Scary sharp
From Wikipedia, the free encyclopedia
Scary Sharp (tm) is a method of sharpening woodworking tools with sandpaper instead of conventional methods of oilstone or waterstone sharpening. The Trademark (tm) is intended to be humorous, not a legal device. It is now usually included whenever the title Scary Sharp (tm) is written.
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[edit] History of Scary Sharp (tm)
A sharpening method using sandpaper and glass is quite old, being passed down through apprenticeship woodworking programs as early as the 1950's - 1960's. Some believe that it pre-dates World War II.
The method was generally attributed to have been first described on the Internet in the newsgroup rec.woodworking by Steve LaMantia in 1995. However, a search of Google Groups reveals that there were several Scary Sharp (tm) postings prior to his. The method was made more widely popular by an article in Fine Woodworking Magazine.
[edit] The method
Any straight-bladed woodworking tool, such as a chisel or hand plane blade, can be sharpened with this method. Compared to conventional methods of sharpening, such as waterstone and oilstone, it is very inexpensive, fast, and easy to learn.
Materials required:
- An assortment of Wet / dry Silicon carbide sandpaper in various grits (120, 150, 180, 220, 320, 600, 1000, 1500, 2000). Sandpaper with pressure sensitive adhesive (PSA) backing is preferred
- A can of spray adhesive, such as 3M #77, if PSA-backed sandpaper is not available.
Start by gluing down a small piece (quarter sheet) of each sandpaper to the glass surface.
Flatten the back of the chisel by starting with the coarsest grit of sandpaper. Hold the back of the blade flat to the surface of the glass and stroke firmly, side to side. Make sure the pressure applied is even. After 20-30 strokes, hold the blade up and examine the back. An even pattern of scratches should be seen, with no areas unscratched. Use a paintbrush or a whisk broom to remove the metal debris from the sandpaper. If the scratches on the back of the blade are not even, repeat for 20-30 more strokes. Once an even pattern of scratches is seen on the coarsest grit, switch to the next finest grit, and repeat, working your way up to progressively finer grits. Each grit will leave a finer and finer set of scratches on the back of the blade. You want to effectively "erase" the coarser scratches with the next finer grit, before moving on. By the time you have finished with the finest 2000 grit sandpaper, you should be able to see a mirror reflection on the back of the blade. The blade is now flat.
Turn the blade over so that the bevel side is down, and clamp it in a sharpening jig so that the bevel is exactly flat on the surface of the glass. For most chisels, this angle is 25-30 degrees. Again, work your way up through the grits, coarser to finer, this time pushing the blade forward and back. Examine the bevel edge often to make sure that the bevel remains even and 90 degres to the side of the blade. Once the 2000 grit sandpaper is reached, there will be an even shine all across the bevel. Raise the angle of the honing guide by 2 degrees and repeat the lapping on the 2000 grit sandpaper. This will create a microbevel on the edge of the bevel. Then lap the back of the blade with the 2000 grit, removing the wire edge from the back of the blade. You may have to repeat this final honing, alternating between the microbevel and the back several times, to completely remove the wire edge. If desired, follow up with a leather strop.
[edit] Maintenance of a Scary Sharp (tm) edge
Unless the blade is extremely nicked, damaged, or dull, the coarsest grits can be skipped during future sharpenings. Trial and error will show you that you may be able to start out with 320 grit or finer sandpaper after the initial sharpening has been done. The back of the blade only has to be flattened once, but the final honing of the microbevel and the back should be done at each sharpening.
[edit] See also
[edit] External links
- The original rec.woodworking posting on Scary Sharp (tm)
- Link to the Scary Sharp (tm) article in Fine Woodworking Magazine
