A #76 is around .50 mm, which is my most-used drill size for all my piercing (sawing) work. I use dental drills (they last forever) in a small standing table drill. If you use an Optivisor (magnifying glasses), you can see exactly how the bit is entering the metal and if there is going to be unwanted bending. Start with a peck, and when you see it cuts well, go in smoothly and gently, all the while with an eagle eye on the drill tip. The cutout scrap should be a single, long ‘curl’ if the bit is cut properly and you handle it smoothly. I use wax as a lubricant. Beeswax has always worked best for me with drills, but I often use a simple candle.
Having said that, I strongly recommend learning how to grind the bit yourself! Once you get this skill down, you will kick yourself for not having done it sooner, as it takes only seconds and saves you a ton of money and aggravation. I learned by looking at a big fat drill bit to clearly see the way the planes of the curves should be and just copied it in super-miniature on my tiny bit. I do the cutting on a flex shaft separating disk, touching the bit ever so gently with a slight twirl to get the curvature:
This is one of the many skills that all old goldsmiths had in the past. I was literally in shock the first time I did it when I saw how smoothly and easily the drill cut after sharpening–like butter, with a long, single curl of the ‘waste’ material which can easily be recycled. I would be more than happy to show you how to do it if you ever find yourself in Jerusalem and care to stop by for a visit
, but it would be well worth it to go to someone local even if they charge you for a lesson. You will more than make the money back on saved drill bits…:-)…
Janet in Jerusalem