"GTFO my bandz" or something more mature yet along those lines.
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If I had sex as much as you said the word "shit" I would be paris hilton.

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I have never felt closer to either cheese or weasels

Quote by Vermintide

Ummm, I wouldn't...

Are you really so concerned with the quality of the musicians?

I would choose a mate I'd played with for years over a more skilled drummer, just because he's a mate.

Unless your drummer is really really bad, or a prick. Then its ok.
Now 100% humour free, in accordance with the rules.

Quote by ohshait
dont kick him out, just form a new band with the other drummer

that's a good way to do it. or just tell him the straightforward truth
drive him deep into the forest open the door and say "your free!" ...... or just sit him down tell him why your unsatisfied with his playing and if he gets mad blame it on your bass player...
Tell him your band would like to get more serious, and if he'll work to get better keep him. If he says no, then get the new drummer.
make another band with all the members of your original band except the durmmer and get the new one
Who Said Anything About A Signature ? ಠ_ಠ
Explain to him that you want him out of the band through expressive dance.