Deep Hole Drilling Aluminum and Non-Ferrous Metals

Aluminum, brass, copper, and bronze are generally the easiest materials for deep hole drilling — they offer good machinability, predictable chip formation, and moderate tool wear. However, they have unique challenges: built-up edge (aluminum), chip control (soft, ductile chips), and the need for specialized coatings.

This guide covers deep hole drilling parameters, tooling, and best practices for non-ferrous metals.

Aluminum Alloys

Material Considerations

Alloy Series	Characteristics	Deep Hole Drilling
1xxx, 3xxx (pure, Mn)	Very soft, gummy	Difficult — built-up edge, oversize holes
5xxx (Mg)	Moderate strength	Good — standard parameters
6xxx (Mg-Si)	Good all-round (6061 is standard)	Excellent — best aluminum for deep hole drilling
7xxx (Zn)	High strength (7075)	Moderate — higher cutting forces, galling

Key Challenges

Built-up edge (BUE) — Aluminum welds to the carbide cutting edge at moderate temperatures. BUE causes oversize holes and poor surface finish.
Softness — Soft aluminum can “push” rather than cut, producing oversize holes.
Chip control — Aluminum produces long, stringy chips that are difficult to evacuate.
Galling — Aluminum deposits on guide pads, causing friction and surface damage.

Cutting Parameters — Gun Drilling

Diameter	Speed (m/min)	Feed (mm/rev)	Coolant Pressure
3–6 mm	80–150	0.010–0.080	20–35 bar
6–12 mm	100–160	0.025–0.175	20–35 bar
12–20 mm	100–160	0.040–0.200	15–30 bar
20–30 mm	80–150	0.050–0.250	15–25 bar

Cutting Parameters — BTA Drilling (Aluminum)

Diameter	Speed (m/min)	Feed (mm/rev)
20–40 mm	100–200	0.20–0.50
40–65 mm	100–180	0.25–0.60
65–100 mm	80–160	0.30–0.80

Tool Selection for Aluminum

Feature	Recommended	Why
Coating	DLC (best) or uncoated	DLC prevents BUE; uncoated works with sufficient coolant
Nose grind	N-4 (R4 relief)	Wider angle for soft materials
Flute surface	Polished	Reduces aluminum adhesion to the flute
Carbide grade	K10–K15 (3–5% Co)	Coarse grain — less chemical affinity
Guide pads	Coated (DLC) or uncoated	Prevents galling on pad surfaces

Coolant for Aluminum

Parameter	Recommendation
Coolant type	Emulsion at 8–12% (for multi-machine) or neat oil (dedicated)
Coolant pressure	Lower than steel — 15–35 bar
Filtration	20–40 micron (aluminum chips are larger)
Temperature	30–40°C

Brass and Bronze

Material Considerations

Material	Machinability	Challenges
Free-machining brass (C360)	Excellent	Minimal challenges
Naval brass	Good	Moderate tool wear
Phosphor bronze	Moderate	Abrasive — increased tool wear

Cutting Parameters — Gun Drilling

Material	Speed (m/min)	Feed (mm/rev, Ø12 mm)	Coolant
Free-machining brass	80–150	0.020–0.140	Low pressure
Naval brass	60–120	0.020–0.100	Standard
Phosphor bronze	40–80	0.015–0.060	Standard

Copper

Challenges

Challenge	Why	Solution
High ductility	Copper produces very stringy chips	High feed rate; aggressive chip breaker
Soft/gummy	BUE and oversize holes	DLC coating; lower coolant temperature
High thermal conductivity	Heat dissipates quickly	Less temperature concern than other materials

Cutting Parameters — Gun Drilling

Diameter	Speed (m/min)	Feed (mm/rev)
3–12 mm	40–70	0.010–0.040
12–25 mm	40–65	0.020–0.060

Common Problems — Non-Ferrous

Problem	Cause	Solution
Built-up edge (aluminum)	Aluminum welds to carbide	Use DLC coating; increase speed slightly
Oversize hole (aluminum)	Material pushes rather than cutting	Reduce feed; ensure tool is sharp
Long stringy chips	Feed too low for ductile material	Increase feed; use aggressive chip breaker
Galling on guide pads	Aluminum deposits on pads	Use coated pads; increase coolant lubricity
Poor surface finish	BUE on edge or galling on pads	Check coating; increase speed; DLC pads
Tool wandering in soft material	Material too soft for standard parameters	Reduce feed; increase speed

Summary

Aluminum and non-ferrous metals are generally easier to deep hole drill than steel, but they have unique failure modes — primarily BUE, galling, and oversize holes. Use DLC-coated tools for aluminum to prevent material adhesion. Run higher feed rates than steel to produce thicker chips that break more easily. Coolant pressure can be lower than for steel (15–35 bar). For extremely soft or gummy materials, keep tools very sharp and replace at the first sign of edge breakdown.

For coating details, see gun drill coatings guide. For tool materials, see cutting tool materials guide. For a complete overview, visit the materials-specific drilling guide.