Reduced Shank Drill Bits

Reduced Shank Drill Bits

Reduced shank drill bits have a cutting flute diameter larger than the shank diameter — typically a 1/2 inch shank with cutting diameters from about 13mm up to 32mm or larger. The reduced shank lets you drill larger holes with a standard 1/2 inch chuck drill press or hand drill, instead of needing a larger chuck or a Morse taper drill. AIMS Industrial stocks reduced shank drill bits for trade and industrial use where larger-diameter drilling is needed without specialist drilling equipment.

The standard shank sizes

• 1/2 inch (13mm) shank — fits the standard 1/2 inch chuck on most drill presses and heavy-duty hand drills
• 3/8 inch (10mm) shank — for smaller drilling equipment with 3/8 inch chucks
• 5/8 inch shank — for heavier-duty drill presses with larger chucks

Where reduced shank earns its place

• Large-hole drilling without specialist equipment — drilling 16mm-32mm holes without owning a Morse taper drill press
• Service van and site work — large-diameter drills that fit standard portable drills
• Workshop convenience — keeping a large-diameter drill range without needing dedicated equipment
• Magnetic base drill use — many magnetic drills use 1/2 inch chuck mounting for jobber-style drills

Sizes typically stocked

Reduced shank drill bits are stocked in metric sizes from approximately 13.5mm to 30mm, and imperial sizes from approximately 9/16 inch to 1-1/4 inch. Sizes that are commonly drilled are stocked as singles; sets covering the larger metric or imperial range are also available.

HSS versus other materials

Reduced shank drill bits are typically HSS (high-speed steel) for general workshop use, with HSS-E (cobalt) available for tougher materials and stainless steel applications. Surface coatings (TiN, TiCN) extend tool life in production drilling. For specific harder materials or production use, ask about coated or carbide-tipped reduced shank options.

Drilling practice

Larger drill diameters demand slower spindle speeds — running too fast causes heat build-up that destroys the cutting edge and the workpiece. As a rough guide, halve the spindle speed when going from 12mm to 25mm drill diameter. Use cutting fluid (Tap Magic, Molycut, or a flood coolant for production work), apply firm steady pressure, and let the drill cut at its natural feed rate. Pecking (drill, retract, drill again) helps clear chips on deeper holes. For larger drills (over 20mm), use a pilot hole drilled with a smaller bit first — the larger drill follows the pilot, reducing the chance of grabbing in thin material or wandering off centre.

Brands stocked at AIMS

Sutton Tools, Bordo, and Champion cover the reduced shank drill bit range in HSS, with HSS-E available for tougher applications. For specific brand requirements or larger sizes, contact our team for sourcing through our distribution channels.

Companion ranges

Reduced shank drill bits sit alongside our broader drill bit range — jobber drills (HSS, HSS-E, carbide), step drills, hole saws, and annular cutters. For complete drilling kits or larger-diameter work where annular cutters might be more efficient, contact our team to discuss the application.