Re: "Finger" grinder - what the heck do they call them
Maybe you mean a power file. It's like a belt sander, but the belt is only 1/2" wide or 3/4" wide depending on the type.
Once you hold it in your hands, you think you're holding a small machine-gun. My first one was an electric powered Black & Decker that I bought in their shop in Slough, England. The one I use now is the larger type and is driven by compressed air. See photo of me in 1987 or '88 using the B & D.
Check out Harbor Freight.