Titanium is chosen for strength to weight, corrosion resistance and biocompatibility, and it fights every one of those properties back at the cutting edge. It conducts heat poorly so the heat stays at the tool, it work hardens, it is chemically reactive with tool materials at temperature, and it is springy enough to push away from the cut.
Why it is hard to machine
Titanium's thermal conductivity is a fraction of steel's, so heat generated at the cut has nowhere to go except into the tool. Its low modulus means it deflects under cutting force and springs back, rubbing the flank of the tool. And at high temperature it reacts with most tool materials. The combination destroys cutting edges quickly and limits how fast material can be removed.
What the process needs
Rigidity above all: short tools, tight fixtures, and a machine that does not flex. Sharp tools with the correct geometry, replaced on a schedule rather than when they fail. High pressure coolant delivered to the cutting zone, which is what actually carries heat away and evacuates chips. Constant engagement strategies that avoid dwelling, since a stationary tool in contact work hardens the surface immediately.
Cost against aluminium
Material removal rates are a small fraction of aluminium's, tooling is consumed far faster, and the material itself is expensive. On a part with a lot of material removal the difference is a large multiple, and it is why the buy to fly ratio matters so much and why titanium is the alloy where near net shape processes such as additive manufacturing make their clearest case.
Specifying titanium work
Name the alloy and condition. Say whether machining stock and a fixturing datum are provided if the blank is a forging or a casting. Discuss whether features can be redesigned to reduce material removal, since that is where the money is. And expect the shop to want more information about the part than they would for an aluminium job, which is a good sign rather than a bad one.
Questions people ask about titanium cnc machining
Why is titanium expensive to machine?
Low thermal conductivity keeps heat at the tool edge, the material work hardens and reacts with tool materials, so removal rates are low and tooling is consumed quickly.
What does a shop need to machine titanium well?
Rigidity, sharp tools replaced on schedule, high pressure coolant at the cutting zone, and toolpaths that keep engagement constant.
How does the cost compare with aluminium?
A large multiple on any part with substantial material removal, which is why near net shape routes such as forging and additive manufacturing are attractive in titanium.
Can titanium hold tight tolerances?
Yes, with a rigid setup and controlled heat. Its low modulus means it deflects under cutting force, so light finishing passes and good fixturing matter more than usual.