400 mm Overall Length: Coolant-Through Solid Carbide Drills

Most catalogue coolant-through drills stop at modest overall lengths: the longer the body, the harder it is to keep a concentric coolant bore, control flute runout, and maintain seal surfaces for the collet or adapter. At 400 mm overall length, those tolerances compound — the tool is no longer a “long drill” in name only; it is a precision shaft that must also carry high-pressure coolant end-to-end.

This case documents our solid carbide coolant-through drills produced at 400 mm overall length (customer-specific diameters and point styles apply). The design goal is simple to state and difficult to manufacture: keep the internal coolant path aligned with the external axis so coolant reaches the lip under pressure, evacuate chips in deep holes, and avoid the leaks and chatter that appear when straightness drifts over hundreds of millimetres.

Manufacturing combines controlled blank preparation, deep-hole processing of the coolant bore, precision flute and point grinding, and full-length runout checks. We verify sealing faces and pressure behaviour so the tool matches real machine conditions — not only a drawing dimension.

We are candid about market reality: only a handful of manufacturers worldwide can ship repeatable coolant-through solid carbide drills at this overall length with predictable life. If your application needs deep reach with through-tool coolant — mould bases, energy equipment, large structural steel, or other long-stack drilling — send diameter, overall length, material, and coolant pressure. Our applications team will confirm feasibility and lead time from Changzhou.