Grinding Metal: "What Could Possibly Go Wrong?!"
When working with metal, there are plenty of things that can go wrong while grinding that can make a difference in your safety as well as the quality of the work.
One issue is what you put on your grinder. You usually get a stone grinding wheel when you buy a grinder that's really similar to the grinding stone on a bench grinder. It takes off lots of metal, but it leaves really deep gouges when it does. Depending upon what you are doing - are you grinding down welds, grinding off paint or ...? - that affects what grit you're going to need.
Do you need a stone wheel or a soft pad? Soft pads are like strips of sandpaper glued to a backing. Kevin loves them because they do a much cleaner job of grinding, they're quieter, and they don't leave deep marks.
Kevin shows a 60 grit soft pad, which is pretty rough in the beginning, but after you use it a minute or two, it takes the roughest of the grit off. The 40 grit is going to leave gouges and scratch marks, so if you use it to, say, grind a weld, you have to go to the 60 grit to clean up those marks, then to an 80 grit, and finally to the 120 grit. Start out with the right grit for the right job.
Also make sure you are using the right size grinder. Kevin admits he sometimes will grab his big, 7-1/2" grinder because the smaller, 4-1/2" grinder is just too slow. He wants to get the job down more quickly, but then ends up grinding holes through 16 gauge steel. The big grinder takes two hands to operate because it wants to take off across the metal. When the Voice uses it, it's like somebody riding a floor buffer. She uses the smaller grinder with two hands, while Kevin holds it with one, using it almost like a detail grinder.
Next, Kevin shows a cut-off wheel from an abrasive chopsaw. The hole in the center of it is the same as on the 7-1/2" grinder. Kevin says he's taken the guard off the grinder and put on the cut-off wheel to use it like a portable chopsaw. He still has the scars on his leg from where he slipped, and the blade went through his jeans and into his leg. Kevin says, "Please don't do that." He says 7-1/2" Skilsaw blades also fit the 7-1/2" grinder, so use one of them if you want a portable chopsaw.
Speaking of taking off the guard, it's there for a reason. If you are using the grinder with the guard between you and the work, there's less chance you'll set yourself on fire. Kevin has seen it happen: without the guard, the sparks set someone's shirt on fire. If you have to take the guard off, put it back on as soon as possible - that safety equipment is provided for a reason.
One of the biggest things that can go wrong with grinding, especially for newcomers, is that they forget to look at the arrow on the grinder case. The arrow indicates which way the grinding wheel is turning. It's also intended to keep you from grinding onto a piece of metal instead of off of the metal so you don't gouge it. If you have an 45-degree corner with a weld and you weld onto it, you grind the corner down and gouge it. If you grind off the top of the metal you get a nice surface, then grind up to get a sharp corner that you can then just touch with your grinder to soften it.
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