Stub Drill Bits

Stub Drill Bits

Stub drill bits — also called screw machine length drills — are a shorter version of the standard jobber drill, with a reduced flute length and overall length compared to DIN338 jobber geometry. The shorter, stiffer design reduces deflection and runout, making stub drills the preferred choice for CNC drilling, tight-tolerance work and applications where hole position accuracy is critical.

Sutton Tools and Bordo

AIMS stocks stub drill bits from Sutton Tools and Bordo. Sutton's D186 Blue Bullet stub series uses premium HSS in the standard DIN1897 geometry — a practical choice for general-purpose CNC drilling in mild steel, cast iron and aluminium. The D151 and D177 CNC stub series are made from cobalt steel (HSSE) with TiAlN coating, designed for stainless steel, titanium and high-tensile alloys in production CNC environments. Sutton's D153 Black Magic stub series adds a R40 VA geometry with cobalt TiAlN — optimised for stainless and austenitic steels where work hardening is a concern. Bordo supplies cobalt TiAlN-coated stub drills as an alternative option for hard-material drilling.

DIN1897 — The Short-Flute Standard

DIN1897 defines the short-flute (stub) drill standard — shorter overall and shorter fluted section than the DIN338 jobber standard. The reduced length means a stiffer drill with less tendency to wander on entry and deflect during cut, which is particularly important in CNC applications where hole position tolerances are tight and drilling is done without centre-punch guidance.

TiAlN Coating

TiAlN (titanium aluminium nitride) coating increases hardness and oxidation resistance, enabling higher cutting speeds and extending tool life in demanding materials. In cobalt stub drills, TiAlN is the standard coating for stainless, cast iron, hard aluminium alloys and other materials that cause rapid uncoated drill wear.

When to Use Stub vs Jobber Length

Use stub drills in CNC machining centres for position-critical drilling, in short-grip toolholders with limited spindle clearance, and for drilling hard or work-hardening materials where a stiffer drill improves performance. Jobber-length drills remain the standard choice for general bench drilling, hand drilling and deep-hole work where the extra flute length is needed for chip clearance.