.050-.060 is preferred safe clearance. Always do the counterweights when you can, much better way. ( all depends on bob weights too)Also, if you just go all crazy with a die grinder and dont do a good job of working that down, and smoothing it all, every one of those marks is a potential stress riser, aiding to a crack down the road.If you can see a sand mark, or heavy gouge, its a stress riser.