The tendency of stainless steel to "work harden" makes it difficult to drill. Work hardening occurs when heat generated by cutting, bending or drilling the metal causes the heated area to harden. The localised heat generated while drilling causes work the sheet to harden faster than other types of metal working. Controlling the build-up of heat and using a drill bit designed for harder metals will allow you to drill multiple sheets.
Select a cobalt drill bit matching the required hole size in the chuck of a drill motor.
Coat the end of the drill bit and the surface of the stainless steel sheet with cutting fluid.
Set the tip of the drill bit onto the surface of the stainless steel sheet. Push the drill motor firmly toward the surface of the metal. Pump the trigger of the drill motor to slowly turn the drill bit. Apply additional cutting fluid to the tip of the drill bit if you notice smoke coming from the area you are drilling. Lighten the pressure you are applying on the drill motor when you complete the process of drilling the hole.
Secure a countersink drill bit into the drill motor. Apply cutting fluid to the countersink bit. Set the tip of the bit into the drilled hole. Quickly tap the trigger of the drill motor to remove the burr from around the edge of the hole.
Wipe the cutting fluid from the surface of the stainless steel sheet.
Wear leather work gloves to avoid cuts while handling a stainless steel sheet. Use eye protection to protect your eyes when using a drill motor.