Hi Nick,
Not that I drill a lot of holes in aluminium, but I figured I would still contribute a few ideas.
- What does your toolpath look like ? I like helical ramping down to max depth + one or two passes at full depth around the perimeter. You could try ramping in at a low(er) helix angle?
- Consider using an air blast and/or a little lubrication ?
- the 10-15min you mention, does that that mean you cut a number of holes correctly, and then at some point cutting the next hole goes wrong ? Have you been able to tell whether the tool break happens when the tool is at the max cutting depth ?
- I assume you tried reducing stickout to the absolute minimum ?
- have you checked runout ? it may be low enough that it kinda works, but high enough that it introduces enough extra forces/vibration on the cutter that it wears out quickly, and after 15minutes of wear it decides to call it quits ? How does the cut sound?