The type of bit is not as important as avoiding heat.
I think cobalt bits are excellent but you can use almost any bit as long as it is sharp and fresh. Drill bits must be looked at as perishable items, when you are considering using them for anything beyond the softest of materials like wood.
Key points:
1. Sharp fresh drill bit
2. Very light centerpunch if any- work hardens the piece and makes drilling more difficult; is tradeoff, don’t want your bit skating all over the surface trying to get started; can work with a carbide scribe to scratch enough of a starting dimple to get going most of the time. Better yet use a drill press wherever you can!
3. Slow speed (machinists work in surface feet (or meters)/min, and then calculate RPM based on size of drill; if you’re not that ambitious just go real slow targeting 100-200 rpm; if you’re using a vsr drill, gauge that but what percent of full trigger you’re using).
4. Liberal use of cutting oil, or some lubricating oil (no H2O) on bit and in the hole, drizzle more during the drilling
5. Frequent stops to clear chips.
Good reference here:
https://www.bssa.org.uk/topics.php?article=194And to quote the sage words of Matt Groening, Simpson’s creator, but before that wrote a comic strip called ‘Life in Hell’, “If you drink, don’t drill.”
