OK, I checked Thunderbird supply and they don't stock them. Stuller doesn't show them on line, but do show sharpeners for them. I didn't create an account for RioGrande, so I wasn't able to see their offering.

Gravers are small hand pushed tools used for engraving work. It is all but a lost art now as few jewelers do anything other than template tracing or CNC engraving. The Gravers came in a a wide range of tip designs. 1/2 circles, lines, multi lines, square(the ones you are looking at), as well as others. Each design came in numerous sizes. All were for cutting into a surface.

I've seen responses about a drill in a square tube, these are mortise tools for wood working and they basicly broach a square hole and the drill removes most of the material in the process. They would not be very sucessful working with balsa as the wood is so soft the it will crush before the square part can cut it. Even it it is able to cut it, the distortion would be great.

What was your intention for the tools? IE what did you want to accomplish with them. The drawing you showed is a clasic graver tip. When it is very sharp, it easilly cuts a 90 degree cut, edge down, into gold or silver. It is less effective on softer wood like balsa, but if it is lapped with a very fine stone and the stropped, it will work. Cheaper wood working gouges will also work, but again a proper sharpening is mandatory for success. For a penetrating hole, your best bet is to drill to size and then use a jewelers 4/0 blade to square up the hole, or use a small needle file to square the hole. The later is what I use to square up the holes for Robart Hing points.

Lets us know what you want to accomplish with the tool and we can give a more focused response.

Don