I was tempted to do this, but wanted to check if I am being daft…
There is a threaded hole on top of the spindle mount (indicated in the attached photo).
Do you think I could screw a custom mount onto that and hold an iPhone at an angle there so I can record footage of the machine in action from the point of view of the spindle?
You should be able to! I have seen that hole used to mount coolant and air tubes. Id be worried about vibration giving your shutter and focus weird problems, so you will want to try and use nylon bolts and rubber dampeners/isolators. And keep in mind the spindle does retract over on X pretty far from the table center. So. You’ll always see the tool. Not always the part. Id personally look at mounting on the top of Y.
@vectronic that hole can be used to mount accessories. Doing so will not cause any issues with the machine so have at it!
Happy machining (and filming )!