I'm ready to buy an angle grinder. My first use will be to "dress" a blacksmith anvil by grinding the face flat and square with a flapper wheel and also rounding some sharp edges. But I want a versatile tool. (I foresee cutting pipe, trimming concrete edges, possibly sharpening mower blades, and lots more once I get more familiar with it.) I generally prefer to invest in good tools that last, rather than saving cash initially but replacing soon after. So, when shopping for a decent quality corded angle-grinder with some versatility, how important is variable speed? For which uses?
Variable speed will be used if you want to use the angle grinder as a polisher/buffer, as those wheels wont work as well at 10,000rpm.
When shopping for an angle-grinder, how important is variable speed?
The importance is use dependent. I think that using different disks (grinding, sanding, cutting, brushing, etc.) is a satisfactory way to get the most use from the grinder. I've never had any desire for a grinder that would go a different speed. Actually, I think that controlling the grinder is probably easiest at top speed.
For which uses?
Generally a grinder is used for working with steel, in which case one speed is fine (that's what I have- no complaints). I have also used it for sanding patches of concrete; dust is a little problem, if/when it gets in the motor (maybe it should be wrapped with a rag-filter- but don't let the rag get caught in the wheel, or else). I suppose that if you are an artist or you're using a grinder for high precision, or on delicate or soft material, I could understand wanting the grinder to go more slowly, but then again, maybe not.