So I was up way late last night in making some spring clip attachments of top hats to Mac 250 fixtures. Must have broken about upwards of twenty drill bits, this following three or four center punches in just making the initial holes. Fairly easy to bend and cut a Menards type sliding door screen spring clip to that which I needed and they were already black in color. Sure just punch the initial hole with the center punch, pound it flat, pound another hole with pointed punch from the other side, pound flat again and pound again hard in now opening up a hole. Than drill away once the hole is there. Step up the drill bits 1/64" at a time until at #30 size for a rivet. Sounds simple enough, weaken the metal, punch a small hole for setting it up and drill away. Didn’t work so hot on these couldn’t be more than 1/32" thick spring clips I was attempting to rivet to the top hat flange. The normal 82 degree tip angle black oxide coated drill bits cut great for the first hole, than not so well on the second or not much more if at all and much less for following holes in stepping up my drilling. TICN coated etc. bits didn’t work so well either. Cutting oil was even less effective yet. Only at the point when breaking drill bits that suddenly punched thru the material did I note something. A broken drill bit still in the chuck almost no matter what type in not mattering as long as if had a flute left seemed to drill thru the spring steel better and easier than a slightly dull bit. Why is that that a broken drill bit would cut thru spring steel better than a pointed drill bit? Other more optimum ways to open up a rivet hole in the spring steel? Drill speed? I was at about 1,750 RPM on fresh cordless batteries and more likely normally about 1,200 RPM.