Buttery-smooth wood surfaces ready for finish:
That’s what a well-sharpened card scraper can give you.
But when I first started woodworking, burnishing that perfect hook was easier said than done.
Now I’ve mastered the process. And I keep a card scraper (often called a cabinet scraper) in my apron at all times.
Regardless of your experience level, you should too.
To help you succeed where I struggled, I’m going to walk you through the steps for sharpening a card scraper — and give you a few tips for success.
Ready for ultra-thin shavings with zero tearout, and wood so smooth it slides through your fingers like a bar of soap?
Read on, my friend.
TOOLS FOR SHARPENING A CARD SCRAPER
Burnisher: A burnishing rod is just a round piece of steel harder than your card scraper (an old screwdriver can work in a pinch). We sell a super fast-working, rough carbide burnishing rod from Wood by Wright.
File: Not essential, but it speeds up the process. I fashioned a jig that’s a square piece of stock with a kerf that holds the file at 90°.
Sharpening stones (any higher grit is fine, just not coarse): I prefer diamond stones since the top edge of a card scraper can leave grooves in waterstones or tear sandpaper
Vise: For holding your card scraper upright.
THE “SCIENCE” OF CARD SCRAPER SHARPENING
Unlike with chisels or hand plane blades, sharpening a card scraper isn’t about creating a razor sharp edge.
You want the edges to have a steel “hook,” or curl — which is a burr that’s been folded over with a burnisher.
It’s almost too small to see — but this hook makes ultra thin shavings with no tearout, regardless of grain direction or wood species.
There are 3 basic steps to sharpening a hook onto a card scraper:
- Squaring the edge
- Pulling the edges up, or elongating the burr
- Rolling the edges over, or folding the burr into a hook
Squaring the edge isn't necessary every time you sharpen: you can roll over the burr 4 or so times before needing to square the whole thing again.
But if you’re starting from scratch, follow this entire process for the best results.
HOW TO SHARPEN A CARD SCRAPER
I’m going to walk you through the sharpening process without using any jigs.
If you want a foolproof system, this video explains how to build a simple and inexpensive sharpening jig (and here are the free plans).
I’m going to explain how to sharpen a rectangular card scraper — which is what I use 99% of the time.
You can follow these same steps for sharpening concave or convex edges. Just rotate your card scraper as you burnish the hooks.
Also, note that a rectangular card scraper has 4 cutting edges. Repeat these steps as necessary to make sure they’re all sharpened.
STEP 1: SQUARE THE EDGE
Again, you don’t need to do this every time you sharpen your card scraper.
But when you do, take the time to get it nicely polished.
The rougher you leave it, the more failure points will be in the burr — and the more likely your hook will break.
Add a little oil to your card scraper edges, and start by squaring the top.
I file until there’s a fresh clean surface and I can feel the beginnings of a burr on each side.
Then I file the sides (making sure to do so at 90°) until the burrs are gone.
You can skip the file and just use a sharpening stone — but if you do use a file, don’t skip the sharpening stones. The file leaves deep scratches you need to clean up.
Give the corners of the card scraper a light roundover.
This keeps them from digging into your work down the road.
Now polish all 3 edges on a sharpening stone. I prefer a diamond stone because the top edge of a card scraper can create grooves in your waterstones.
Matt Estlea tip: If you only have waterstones, sharpen on the edge of the stone instead of the face. It’ll save you from marring the faces you need flat for sharpening chisels or planes.
You can use a square block of wood to keep your card scraper at 90° when polishing the top edge.
Once the top’s nice and shiny, polish the edges to get rid of any burr. Just make sure to keep it flat on the stone.
Repeat this step on both sides of the card scraper.
STEP 2: ELONGATE THE BURRS
Time to grab your burnisher.
Set the card scraper flat on your bench, about ⅛ inch (3 mm) from the edge. Hold it in place with one hand.
Now hold the burnisher at around 5°-15° to the card scraper.
The exact angle isn’t super important. What matters is that you pick an angle and stick to it. Lock that wrist.
Using light pressure (about what it takes to push an elevator button), slide the burnisher back and forth over the edge. About 10 times total will do.
It’s ok to hit the corners. You should hear a rhythmic sound of ka-slink-ka with each pass (onomatopoeia is tricky).
Repeat this for all 4 edges.
Use light pressure with the burnisher, both during this step and the next.
When I first started, I pushed too hard and didn’t get good results.
The pressure you would push a crosswalk button with is about perfect. Light pressure is key to good results.
STEP 3: FOLD THE BURR
This is the part people get hung up on, but it’s actually pretty easy.
Place the card scraper in your vise.
I like to hold my burnishing rod in two hands at this point so I can really lock my wrists and maintain a consistent angle.
Again, anywhere from 5°-15° is fine — but consistency is key.
Using LIGHT PRESSURE, run the burnisher back and forth over one edge.
Do this around 6-8 times.
If you run your fingers against the edge, you should be able to feel the hook. You can even hear it catch on your fingernails (and whisper to you in the night).
Repeat this step for all 4 edges.
Use a sharpie to draw little arrows pointing to the newly sharpened edges of your card scraper.
Once the sharpie fades, you’ll know it’s time to resharpen. It’s not an exact science — but it works.
HOW TO KNOW IF YOUR CARD SCRAPER’S SHARP
Time to test your edge.
A well-sharpened sharp card scraper should create wood shavings, not dust.
You want to see ultra-thin shavings, almost like a hand plane makes.
If you’re getting dust, adjust the angle at which you’re holding the card scraper.
If you get dust no matter the angle, you don’t have a good hook on the edge — probably the result of pushing too hard with the burnisher.
Try again until you’re getting thin, curly shavings.
Once you’re there, you can start making crystal clear surfaces ready for finishing.
GET HOOKED ON CARD SCRAPERS
Once you’ve mastered the sharpening process, your card scraper will become an integral part of your workflow.
Take one pass with a freshly folded burr and I promise — you’ll be hooked.