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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?

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    I'm sorry to say that an angle grinder really is not the proper tool to resurface an anvil. A good machine shop with a surface grinder should be able to grind the top perfectly flat. An angle grinder will more or less just follow the existing contours instead of flattening it out. Many old anvils also have lost their temper. When you strike it with a hammer, the hammer should bounce and there should also be a distinctive ringing noise. If there is a thud, then you have what is called a dead anvil. If that is the case, then you would need to have it case hardened to restore it.
    – Jason Hutchinson
    May 18, 2016 at 20:27
  • Thanks Jason. Your point is well taken about anvil flatness and hardness, but I was asking about grinders. Machining is fine, but Angle grinders are also used to restore the radius of corners and to smooth out uneven wear. Lots of examples with good results online.
    – jbbenni
    May 18, 2016 at 21:25

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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.

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    Commonly buffers run at 1700-1800 rpm... that's about 5 times slower than a grinder. At 4000 rpms, I'd expect sparks to start flying. Variable speed grinder or a separate tool? For a two speed tool (made for buffing or grinding) I'd want to be sure that I could dail in the rpms or that I only had two pre-set speeds. Otherwise it might be a mistake waiting to happen (unless the car already needs a paint job). Like a corvette engine on a scooter.
    – Ben Welborn
    May 19, 2016 at 16:35
  • There is good info in multiple answers, but this one most directly answers the question I asked. Thanks to all the contributors!
    – jbbenni
    May 19, 2016 at 20:52
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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.

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  • I think you're basically saying versatility comes from changing disks, and that variable speed isn't required - except (possibly) for unusual circumstances, and maybe not even then. Unless others credibly refute that view, then it answers my question. Thanks!
    – jbbenni
    May 18, 2016 at 21:36

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