Those screws are usually all held with loctite. they have a standard thread so thats counter clockwise to open. I have a tricity bendix aw1002w and to get mine off i had to put a torx bit in a ratchet and clamp the pully wheel with a piece of timber. the extra leverage on the ratchet really helps

Try some heat to the screw with a propane torch , or a hot air dryer, and try spraying some WD40 on the screw. it should be a normal right hand thread.
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Thanks.