Professional tools for commercial or occasional use. Step drills offer a significant advantage over cone drills because they offer a positive stop when a hole reaches a certain size. HSS Titanium coated drills for maximum strength With a cone drill it is easy for it to dig in and make a hole that is too large. A set of 3 step drills / stepped cone cutters. Cuts a perfectly round hole in sheet metal. -Works perfectly on drilling holes into thin materials such as steel, copper, aluminium, plastic -For complete performance each time please ensure that the drills are well lubricated, especially when drilling aluminium. -Self-starting penetrate, no working and no pilot drill needed. 3PC SET INCLUDES THE FOLLOWING 1. SMALL STEP DRILL - 4 - 12mm in 1mm increments 2. MEDIUM STEP DRILL - 4mm - 20mm in 2mm increments 3. LARGE STEP DRILL - 4mm - 30mm in 2mm increments Double flutes make a perfectly round hole and automatically deburr as you drill. Complete in metal tin / case for easy storage and transportation.