Ok Garry,
Given I!m stuck wth the machin that I have, only option the is a chage of pulley,s ?

Suggestion ?

You don't need to change the pulleys. My mill goes to 3,000 rpm and it's fine. OK, not 'high speed', but it makes plenty of chips. Try air blast with puffs of kero mist for aluminium - works for me.

Cheers
Roger

Try Climb Milling and mist with kero/oil mix. In the old days we used lard and kerosene for machining Aluminium. The climb milling gets rid of the chip and the rubbing action of conventional milling, however you need to eliminate as much as possible the backlash.

I use 3 parts kero to 1 part olive oil. Brief puffs iof mist. Parts come out dry. NO harm to your skin from the oil either.
Yeah, climb milling always.

Cheers
Roger