Best method for drilling hole for tube socket

[seedlings]

Spade bit will not leave a jagged hole... at least it hasn't for me- barely needs deburring.  Clamp and go fairly slow until you get the hang of it, but I just hold the pedal (or chassis) with my non-drilling hand and use a cordless drill.

CHAD

[Paul Marossy]

I've had good results using a regular wood spade bit on aluminum. I've even used them on a steel chassis once, just had to go slow and easy. More de-burring to do than with alumimum, though...