Best Method for Sharpening Forstner Bits?
Issue: Issue 306
Posted Date: 7/31/2012
I use Forstner bits a lot in my woodturning projects and was wondering if you have a good/simple/best method of sharpening/caring for them? - Bruce Dixon
Tim Inman: There is a disappointingly low-tech answer for your question that is also probably the "best" answer. You need a clever little specialty file. It is called an "Auger Bit File." Once very commonly stocked in "old-time" hardware stores, back when every workshop had a set of augers and a brace on hand, it is now likely an Internet specialty purchase. It is designed to sharpen -- well, auger bits. The file has two business ends. One end has the file cutting teeth on the flat surfaces and is smooth on the edges. You can file right up to an edge without cutting into it. The other end of the file has cutting teeth on the edges, but not on the flats. You can file an edge without nicking the other sharp edge touching it. A Forstner bit has exactly the same sharpening problems that a good old auger bit has. The little file is about 6 inches long, and it will become your new best friend. Handy for many things. If the circular scoring ring or cutting edge needs touching up, then you'll need something like an abrasive cone in a tool like a Dremel, etc. This shouldn't be needed very often, though. Remember, the scoring ring bevel ALWAYS faces the inside of the bit. NEVER grind the outside edge of that ring.
Chris Marshall: Bruce, Rockler sells a kit for sharpening Forstner bits that includes two honing stones, a file and instructions for sharpening either carbide-tipped or multi-spur Forstner bits. Click here to learn more.