Deep Hole Drilling Titanium and Titanium Alloys

Titanium alloys are among the most difficult materials for deep hole drilling. Their low thermal conductivity (heat stays in the tool), chemical reactivity (welds to carbide), and low modulus of elasticity (springback) create a unique combination of challenges.

This guide covers deep hole drilling parameters, tooling, and best practices for titanium alloys, primarily Ti-6Al-4V (Grade 5).

Titanium Material Properties

Property	Titanium (Ti-6Al-4V)	Comparison to Steel
Thermal conductivity	7 W/m·K	5–7× lower than steel
Modulus of elasticity	114 GPa	~50% of steel
Hardness	30–36 HRC	Similar to medium-carbon steel
Tensile strength	900–1,100 MPa	Higher than most steels
Chemical reactivity	High — reacts with carbide at cutting temperatures	Significantly more reactive

Why Titanium Is Difficult for Deep Hole Drilling

Heat concentration — Titanium’s low thermal conductivity means nearly all cutting heat goes into the tool, not the chip. The cutting edge experiences temperatures 2–3× higher than when cutting steel at the same speed.
Chemical reactivity — At the high temperatures generated during deep hole drilling, titanium chemically reacts with the cobalt binder in carbide tools, causing rapid crater wear.
Springback — Titanium’s low modulus means the bore wall springs back after the guide pads pass, changing the effective interference. This can cause the pads to rub excessively.
Serrated chip formation — Titanium produces thin, serrated chips that can be difficult to evacuate reliably.
Work hardening — If the tool dwells, the surface work-hardens rapidly, making subsequent cutting more difficult.

Cutting Parameters

Gun Drilling — Ti-6Al-4V

Diameter	Speed (m/min)	Feed (mm/rev)	Coolant Pressure (bar)
3–6 mm	15–22	0.006–0.012	100–140
6–12 mm	18–25	0.010–0.020	70–100
12–20 mm	18–25	0.015–0.025	50–70
20–30 mm	15–22	0.020–0.035	40–60

BTA Drilling — Ti-6Al-4V

Diameter	Speed (m/min)	Feed (mm/rev)	Coolant Pressure (bar)
20–40 mm	18–25	0.08–0.15	40–60
40–65 mm	15–22	0.12–0.20	35–50
65–100 mm	15–20	0.15–0.25	30–45

Depth Ratio Adjustments for Titanium

Titanium requires more aggressive depth ratio adjustments than steel:

Depth Ratio	Speed Reduction	Feed Reduction	Coolant Increase
< 20:1	None	None	None
20:1–40:1	10%	10%	10%
40:1–60:1	20%	15%	20%
60:1–80:1	30%	25%	30%
> 80:1	40%	35%	40%

Tool Selection

Carbide Grade

Recommendation	Grade	Why
Best	Ultra-fine grain (0.2–0.5 µm), 8–10% Co	Combines wear resistance with toughness
Acceptable	Fine grain (0.5–1 µm), 8–12% Co	Good for moderate production

Coating

Coating	Performance	Why
AlTiN nano	Excellent	Highest heat resistance (up to 1,100°C)
TiAlN	Good	Standard for moderate speeds
Uncoated	Not recommended	Chemical reactivity too high

Tool Geometry

Feature	Recommended	Why
Nose grind	N-8 or facet grind with sharp edge	Sharp edge reduces cutting forces
Edge preparation	Sharp (no chamfer or hone)	Any edge hone increases cutting forces
Flute surface	Polished	Reduces chip friction in the flute
Guide pad interference	Reduce by 10–20% vs. steel	Compensates for titanium’s springback

Coolant Strategy

Parameter	Recommended	Why
Coolant type	Neat oil with EP additives	Maximum lubricity and heat removal
Coolant pressure	30–50% above standard for diameter	Must overcome heat concentration
Coolant volume	Maximum available	Heat management is critical
Coolant temperature	25–35°C (cooler than steel)	Lower temperature keeps tool cool
Filtration	10 micron or better	Clean coolant is essential for tool life

Chip Shape Expectations

Titanium chips are typically thin and serrated — this is normal. Do not expect the short C-shaped chips typical of steel.

Chip Appearance	What It Means
Thin, serrated chips	Normal for titanium
Long, continuous chips	Feed too low — increase 10%
Blue/burned chips	Speed too high or coolant insufficient
Powdered chips	Feed too high or tool dull

Common Problems

Problem	Cause	Solution
Rapid tool wear / short tool life	Heat concentration and chemical reactivity	Reduce speed 10–15%; switch to AlTiN coating
Built-up edge	Titanium welding to carbide	Increase speed if BUE is from cold welding; decrease if from high temperature
Oversize hole	Springback — bore contracts after pads pass	Reduce guide pad interference 10–20%
Chatter	Low modulus causes vibration	Increase feed; reduce speed; add whip guide
Poor surface finish	Springback causing pad rubbing	Reduce pad interference; check coolant lubricity
Tool breakage at depth	Heat buildup weakens the cutting edge	Increase coolant pressure; reduce depth ratio
Chip packing	Thin, serrated chips pack in flute	Increase feed; check coolant flow

Summary

Titanium deep hole drilling is characterized by heat management and chemical reactivity challenges. Use low cutting speeds (15–25 m/min), moderate feeds, maximum coolant pressure and flow, and AlTiN-coated carbide tools. Reduce guide pad interference to compensate for springback. Accept shorter tool life than in steel — 300–500 linear inches between regrinds is normal. Never let the tool dwell in the cut; the material work-hardens nearly instantly.

For troubleshooting, see deep hole drilling troubleshooting. For tool materials, see cutting tool materials guide. For a complete overview, visit the materials-specific drilling guide.