By Joshua Farnsworth
Have you struggled to sharpen a card scraper? If so, don’t feel embarrassed! Years ago when I first started using a card scraper, I certainly struggled too. In this video and article I share my simplified method for sharpening a woodworking card scraper, in five easy steps. And I share a little trick that I discovered that helped me to get my card scrapers cutting every single time. But first, let’s answer a couple important questions:
What is a Card Scraper, and why do you need one for Woodworking?
A card scraper is a thin rectangular sheet of flexible steel that has temporary high-angle hooks, or burrs created on all four long edges. A card scraper is used by flexing it between your fingers (with your thumbs on back) and pushing it along the board to smooth the wood, by removing thin wood shavings in areas of difficult wood grain. A card scraper excels where a traditional handplane may cause tear out, and where sandpaper may leave a fuzzy surface.
What Tools do you need for Sharpening a Card Scraper?
There are a few tools that you need to sharpen your card scraper. If you sharpen other woodworking tools, then there’s only one other tool that you’ll need. Here are the tools that I use to sharpen card scrapers in my woodworking school:
- Card Scraper: As mentioned above, this is a rectangular piece of steel used to shape or smooth areas with difficult wood grain. Card scrapers can be purchased or can be made by cutting up an old hand saw.
- Burnisher: A hardened and smooth steel rod that draws out the burr (see step 4), and turns the hook (see step 5). This is the only specialized tool I use for sharpening card scrapers.
- File Jointer: A piece of metal or wood that holds a mill file at a 90 degree angle. I use the file jointer that I sharpen my handsaws with.
- Mill File: A metal file used to flatten, or joint the edges of a card scraper. I also use the mill file that I sharpen my handsaws with.
- Honing Stones: Natural or synthetic stones used to smooth and polish a card scraper before drawing out the burr. These are the stones that I use to sharpen my handplane irons and chisels. I prefer water stones for this job, but oil stones or diamond stones can also be used.
Here are Links to my Card Scraper Sharpening Tools:
How do you Use a Card Scraper?
To use a card scraper, grip the card scraper between your two hands and push on the back of the card scraper with your two thumbs until it flexes slightly. Then push the card scraper forward, tipping it forward at an angle. Experiment with the angle until it cuts. If it produces nice shavings, like those produced by a sharp handplane, then go ahead and use it. If it doesn’t produce nice shavings, then proceed with the steps below:
5 Steps for Sharpening a Card Scraper
Step 1: Test the Card Scraper
The first step in setting up a card scraper, is to first test it to see if it actually needs to be fully resharpened. If it produces nice shavings, then it can be used for scraping. But if the card scraper produces dust or poor shavings, then the you either need to turn the hook again (you can do this 1-3 times before resharpening), or start all over preparing the card scraper. The following steps show how to “prepare”, or start sharpening a card scraper from scratch:
Step 2: Joint the Edges
The next step is to joint the two long edges of your card scraper to ensure they are flat and that the old burrs are completely removed. I use a metal jointer that holds a bastard mill file at a 90 degree angle and push the jointer along the card scraper 2-3 times until I can feel that it is cutting the entire length. You can also use a wooden block to hold your file.
Step 3: Remove the File Burrs & Smooth the Scraper
In this next step I remove any burrs created by the file, and polish the card scraper. I alternate rubbing the faces of the card scraper on a 1,000 grit water stone, about 1/2-inch in from each edge.
I then flip the card scraper vertically and remove any burrs on the edges. But I hold the card scraper at a skewed angle to prevent creating a groove in your honing stone. Several passes on each side is all you need, before moving to a 4,000 grit stone. I repeat the same process on the 4,000 grit stone until the card scraper feels smooth and burr-free. You really should watch my above video to make this step more clear. Now you have what I call a “prepared” card scraper, all ready for drawing out the burr (step 4) and turning the hook (step 5).
Step 4: Draw out the Burr
After drying off the card scraper, it’s time to use the hardened steel burnisher to “draw out” the metal on the card scraper. Running the burnisher flat on each edge two or three times will harden and stretch out the metal. This prepares the metal for turning the hook. Do this on all four long edges.
Step 5: Turn the Hook
Next, move the card scraper so that it just overhangs the edge of the workbench. Place your burnisher upright, against the card scraper, then tilt it a couple degrees toward the card scraper. Then push the burnisher forward, applying pressure to the card scraper as you move along, from front to back. Do this one to two times, and then use your fingernail to feel all along the new burr.
If your fingernail catches, and even flakes off, then you know that you have a properly turned hook. If part of the edge catches your fingernail, but other parts do not, then just return to the non-cutting sections and turn the hook more on those sections. This is where my method differs from others that I’ve seen: I turn the hook by feel, rather than just hoping that it has been turned. This is what your edge should now look like if you’ve done both sides:
Repeat the process on the other two sides, and you will have four cutting surfaces that will do an excellent job in smoothing the areas with difficult wood grain.
What tips do you have to successfully sharpen a card scraper? Share your comments at the bottom of this page…