Recently, I had a good excuse to finally make a “turner’s cube”. It’s a project where the end product serves little purpose, except maybe holding down papers, but where the process can be a good learning experience.
The first step is to do a bit of planning – with my winter-addled brain, this was a little more challenging than it should’ve been. Here’s what I ended up tacking on the lathe backsplash board, the perspective is a bit weird, but it did the trick:
In terms of construction, the first step is to hack off a bit of stock – this is 4″ aluminium round, I think 6000-series, but it doesn’t really matter for this project.
A 4-jaw chuck is used to make the cube. Unfortunately the jaws on our chuck weren’t long enough to hold the cube for the 3rd face, so I had the option of either spending a lot of time on making up a jig for that cut, or cheating a bit and using the mill.
The mill made quick work of flattening off some bits of the cylinder to make the part chuck-able in the lathe. I left some extra material, so that the final cuts would all be done on the lathe. This saved time on the milling operations, and made those nice concentric machining marks on each face of the resulting cube.
Although I designed the cube to be made with carbide insert boring bars, the ones we have available can’t handle the required overhang. For the larger tapered hole, I ground a 1/4″ HSS cutter to go in a boring bar holder. For the smaller conical holes cut out, I ended up using a small carbide grooving tool as a boring bar. Doing that required an adaptor, which I made with a bit of O-1 drill rod:
For a couple days worth of spare time, the cube was known as my “boring project”, as there was a lot of boring work to be done. In the end, each face required facing off, then a pilot hole, a 3/4″ hole to remove material, flattening the bottom of that hole with an endmill, then using a sequence of four boring bars to make the tapered holes. Each of those operations took a separate tool, so there was a lot of indicating in new tools in the lathe. Every-other face also included a 1/4″ hole to go through the innermost cube – I like the aesthetic, and it made turning the flat-bottomed tapered holes a bit easier.
Once three adjacent faces were done, I could see that the math worked out!
Finally, after a bit of tedious filing to de-burr the edges and corners, the end product was tested to hold down a piece of paper!