hone the straight flutes or chip-lifters.While this is itself a problem there's more to it than that, it can also make the bit cut much less well and can lead to burning of the stock or worse, jamming, due to the cutting edges being a smaller diameter than the body of the bit.įor a Forstner the process is essentially this: The rule with large round bits like this is never to file the outside or circumference or you'll change the bit's size. Just as with augur bits you must be careful to sharpen only certain surfaces on a Forstner bit. It might seem obvious to use diamond needle files here, but IME many common diamond files are much too coarse for this job (150-300 grit, where you want something like 600 grit or finer). If your bit is better made it may be hardened or made from a harder/tougher alloy such as HSS in which case they will probably not cut well enough with needle files so any of the alternatives will have to be used instead. For a Forstner bit you'll need at least the round (rat-tail) and a flat or tapered file (the flat side of a half-round), and a triangular file may prove useful too. So I would recommend inspecting before you buy if at all possible. no guarantee of this today unfortunately! Price is not a reliable guide to quality with needle files, some cheap ones are well shaped and the toothing is cut well, while you'll read customer feedback on many files that cost more which indicates they can be neither. And for the flats a small slipstone can also be used, but it's commonly done today with a fine diamond paddle.Īlthough bits are usually made of tool steel they're not generally hardened to the same level as other cutting tools so can usually be comfortably cut with a steel file, just as with augur bits used with a brace.Ĭonsequently the whole job can in theory be done just with files, a set of needle files being sufficient as long as they're of decent quality. These days in place of a round slipstone many use a conical burr chucked in a pillar drill or a Dremel-type tool, or any similar handpiece. The traditional tool for sharpening bits is a type of file, although with Forstners a round slipstone was often a necessary addition to tackle the bevel on the curved rim. Even if you glue it to a small slips of wood to make rudimentary files from it these won't be particularly stiff so may not give you the accuracy you'd want to properly sharpen a bit, where as much as possible you want to maintain the existing geometry of the factory grind.
I don't think you can sharpen a Forstner bit accurately enough with abrasive paper.
0 kommentar(er)
