hey everybody in today's how-to video I am going to show you how to ring test a grinding wheel from a bench grinder bench grinding wheels can be very dangerous things they can have microscopic cracks in them which will cause them to explode at very high rpms so you can take a bench grinding wheel off of a used bench grinder or even a brand new one out of the box and even though it looks like it's a good grinding stone it may not be it may have a microscopic crack and the first time you use it it could just explode and send shrapnel flying across your garage and into your face so this is a very quick and simple test that will tell you if the grinding stone is any good or not and if it has any microscopic cracks in it or not a ring test gets its name because when you test it you'll hear a very high-pitched ring and if you hear a high-pitched ring when you do this it means that the stone is good if you don't hear a high-pitch ring then the stone has cracks in it and is a very dangerous stone you do not want to use this so this is something that you should do even if you have a used grinder or you get brand new grinding wheels right at Sears on the Shelf you want to do this test for your own safety in order to do this test really all you need are two screwdrivers in a grinding stone this is a good grinding stone this grinding stone will have a high-pitched ring and what you'll do is you'll the the hole in the center of the grinding stone you'll take a screwdriver and you will just suspend the grinding stone in the air and then with the other screwdriver you'll take the plastic handle and what you're going to do is you're going to tap it at the very bottom the very top left right and then you'll turn it about an eighth of a turn and do that again that'll allow you to hit it on eight equal parts just imagine this is a piece of or actually a pizza and you cut it into eight slices you want hit every slice so you'll take the end of your screwdriver and you'll just tap it and you'll hear a real high-pitched ring and then above aside over here and then just turn it slightly and do that again that's a ring test and because you heard that high-pitched ring this is a good grinding stone there's no cracks in it now let me show you a grinding stone that is not safe and the reason I know this grinding stone is not safe as I actually cracked it in half and then had to glue it back together so this is not a uniform stone it looks like a uniform stone however it is really two pieces and because it is not a uniform stone it won't have that same high-pitched ring that the good grinding stone had so if you take the grinding stone off of your grinder where you take it out of the box at the store because you know tractor trailers run over potholes going down the interstate stop boys drop boxes on the way out to the shelf plenty of things can happen to that grinding stone in between the factory and you so this is something you can do before you even purchase it just take it out of the package take two screwdrivers off the shelf and save yourself a lot of time in trouble by doing this in the store but you'll do it the exact same way and this one you will not hear a high-pitched ring and if you notice the difference between the two that is not a high-pitched ring that's a adult thud and then you have your good grinding stone so there you go that is how you ring test the grinding stone to verify its integrity if you hear the high-pitched ring you're safe if you do not hear the high-pitched ring either don't buy it or if it is on your grinder or you have it in your workshop to use in the future throw it in the trash because they will explode a smaller grinder will run at about 3400 rpms a large grinder like let's say a 10-inch bench bench grinder will run at about 1700 rpms but that is still extremely fast and when you touch a piece of metal to that stone it will cause it to explode and the little pieces of it will just go flying into you and across the room so that's your tip of the day if you liked this video please click like if you like my channel please click subscribe thanks for watching