Well done. Great to find ways to re-use what is basically a useful set-up or tool.
Your post reminded me of something that I find handy when wanting to dril straight holes - often in outdoor (away from shop) situations...
I got one of these:
I got it via telephone order (an 800 number) from Big Gator, the company distributes them in N. America. $25 plus handling/shipping.
Mine is in English measure, but they offer ones in metric, too. So what do I lik about it? It guides your drill bit perpendicular to the surface of the workpiece. The one I bought has 17 graduations, between 1/8 and 3/8 inch diameter. It's made of a very hard steel alloy. It's compact, hence fits nicely in even your smallest away-from-shop tool box, or fits well into a pocket of your tool belt. And (being ferrous alloy) can be stored on a magnetic tool holder on a shop wall, with other hand tools.
Okay, I was originally contemplating using one of these with just carpentry/woodworking applications - and it's good for those, but also works nicely on steel tubing. Due to the V-groove running across the bottom, it fits especially well on smaller tubing (say, 1-inch o.d. and smaller). It can be hand held, or clamped in place temporarily, hence in effect it enables you to have something like a 'drill press' (straight, well-aimed holes) wherever you go.