You know you have achieved the proper speed and pressure when you are CUTTING. Long unbroken strands of metal are how you know you are perfect.
Wood does not matter but when drilling metal speed pressure and use of cutting fluid are critical unless you want to quickly ruin your bits.
Start slow and gently up speed until you are cutting perfect shavings.
Cobalt for drilling in steel. Period. (not cobalt coated)
HSS is for wood and Aluminium.
Coated bits are a waste of money, just get some high quality HSS or Co.
Another CO that makes awesome drill bits is Chicago Latrobe.
P.S. Drill doctors are for people with time on their hands. Those that use their time to make money just respect and use bits properly and buy new when needed which is not often if you use bits correctly.
