by David J. Marks
Scrapers are one of my favorite hand tools and I find them to be indispensable in the woodshop. They are made from thin pieces of steel, and come in a variety of sizes, shapes, and thicknesses. The one that most people are familiar with is the rectangular scraper that is approximately 21/2” by 6”by 1/32”. The challenge that many woodworkers have with scrapers is learning how to sharpen them properly so that the scrapers remove shavings as opposed to simply producing sawdust. The following is a description of how I like to sharpen my scrapers.
The first step is to file the two long edges. Clamp the scraper in a vise and use a single-cut mill file to flatten the edges. Start by holding the length of the file parallel to the length of the scraper and then angle it outward approximately 20 degrees or so. This places the file in a slightly diagonal direction so that as you draw the file across this will help the metal filings to clear. The goal is to create a straight edge that is 90 degrees in the cross section.
In talking to many woodworkers, I have found that after filing the edge they go to the burnisher to raise a burr. The problem that they encounter is the burr does not last long or that it does not cut nice shavings. The reason for this is that the file leaves a series of microscopic serrations in the edge. The method I use involves a further investment of time, but it definitely pays dividends in the results; shavings as opposed to simply sawdust. After filing, I use Shapton ceramic Japanese water stones to flatten and polish the sides and edges of the scraper. I start with 1000 grit which is their coarse stone, then I use 5000 grit which is their medium stone, and finish with 8000 grit.
Polishing the sides is fairly straightforward. Lay the scraper flat on its side and use downward finger pressure to hold it flat on the stone as you work it back and forth. Polishing the two long edges is more challenging. The difficulty is in holding the scraper vertically on the stones. If you rock it you will round the 90 degree corners and it will not cut. My simple solution is to use a block of UHMW plastic jointed to 90 degrees to support the scraper. I find this works well and does not damage the stones. Be sure to work the scraper diagonally to spread the wear over the stones.
For burnishing, I like to rub some lightweight honing oil on the scraper and burnisher to reduce friction. Begin by laying the scraper flat on the workbench and hold the burnisher a few degrees off horizontal as you stroke it. This preparatory stage is called raising the burr. Next, I hold the scraper in one hand and the burnisher in the other so that it is approximately 5 degrees down from horizontal and approximately 5 degrees forward from perpendicular to the scraper. Using moderate pressure I draw the burnisher across the scraper about ten times. At this time I usually have a fine burr that cuts quite well. I find that I can reburnish the edge as needed almost a dozen times before having to go back to the files and stones.