Large volumes of coolant through spindle and tool can help overcome the demands of titanium machining.

Titanium as a work piece material is finding its way into most machine shops with milling being the dominant machining method particularly in structural parts. Material removal rate is becoming an increasingly competitive factor for jobs but is not as easy to achieve in this material having challenging machinability. But new tool and process developments are providing this increasingly useful design material with new possibilities to improve machining costs.

Why has titanium got challenging machinability?
The physical, chemical and thermal properties of titanium make it a uniquely demanding material to machine. There are a number of titanium alloys with different properties and machinability varies considerably – from the traditional Ti6Al4V to stronger alloys like Ti10-2-3 and now Ti5553.

The main characteristics are:
• Risk of tool wear due to the cutting edge being exposed to higher temperatures and having to absorb more heat as titanium is a poor conductor of heat and more heat is generated in machining titanium
• Tool wear/breakdown due to the smearing tendency of titanium, which is reactive with tool materials and where the chip welds to the insert, causing edge-line frittering when re-entering the cut
• Material deflection/chatter tendency due to the elasticity of titanium
• Risk of rapid tool wear because of the localized high pressure in combination with heat at the small contact surface

There are a few general rules for machining titanium to help in overcoming these demands:
• Use relatively low cutting speeds
• Use sharp cutting edges
• Optimize feed rates and avoid idling while in cut
• Use large volumes of coolant, preferably at high pressure through spindle and tool
• Replace cutting edges at first sign of any wear
• Employ climb (down) milling wherever possible

CLICK HERE to read more about milling developments…
- For machining any of the titanium alloys.
- An indexable insert, long-edge cutter.
- When the application involves narrow cavities.
- When face milling titanium.

Article originally published on Tooling & Production 2.2011.

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