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.