I need to make a hexagonal prism, ~70mm long, ~30mm across flats and drilled centrally along the axis; the material isn’t terribly important; alloy would be nice, as would acrylic, but it could be probably be made from a fairly fine-grained, stable hardwood such as beech or lime. I’m a moderately competent craftsman, but not an engineer by any means; tools I have at mu disposal include a fairly comprehensive set of woodworking handtools, a slightly more limited set of metalworking handtools, an electric drill (sadly handheld, not a pillar model), a rather cheap-and-nasty smallish drill-powered woodturning lathe, plus a few other things.
The dimensions themselves don’t need to be terribly precise, but the end result needs at least to be regular in proportion.
Suggestions? (I’m also open to the idea of cannibalising a suitable part out of some readily-available manufactured item, if someone can suggest one)
No, a prism is just a shape with two matching faces at the ends and parallelogram faces joining the edges of those ends. (I even remembered that before looking it up!) The glass rainbow-makers you’re thinking of are called prisms because of the shape.
This would be easier if you told us what it’s for.
One approach you might consider is one I used to build kaleidoscopes many years back. Take some thin pieces of wood and bevel the long edges 30 degrees. (A router with a chamfer bit would work well for this.) Glue up, and you have your prism. Then fashion some hexagonal end pieces with the holes drilled. If you need structural strength, you could put a steel pipe in the center of the hexagon. Or you could fill the center with resin and drill it, I guess.
Actually, if you look for “coupling nut” in the same place, you can find essentially the same thing with a threaded hole already drilled. They have lots of sizes.
I can’t tell you exactly what it’s for, as it will be a component of a device I hope to patent (if it works), but the component itself is to be the core of a scanning mirror - the sides therefore need to be quite accurately parallel, the cross-section needs to be quite regular and the drilled hole needs to be quite central. It won’t be subjected to incredibly high spin rates, so the materials and construction can be quite basic.
To be perfectly honest, it doesn’t even necessarily have to be a hexagon; I could probably make an octagonal section piece more easily by taking the corners of a square-section block.
What are your +/- tolerances on the 70mm long /30mm across flats? And also what diameter are you looking at as far as “drilled centrally alonge axis”? I think that something like this could be found and or fab’d right at home as long as yer not wanting glass or crystal etc. with tight specs.
The tolerances are really quite broad; I intend to build the rest of the prototype around this component, so 100mm long and 50mm across the flats wouldn’t be a problem at all. The axial hole needs to be somewhere in the region of 4mm dia so that it can be mounted directly on a fairly standard motor assembly - this is a little more critical; I’d just buy some big hex nuts and stack them up, but the problem would then become one of trying to drill a hole exactly central to whatever I mount them on.
I can’t help feeling that there must be some bit of cheap hardware out there that I could just cannibalise, but I’ve been looking around for a while now and I haven’t found it yet.
