i have been building a trailer and it's been quite frustrating drilling out the screw holes for my m6 stainless countersunk bolts. But I've got a lot of it done. I'm also fixing trailer hooks that came with screws. I tried drilling pilot holes as at first I tried to put the screw straight in with my impact driver but no joy. I got one trailer hook done then on the next my small drill bit broke Will this new bit set and lube oil help me do things a bit quicker https://www.amazon.co.uk/gp/aw/d/B0...rjXSL&ref=plSrch#immersive-view_1504326818154
Use quailty HHS bits, lube & a slower speed, shouldn't need a pilot hole for M6. If you got a Cromwell store nearby have a nosey. https://www.cromwell.co.uk/
You need a speed of around 1000 rpm for mild steel for 6mm hole & lower for a 7mm hole, any higher & you burn out (overheat/soften them) the drill bits, then you won't drill anything with them. Centre puch the metal will stop bit sliding, & plenty of lube, no idea what drill your using, I'm lucky enough to have 'Rachel' a large elderly 12 speed bench drill for any metalwork drilling.
Drills normally get hot when they are blunt. As others have said, get good quality drills. As a general rule a smaller drill bit requires a higher speed, look on the web for recommended drill bit speeds for the material you are drilling.
Everything that Kiab has said is correct. Chinese drill bits are a waste of time. Dormer are the best,but otherwise a good quality drill bit with Supacut or similar as the lube.
Poke you nose into a Cromwell Tools store, great bits Dormer, you can get then in jobber & stub versions.