About High Speed Steel(HSS)
HSS-4241:
Suitable for workpieces with hardness below 25HRC, such as iron plate, aluminum plate, PVC plate.
HSS-6542:
Suitable for workpieces with hardness below 28HRC, such as iron plate, aluminum plate, metal sheet and copper plate.
HSS-CO/M35:
Suitable for workpieces less than 5mm thickness, such as iron plate, aluminum plate, metal sheet, or workpieces less than 1mm thickness of stainless steel.
Note: While drilling on 304 stainless steel, thickness under 1mm you can use a hand drill with power above 800W, thickness between 2-3mm will require a bench drill with speed below 500 rpm.