Spotting Drill Bit Sets

Spotting Drill Bit Sets for Australian Toolroom and Production Drilling

Spotting drill bits (also called spot drills or starter drills) are short, stiff drill bits with a wide-angle point that produces a precise centre mark on the workpiece — providing the starting point for accurate drilling with longer twist drills. For Australian toolroom, machining, and production work where hole position accuracy matters, spotting first and then drilling produces holes that twist drills alone can't match for centring accuracy. AIMS Industrial supplies spotting drill bits and centre drills for trade and industrial customers.

Why spot before drilling

Standard twist drills, particularly in larger sizes, tend to wander as they start cutting — the chisel edge skates across the work surface before catching, producing holes that are slightly off the intended position. A spotting drill, with its short rigid body and wide-angle point, doesn't wander — it produces a precise cone-shaped indent at the exact intended position. The subsequent twist drill follows this cone reliably, producing accurately-positioned holes.

The bit types we stock

• Standard spotting drills — short HSS bits with wide-angle points (typically 90°, 120°, or 142°)
• Carbide spotting drills — for harder materials and production work where HSS spotting drills wear too fast
• Combined drill and countersink (centre drills) — Type A, B, and R combinations that drill a small hole and countersink in one operation; standard for lathe centre work
• NC (Numerical Control) spotting drills — purpose-engineered for CNC machining centre use
• Spotting drill sets — multiple sizes in a hard case for varied work

Point angles — match to follow-up drill

• 90° point — produces a wider, flatter spot; suits larger twist drills (typical 118° or 135° points)
• 120° point — general-purpose intermediate angle
• 142° point — narrower point; suits smaller twist drills and holes where minimal spotting depth is needed

The general rule: spotting drill point angle should be slightly wider than the following twist drill's point angle. This ensures the twist drill's lips engage the spotted cone simultaneously, preventing wandering during the start of the main drill operation.

Where spotting drills earn their place

• CNC machining centres — accurate hole positioning across multi-axis drilling sequences
• Toolroom and precision work — where hole position tolerance is tighter than what twist drills alone deliver
• Drill press accuracy — where the drill press's dial-and-table positioning must translate to accurate hole positions
• Multiple identical holes — production drilling of repeated patterns where consistent positioning matters
• Bolted joint manufacture — where multiple holes must align between mating parts

Centre drills for lathe work

Centre drills (combined drill-and-countersink, also called Slocombe drills) drill a small pilot hole and a 60° countersink in a single operation — producing the centre mark that supports a lathe centre during turning. Type A is the most common (no protecting chamfer). Type B has a protecting chamfer to prevent damage during work. Type R is the bell-mouth variation. For workshops doing lathe work, a centre drill set is essential equipment.

Sizing

Spotting drills come in metric sizes from 3mm through 25mm and imperial equivalents. Centre drills are sized by number (#0 through #8 typically) corresponding to specific drill diameter and overall size combinations. Match drill size to the work and the centre size required.

Brands stocked at AIMS

Sutton Tools, Bordo, and Champion cover the spotting drill range in HSS. Carbide spotting drills are stocked for production applications. For specialty NC spotting drills or specific point angles, sourcing through our distribution channels covers most options.

Drilling practice

Run spotting drills at higher RPM than twist drills (the short rigid body tolerates higher speeds). Apply firm pressure briefly — the spotting cycle is fast, typically 1-2 seconds. Withdraw the bit cleanly to leave a clean cone. The depth of the spot should be enough to start the following twist drill but not deeper than necessary — over-deep spots waste tool life and slow the operation.

Companion ranges at AIMS

Spotting drill bit sets sit alongside our broader cutting tool range — see spade drill bit sets, multi-purpose drill bits, reduced shank drill bits, and reamer sets for the related products.

Need help speccing spotting drills for CNC, toolroom, or production work? contact our team — we'll match by size, point angle, and material grade.