Choosing the flute count
Flute count is the first decision and it follows from the material rather than from the catalogue page.
Two flutes give the largest chip room, which matters in aluminium and other gummy materials where the chip must clear fast. Three flutes are the general-purpose compromise for steel and stainless. Five flutes stiffen the drill and improve hole roundness and finish in harder steels and cast iron, at the cost of chip room.
| Material | Flutes | Reason |
|---|---|---|
| Aluminium and non-ferrous | 2 | Maximum chip room, prevents packing and built-up edge |
| General and low-carbon steel | 3 | Balance of chip room and rigidity |
| Stainless steel | 3 | Firm cutting action limits work hardening at the edge |
| Hardened and alloy steel | 5 | Rigidity holds hole size and roundness |
| Cast iron | 5 | Stiffness suits short, broken chips |
| Titanium | 3 | Chip room with enough stiffness to limit heat build-up |
Depth capability and coolant
Beyond roughly three times diameter, chip evacuation becomes the limiting factor rather than the cutting edge. Deep holes need either a pecking cycle or coolant delivered through the tool, and the two are not equivalent.
Through-tool coolant pushes chips back up the flutes instead of letting them pack, which allows a single-pass operation at depths that would otherwise need retraction cycles. It also removes heat at the cutting edge where it is generated, rather than from the outside in. Our coolant-through designs run to 80 bar and are available from 5xD to 12xD.
Micro drilling
Below about 1 mm diameter the drill is fragile, runout tolerance is measured in microns, and a standard collet is frequently the source of breakage rather than the drill itself.
Micro drills demand a holder with minimal runout and a high-precision collet, a high spindle speed with controlled feed, and often a spot operation to stop the drill walking on entry. We supply micro drills from 0.5 mm together with the collets and holders that keep them running true, because supplying the drill alone usually produces a breakage that gets blamed on the tool.
Coatings for drilling
The coating is chosen for the material and the coolant condition, not for hardness alone.
- TiAlN for general steel and stainless, and the default where coolant is used
- AlTiN for harder steels, dry cutting or minimum-quantity lubrication where the edge runs hot
- AlCrN for hardened steel and high-temperature alloys, with strong oxidation resistance
- TiCN for cast iron, where a tougher and less brittle layer suits an interrupted cut
- DLC for aluminium and non-ferrous, where a low-friction surface prevents built-up edge
- Uncoated micro-grain for aluminium and composites, where a polished flute matters more than a hard layer
Frequently asked questions
What is the smallest drill you manufacture?
0.5 mm in solid carbide micro drill geometry. Below that, runout at the holder becomes the dominant cause of breakage, so we also supply matched high-precision collets and holders to keep the tool running true.
When do I need a coolant-through drill?
When the depth exceeds roughly three times the diameter. Beyond that, chip evacuation limits the operation more than the cutting edge does. Through-tool coolant pushes chips back up the flutes and allows a single pass instead of retraction cycles, and our designs run to 80 bar from 5xD to 12xD.
How many flutes should a drill have?
Two for aluminium and gummy materials to maximise chip room, three as a general-purpose choice for steel and stainless, and five for hardened steels and cast iron where rigidity and hole roundness matter more than chip clearance.
Do you make step drills and special point angles?
Yes. Step drills, subland drills, flat-bottom drills and non-standard point angles are all made to drawing. Send the hole requirement and the operation, and we will confirm the geometry before grinding.
Can you supply a drill that matches another brand's geometry?
Usually yes. Send the tool or a drawing and we will match the geometry and recommend a substrate and coating for your material. Where a dimension is unclear we will ask rather than assume, because a mis-matched point angle is not obvious until the first hole is gauged.