Buy Long Drill Bits Online in Australia
Long Drill Bit Sizes — Quick Reference
Long series and extra-long drill bits extend flute and overall length beyond the standard jobber drill — for drilling deeper holes, reaching past workholding obstruction, or accessing through thick sections. Match drill TYPE to substrate (HSS for mild steel, cobalt for stainless/tough alloys) and LENGTH to your reach requirement. AIMS stocks Sutton Tools, P&N and NACHI long-series drills.
| Drill Length Series | Overall Length (Typical) | Flute Length | Best For |
|---|---|---|---|
| Jobber (Standard) | ~12-14× drill diameter | ~9× diameter | General drilling — workshop default |
| Stub Series (Short) | ~6-8× diameter | ~4× diameter | Stiffer drill, less flex — sheet metal, light work |
| Long Series | ~17-20× diameter | ~12-14× diameter | Deeper drilling, past workholding, thicker plate |
| Extra-Long | ~24-30× diameter | ~18× diameter | Very deep holes, hard-access positions |
| Aircraft Extension | 150-300 mm long | ~80% of overall | Aviation, automotive panel work, deep-reach repair |
Important: longer drills are MORE FLEXIBLE and prone to wandering. Use a starter drill, pilot hole, or drill bushing for accurate hole position when using long drills. Run at LOWER RPM than equivalent jobber drills to compensate for vibration. For cobalt drilling on stainless/tough alloys, see cobalt drill bits. For drill bit sizing reference, see our drill bit size chart. Companion ranges: drilling, jobber drill bits.
Long Drill Bits for Deep Hole Drilling
Long series and extra-long drill bits are designed for drilling deeper than standard jobber-length drills allow — reaching through thick sections of material, drilling at depth in blind holes, or accessing drilling positions that standard-length drills cannot reach due to interference with the work surface or workholding. AIMS Industrial stocks long series HSS and cobalt drill bits from Sutton Tools, P&N, and NACHI for engineering workshops, toolrooms, and maintenance operations requiring extended drilling reach.
Long Series vs Extra-Long Drill Bits
Long series drills extend the flute length and overall length beyond the jobber series standard, providing greater reach while retaining the same shank diameter and point geometry. They are the practical choice for most extended-reach drilling applications — drilling through heavy plate, elongated tube sections, or parts where the drill needs to reach past obstruction before entering the material. Extra-long drills provide even greater extension for applications requiring significant depth, such as drilling through structural members, machine frames, or extended component lengths. As flute length increases, lateral rigidity decreases — extra-long drills require careful support, reduced feed rates, and more frequent withdrawal for chip clearing to avoid deflection and drill breakage.
Sutton Tools Long Series Drills
Sutton Tools manufactures long series HSS drills to precise dimensional standards that provide consistent diameter accuracy and surface finish over the extended flute length. Sutton's Australian manufacturing heritage and engineering commitment make their long series range a reliable production drill for workshop and toolroom applications. The M35 cobalt variant provides improved heat resistance for drilling in stainless steel and high-tensile alloys where the extended contact time of deep drilling generates significant heat at the cutting edge.
P&N and NACHI Long Drills
P&N long series drills offer competitive performance for general workshop deep drilling in mild steel, aluminium, and engineering plastics. NACHI, a Japanese manufacturer with a strong reputation in precision cutting tools, produces long series drills with tight tolerances and consistent geometry — well suited to toolroom and precision component applications where hole position accuracy over depth is important. NACHI cobalt-grade long drills are specified for demanding materials where standard HSS would lose cutting edge integrity before reaching the required depth.
Drilling Technique for Long Bits
Successful deep drilling with long series bits requires attention to several factors: correct starting speed for the material and drill diameter, adequate coolant or cutting fluid delivery to the drill tip, frequent withdrawal to clear chips before they compact in the flute and cause breakage, and proper workholding to prevent component movement that would side-load the drill. For drill selection by material type, size, and depth requirements, or for bulk supply pricing, contact our team at AIMS Industrial.
People Also Ask — Long Drill Bits
Q: When do I need a long-series drill bit vs a standard jobber?
Long-series drill bits are used when standard jobber length can't reach the work — deep blind holes, drilling through structural members, plumbing and electrical access work, or any application where the chuck or quill can't sit close to the work surface. They sacrifice rigidity for reach, so they need slower speeds and lighter feed pressure to avoid wandering or breakage.
Q: What lengths are available in long-series drills?
