Posted by andrew lyner on 29/06/2020 23:59:23:
I religiously stand to one side when I turn on my bench grinder and I see other people do the same on YouTube. I wonder how dangerous those things actually are, though.
I only heard of one specific case of a grinding wheel exploding and it was pretty horrific. A relative of mine had to rebuild a guys face – which was seriously damaged.
I am always pretty careful about using my wheel and would never hit is or push hard against it but what about the issue of using the side? The drill sharpening jig I bought seems to work only when mounted so as to tough the side of the wheel so what about the 'only on the front ' mantra that you seem to hear pretty regularly.
A higher apparent risk is with angle grinder discs which have various words of warning on them. But, on YouTube again, you see all sorts of antics used by some of the DIY 'performers'.
I never actually had a proper course on grinding and I know they are given to all professional too users. Is the risk real or is it just the fear of litigation that makes managers so careful about grinding? I am at least as careful as the next man (not the one with only one eye).
Bench/surface grinder wheels are safe enough so long as you take precautions when handling and mounting. Ring test, blotters, dressing etc. If they run out of true or over-speed then you increase the risk of bursting them so always observe the printed rpm limit. standing to one side is good practice but I only do it religiously after mounting a new wheel – just in case I cracked it when clamping.
You're unlikely to overload your bench grinder to the point of stressing the wheel. Your typical 6-8" bench grinder is what 250-330 watts? A surface grinder with a 8" wheel will be 0,75kw – three times as powerful – and they slow down on heavy cuts. You would have stalled the bench grinder by the time the surface grinder had slowed appreciably. Similarly, surface grinders and tool & cutter grinder can grind on the side of the wheel. You can do the same with your bench grinder just go easy – many have spring-loaded rotors. What you don't want to do is dress the wheel too thin or with too great an undercut.
Angle grinder wheels in comparison are very safe. They are reinforced and will take significant damage before they let go. You still need to respect them and they can still harm you if you lose a chunk from jamming or if the centre pops out but the damage is usually more evident before they'll let go and they do so in a much less catastrophic way.