This tool is really quite simple. It is also very ingenious. I often wonder how it came about. Who invented it? It is also very cheap. I got mine for about $5. They are of Sandvik steel but I don’t think the manufacturer is critical.
It is called a cabinet scraper. Cabinet scrapers are made of mild steel. They are less than 1/16″ thick and are about the size of a filing card . To make one ready for use you first”burnish” a burr on each edge.
Cabinet scrapers are billed as the answer to sandpaper. To use one you draw the sharpened scraper across the surface of a rough piece of wood. You can feel it dig in and you will see tiny shavings appear. It acts almost like a mini-plane.
Cabinet scrapers remove material much faster than sandpaper and leave a smoother surface. They are especially handy when you are applying a feather lap to a plank. I tend to round the lap when I only use a block plane. When I use a cabinet scraper as the final step in cutting a lap I have great control over the amount I am removing. The final lap is absolutely flat with no rounding. I also use a scraper for finishing off the inside of the hull prior to varnishing. In that case I use a scraper with a curved blade to conform to the concavity of the hull.
They are also indispensable in removing varnish “runs”. Have you ever tried to remove a varnish run with sandpaper? It is next to impossible. A scraper makes short work of it.
The trick to success with scrapers is to sharpen them properly. I tried the old way using a burnishing iron with limited success. Then a tungsten carbide burnisher came on the market. It really does a great job of sharpening a scraper.
The steps in sharpening a scraper are as follows. First, remove the old edge by sanding or filing it away. Then clamp the scraper to the bed of your band saw or other power tool so that it hangs over the edge by about a 1/2 inch or so. You can apply some motor oil to the top surface if you like. Now run the carbide burnisher across the surface so that it is parallel to it. Apply moderate pressure and run the burnisher back and forth at least 10 times. This will form a burr on the edge of the scraper.
Now you need to turn the burr so that it is at right angles to the plane of the scraper. Do this by running the burnisher along the exposed edge of the scraper. Angle the scraper at slightly less than 90 degrees to the scraper. This will turn the burr so that you now have a cutting edge. The scraper is now ready to go.