same purpose. Some products exist on the market that serve this purpose, but they are expensive.
The challenge was then cutting the bar channels along each dimension. The one purpose-made product I’ve seen looks like it was cut by wire EDM. I played with the idea of making a hot-knife/wire EDM rig out of a coat hanger and a power supply, but guiding the cut would be difficult with that method. I instead used a large vertical band saw (needs a big throat).
To guide the cut, I modeled the blocks in CAD and printed out each ortho view 1:1 to use as a stencil.
After cutting out the bar channels from the paper with a razor blade, I used the stencil to spray-paint the blocks, marking the cut areas.
Then the cuts were easy. I made my initial pass through the center to cut the circular end (pictured below). Then I cut the straight walls (slightly narrower than the cylinder diameter) and finally, the lead-in chamfers.
The two blocks provide six different thickness/offset options: