Many machining shops adopt one single substrate‑coating combination for all workpiece materials including carbon steel, stainless steel and hardened steel. They suffer rapid edge chipping, heavy built‑up edge and unsatisfactory tool life. Cobalt content, grain size and coating system of cemented carbide drill shall be selected according to workpiece properties to maximize overall cutting performance.

For carbon steel and alloy‑steel, sub‑fine‑grain carbide substrate with medium cobalt content together with general‑purpose TiAlN coating is preferred. The substrate balances toughness and wear‑resistance, while coating forms protective aluminum‑oxide film against cutting heat, fit for mass‑production drilling of auto‑parts and general machinery components.

Austenitic stainless‑steel such as 304 / 316 is prone to work‑hardening. Ultra‑fine‑grain substrate with enhanced micro‑chipping resistance and low‑stress PVD coating are required. High residual‑stress coating shall be avoided for stainless‑steel, otherwise micro‑chipping occurs at cut‑in moment. Polished flute surface reduces built‑up‑edge risk; steel‑oriented drills cannot be reused directly.

For hardened‑steel over HRC45, low‑cobalt ultra‑fine / nano‑grain carbide substrate with higher base hardness and heat‑resistant AlCrN coating are recommended. Local tip temperature rises extremely high when drilling hard steel, requiring excellent hot‑hardness from coating. Edge micro‑honing is mandatory to remove grinding micro‑notches and prevent immediate chipping under cutting load.

A common procurement pitfall is judging merely by appearance and unit price. Wrong substrate‑coating combination may cut tool service‑life several times. Workpiece hardness and material category shall be clarified to decide grain size, cobalt percentage and coating solution. Small‑lot machine trial is suggested.

Kehua Cutting Technology (Wuxi) Co., Ltd. supplies multi‑series high‑performance drills (P/M/K/N/H/S grade) with differentiated substrate and coating for steel, stainless‑steel, cast‑iron, non‑ferrous metal, hardened‑steel and super‑alloy. Both standard cemented carbide drills and custom non‑standard tools are available. Supported by in‑house coating center, we serve mold, auto‑parts, wind‑power, aerospace and 3C industries. We assist customers on drill selection to optimize hole‑making processing cost.