This thing has enough power to hurt you if you tighten it, so treat it with respect. They last almost forever. I used one in our motorcycle shop to sharpen cylinders for 10 years before brushes were even needed. I bought another one because I couldn't wait for the brushes to arrive and I still use them. I bought this to replace the one I lent my carpenter when he didn't want to give it away and paid myself to buy a new one. i love them all No doubt I've never had a stronger, more powerful drill bit than this one, and I've had them all.