Common long-series lengths range from 200mm to 600mm in 6mm to 13mm diameters. For specialised work (plumbing, sprinkler installation, deep pocket drilling) extra-long versions go to 900mm and beyond. As length increases, achievable straightness and surface finish reduce — for accuracy-critical work, use the shortest drill bit that reaches the depth needed.
Q: Why does a long drill bit wander off centre?
Long drills have less torsional and bending stiffness than shorter bits, so any side load on the cutting tip walks the drill off-line. Common causes: starting the hole without a pilot indent (centre punch or pilot drill), feeding too aggressively, dull cutting edges, or the workpiece flexing under feed pressure. Pilot the hole first with a short drill, then complete with the long-series; this is the standard technique for accurate deep holes.
Q: What speed should I run a long drill bit at?
Slower than the equivalent jobber length — typically 50-70 percent of the speed you'd use for the same diameter short drill. The slower speed gives the cutting edges time to clear chips without overheating, and reduces the deflection that causes wandering. Steady feed pressure is more important than RPM for long drills; let the bit cut at its own pace rather than forcing depth.
Q: Should I use cutting fluid with long drill bits?
Yes, where the material requires it. Long bits run hotter than jobber drills because chips take longer to evacuate up the flutes — fluid helps cooling and chip evacuation simultaneously. For mild steel and stainless, soluble cutting oil works well. For aluminium use kerosene or a dedicated aluminium tap fluid; for cast iron run dry. Periodically withdraw the drill to clear chips on deep holes — drilling continuously without retraction packs the flutes.
Q: Should I use a pilot hole with a long-series drill?
Yes for accurate hole location. Start with a spot drill or centre drill to establish the hole centre and provide a small conical seat for the long drill point to enter without wandering. Then use a smaller-diameter pilot drill (typically 30-50 percent of the final hole diameter) to create a guide hole for the long drill to follow. Finally use the long-series drill to open the hole to final size — the pilot hole guides the drill point and reduces bending loads on the long drill body. For deep holes where hole straightness matters, this three-step approach gives better accuracy than a single long-drill pass.
Q: HSS or HSS-Co for long drill bits?
HSS (M2) suits most workshop use in mild steel, aluminium, brass, plastics, and general non-abrasive materials. Cost-effective and readily available in long-series sizes. HSS-Co (typically M35 with 5 percent cobalt, or M42 with 8 percent cobalt) suits stainless steel, hardened stock (up to 40 HRC), high-strength alloys, and long-run production where tool life matters. Cobalt HSS runs hotter without losing hardness — critical for stainless where poor heat resistance causes work hardening and drill failure. For occasional long-hole drilling in mild steel, HSS is fine. For regular stainless work or difficult materials, invest in cobalt HSS long drills. Read our cobalt drill bit guide for detail.
Q: What is the difference between long-series drills and aircraft extension drills?
Long-series drills have long cutting flutes (typically 12-20 times the drill diameter) — the entire drill body from tip to shank is fluted. Suits deep-hole drilling where chip evacuation from the full hole depth matters. Aircraft extension drills have normal cutting flute length (jobber length) but a very long shank between the flutes and the drill chuck — usually 300-600mm+. Suits reaching past obstructions and fixturing to drill a hole at normal cutting depth in the workpiece, rather than drilling deep holes. Choose long-series for deep-hole drilling; aircraft extensions for long-reach access to a normal-depth hole.
Q: Should I use a drill press for long drill bits?
Yes, strongly preferred for accuracy and safety. Long drill bits deflect easily under lateral load — hand-holding a drill machine while pressing on a long drill bit deflects the drill and produces oversize, off-centre holes. Long drills also whip more violently if they catch or bind, and a hand-held drill offers no protection against a whipping bit. A drill press provides rigid mounting, controlled feed, and a fixed spindle axis — much safer and much more accurate for long-drill work. For portable applications where a drill press isn't available, use a drill guide, magnetic base drill, or angle drill with proper support to constrain the drill.
Q: Which brands does AIMS stock for long drill bits?
AIMS stocks long-series drill bits from Sutton Tools (Australian-made — full range in HSS and cobalt HSS across common diameters and lengths) and Bordo (Australian-owned — competitive workshop range across HSS and cobalt). See the Sutton Tools range for the full Australian-made cutting tool catalogue and Bordo for the Bordo alternative. Also see drill bits for the wider drill bit range including standard jobber-length drills. For selection detail read our drill bit selection guide and drill bit types guide.