Trouble with motors in this hp range is that the cheapest to manufacture is 3600 rpm, so that's what most are. (except for Derek who has 50 cycle power so 3000 rpm). Variable speed can help but the turndown is only effective to around 2500 rpm. You want one that runs at 1800 rpm or if bigger than 10" you may find a 900 rpm machine. Variable speed from there would be an excellent find.