Sharpening scrapers is something a lot of people struggle with. I've found this method to be easy and consistent.
This is what I will be using the sharpen this card scraper
- A block of wood with a thin slot cut through it that is longer than the scraper
- A single cut file
- A carbide burnisher
- A fine sharpening stone (DMT Extra Fine in this case)
- Honing oil or light machine oil
Apologies for the poor lighting. This is my "decommissioned" bench in the corner of the workshop I resign to messy tasks I don't want to contaminate my work - like cutting metal. The lighting works well for tasks, not so much for pictures
I start by slipping the scraper into the kerf in the block of wood. I've found the vise jaws either can't get a good enough grip on something this thin, or cause it to bow a bit. Another advantage here is I only have to loosen the vise a tiny bit to slide the scraper out to do the other side
Now I file the old burr off. I like to do this step every time. While I could simply burnish the surface again to roll the burr, I like to have fresh metal to do so. I am using a single cut file here. Notice the notches in the files teeth are inline with the scraper. The teeth run in the opposite direction on the bottom. This will ensure I get a clean, even, cut. I hold the file flat across the surface and make a few passes
To make things easier on the next step and to make sure the scraper is flat, I run the file straight across 2 or 3 times - similar to jointing saw teeth before sharpening. Once done I flip the card scraper over and do the same to the other side
I then smooth out the face on my XF diamond stone. I work both edges on both sides (4 faces) until the rough burr from the file is gone
Now to polish the face. I have a jointed block of wood I put on the stone to guide the scraper. I rub gently back and forth moving to different parts of the stone. Once all the file marks are gone and the surface is smooth, I flip and do the other side. It's important the face is smooth, straight and square. In fact polishing to a higher grit will result in smoother surfaces during use.
Here is where everything used to go wrong - turning the hook with a burnisher. This method makes it foolproof.
- First add a little oil. This will let me make gentle passes without sticking or binding anywhere.
- You'll see I'm choked up on the end of the burnisher. My fingers act as guides. I first place one hand (my right hand in this pic) up against the edge of the scraper, holding the burnisher at an arbitrary but about 5 degree angle.
- I now grab the other end of the burnisher with my left hand; keeping it up against the scraper. It acts as a guide.
- Now I take 2 VERY light passes and check for a burr. I know I am done when my fingernail just barely catches on the edge.
Flip and repeat x3
Done. Now I get nice shavings from the scraper instead of dust. If the scraper is leaving a rough surface, try polishing the edge with a finer stone, or leaving an even smaller burr. This process takes about 3 minutes once you get the hang of it