Air-powered die grinders are a multi-purpose, save-the-day tool, useful even if your shop is a dirt-floored corner of the machine shed. Get a decent 1/4-inch shaft die grinder, equip it with a set of carbide-tipped bits and a mandrel for a 4-inch (diameter) cut-off disk, and you’ll be able to enlarge or “slot” existing holes in metal. With the carbide bits you’ll be able to smooth rough edges of metal you’ve cut with a torch, clean up the ends of hex, square or round shafts, ream out bolt holes and precisely remove increments of metal from just about anywhere or anything.
Install the mandrel with an abrasive “cut-off disk” and you’ve got a high-speed mini-hacksaw, perfect for cutting off bolts, splitting nuts or bearing races, smoothing the edges of sheet metal or cutting/scoring flat steel. Once you get used to having a die grinder and become aware of what you can do with it, it will become a go-to tool in your toolbox, even if your toolbox isn’t very big or well-equipped.
I’ve accumulated several die grinders over the years, and find it handy to keep one equipped with a cut-off disk and another one equipped with a carbide cutting bit--it just saves time swapping bits and wheels when I’m in a hurry. An older, nearly worn out die grinder is equipped with a mandrel that accepts a rubber 4-inch (diameter) buffing pad outfitted with sanding or “Scotch pads” for removing gaskets, buffing away rust, or polishing small metal pieces and parts.
My favorite die grinder is a Mac Tools model that is reversible. Being able to reverse which way the sparks fly when I grind metal is a very useful feature, especially for safety and comfort. Which raises the issue of eye and ear safety--I’ve learned the hard way that eye and ear protection are essential accessories when using a die grinder, even if only for a few seconds of “touch-up” work. The high speeds of die grinders cause a lot of ricochets from metal filings that favor either full-face safety shields or goggle-type eye protection. And the high-pitched howl of a die grinder will leave unprotected ears ringing for hours.
Figure on spending $100 to $200 for a quality die grinder. Be sure to use air tool oil before every use---they’re a high-speed tool that requires lots of lubrication. Carbide bits cost from $50 to $250, depending on how many, and how fancy they are. Mandrels for cut-off disks and sanding/polishing disks are $10 to $30.
It’s all money well spent. You’ll be surprised how often you use a die grinder, once you understand its potential. I even found multiple uses for one of my die grinders during a bathroom renovation at home. I’m pretty sure no plumber or carpenter ever used a die grinder for those particular purposes, but...I never claimed to be a plumber or carpenter.
