Card scrapers, those handy rectangles of steel, are quick and easy to use; but like any cutting tool, they require sharpening to be effective. To achieve those miniscule hooks at the edge of the card that cut wood away so nicely, there are really only three steps involved.
But before you begin, it’s useful to make a simple jig to hold your mill file at a 90° angle to your card. Take a small block of scrap hardwood, slightly longer than your card scraper and two or three inches wide. Cut a kerf into to the wood to accommodate your mill file.
Step 1: Cleaning up the Edge
This step will square the edge of the card scraper and remove any scratches, pitting, or dings. Slip your mill file into your jig, and secure your card scraper in your bench vice. Run a Sharpie marker along the edge you will be working on to make it easier to see where your file is hitting. Place your mill file length-wise along the edge of the scraper with the side of the jig against the face of the card. While maintaining that perfect 90° angle of the file on the edge of the scraper, file length-wise. Take several passes while monitoring the edge color. When the ink from the Sharpie is gone, you are done. Your edge should be smooth and square. You may have a slight burr.
Step 2: Stone It
After filing the edge, you will want to polish it with a sharpening stone. Remove the card from your vice, press a small block of wood into the side of the card(to maintain the 90° angle) and slide the edge along your stone. Polish the edge, and then polish the side or face of the card. Start with a #1000-grit water-stone or comparable oilstone or sandpaper. Not just to make it shiny and attractive, but to perfect the place where the edge meets the side. That place where sharpness will live. After you have polished both the edge and side of the card, repeat with a finer grit; a #4,000 or #6,000 stone.
Step 3: Burnishing the Edge
This is the step wherein you create a tiny hook on each side of the edge. Some people use a screwdriver for a burnisher, and others use a burnisher built specifically for the task. The important thing is for the metal of the burnisher to be harder than the metal of the card scraper.
First burnish the face—one side, then the other. This will make it easier to turn the burr when you burnish the edge. This done, place the scraper edge-up once again in your vise, and holding the burnishing tool at 90°to the scraper, burnish up and down the edge. This should only require three to five passes. Then tilt the burnisher 5° to one side and take another three to five passes. Finally tilt the burnisher 5° to the other side and take another three to five passes.
You’re now ready to remove wood.
A couple tip-bits:
- Use a refrigerator magnet on the back of the scraper to insulate against the heat buildup when using
- If you sharpen all four edges of the scraper, number the edges to keep track of which one is which
- Scrapers work better on hardwoods than softwoods. On softwoods they tend to push and compress the wood fibers instead of cutting them.
This article is based on one found in the Wooden Word. If you’re not reading your issues, you probably can’t cut a straight line.