Drill bit "catching" and jumping out the hole

[commathe]

I am not sure what is causing this. I drilled a 3mm pilot hole for my unibit (which starts at 4) but the unibit doesn't get much further than half a millimetre in before it catches and jumps out. I am not using a drill press, I am doing it by hand. I was told that the drill bit was suitable for aluminium but I am now worrying that it is too soft seeing as another bit manged to make 5 successful holes in the same enclosure. Am I right? What might be causing this?

[oldrenegade]

Aluminium can 'cold weld' itself to the drill bit. Try some oil on there.

[tonyharker]

Paraffin (Kerosene) is a good lubricant for Aluminium (Aluminum).