A burnisher to sharpen scrapers is widely available from many manufacturers in several variations. What works very well for me is one that I developed. As far as I know, this is unique.
The rod was made of carbide in sub-micron grain size at my request by Innovative Carbide Inc. in Pennsylvania. The hardness of this material is rated 91-92 in the Rockwell A range! This is significantly harder than a 70 at the top of the C range. C is used for tool steels such as chisels, plane blades, and scraper burnishers, all usually about 59 – 64 C.
This hardness allows easier pressing on the scraper steel which is typically 48 – 52 C.
The rod is 3/16” in diameter. This works very well. The narrow rod, especially at 91-92 A, more efficiently presses out an angled metal edge on the scraper. Less effort is required than using a rod that is twice the thickness and not as hard.
After 20 years of use, the rod shows no wear. If I built it again, I might choose 1/4” diameter for a little more control, but certainly not wider than 1/4”. Anyway, the 3/16” works well and is exceptionally useful in small curved scrapers.
The 3/8” diameter, especially at the typical 60 – 62C found in almost all commercial burnishers, does not give as much effective power in pressing out the cutting edge.
The thin and very hard rod in my burnisher gives great contact and control in sharpening a scraper.
The rod is actually 12” long, which is more than I needed. I used it with 5” in a wooden handle. I was never totally happy with the 7” of exposed working length. I changed to 4” of length in each of two small wooden handles. This leaves 4” to work with. Perfect.
I can push the tool at an angle and move down the range of the angle. This is very effective in making an excellent edge in the scraper. It also works well to flatten a failing edge over the side of the scraper in intermediate-stage sharpening.
To make all of this work well, I have long used a vise based on what is shown in the 1979 book “Tage Frid Teaches Woodworking.” I added a platform setup to hold it all in the workbench tail vise. I will review my design features in an upcoming post to add onto an old post about that.
Burnishers I have found online, worth noting: Blue Spruce makes a two-handled burnisher with a 3/8” rod of “textured high carbon tool steel.” O’Skool also makes one with two handles. The 3/8” rod is 61C “chrome molybdenum.” The working length of the O’Skool is listed by photo as 2 11/16”, and the Blue Spruce looks about the same.
My scraper sharpening burnisher tool gives easy, comfortable, and very effective sharpening and flattening.
