In message , Dave Baker
writes

Drill bits have a wide range of utility. Even cheap ones will be close to
nominal size and in any case hole size is not critical to a thou or so when
drilling and will vary more due to the machine, the chuck and the speed and
feed than the tool. What you get by paying more is longer life and the
ability to machine tougher materials.

So for occasional or hobby use cheap drill sets are usually fine and in fact
are often pretty good quality. You might not get many holes out of cheap
ones before they go blunt but if you only want to drill one hole it doesn't
matter. In high volume production environments the cost of tool changing and
setting up again will far outweigh the saving on cheap items so you buy the
best.

One drawback is that the shank is left hard and likely to slip in the
chuck under extreme load. I guess drills from SKF/Dormer etc. are part
annealed to avoid this problem.

regards

--
Tim Lamb