Carbide drill bits are absolutely necessary when drilling stainless steel or other high-density materials. No other drill bit can handle the job.
Not entirely true. This is a page from the above link:
NEXUS Drills
For years the name in stainless steel drilling has been synonymous with OSG's EX-SUS-GOLD drills. Well OSG has raised the bar with the next evolution of Vanadium High Speed Drills, the NEXUS. This latest product from OSG features a unique 40 degree helix, coupled with a sharp thinning point designed to; reduce work hardening, improve finish, and eliminate exit burrs. The NEXUS also features WD1™, OSG's latest new development in coating technology for drills. Higher oxidation temperatures, better adhesion strength, and elevated hardness allow the NEXUS to run faster than its predecessor without any lost tool life. NEXUS is designed to improve efficiency through faster speeds and improve tap performance by reducing work hardening in the hole.
Improper cutting speed is where tool life is most wasted and can be determined by the following formula:
CS (cutting speed) X 3.82 / DIA. = RPM
30 sfm for stainless and 80 for mild steel would be good starting points when hand drilling. For example a 5/16” drill in stainless steel should be spinning 367 RPM (+- 50 RPM) or 979 RPM in mild steels. By ignoring this and spinning much faster excessive heat is generated which is quickly fatal to the temper of the cutting edge. The quality of the drill/tap ultimately decides the SFM the tool can be run at so with cheap stuff going slow is the best defense to preserve tool life. Lubrication never hurts and even a drop of motor oil will help but a can of Rapid tap or similar product will pay for itself many times over in keeping cutting tools sharp. Here’s a chart with recommended surface feet per minute for various materials:
http://www.winsloweng.com/articles/drillChart_content.htm
