Feature: 1. The aperture scale is clear, and it should be smaller than the ordinary twist drill. It can open a beautiful aperture without using a center punch. 2. Deburring, chamfering, rounding and reaming, functions that can not be done with twist drills can also be completed. 3. Ladder structure, widely used, a drill can open a variety of sizes and apertures 4. Suitable for workpieces with hardness below 25° such as iron plate, aluminum plate, PV plate and insulation plate 5. Using high-quality materials, strong and durable, has a long service life Specification: Item Type: Step Drill Set.Material: High-speed steel 4241 (Ti coating) Series: Inch Step Drill Specification: 1/4-1-3/8, 3/16-7/8, 3/16-1/2, 1/8-1/2, 1/4-3/4 (Unit: Inch) 5pcs set Applicable Places: Suitable for workpieces with hardness below 25° such as iron plates, aluminum plates, PV plates, and insulating plates. Package List: 5 x Step Drill Note: Customers who choose 4241 must pay attention to water cooling when hitting the steel plate. The drill bit is easy to anneal due to high temperature and smoke during use. For those who insist on this operation, the drill bit will soon be scrapped.