Make and Sharpen Card Scrapers
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How to sharpen a card scraper and even make one. Why make one when they’re so cheap? Well, sometimes you’ve got a piece that a typical card scraper just won’t get, or you have a batch project and a made to fit would really speed things up! In that case, making one is the way to go.
For this project I’m using:
An old handsaw
Milwaukee Variable Speed Angle Grinder (hack saw would be slower but work)
Milwaukee Die Grinder (variety of hand files also work)
Hand file
Burnisher (screwdriver works fine too)
A handsaw blade seemed to be about the right thickness to make some card scrapers. It was pretty similar to the one card scraper I could still find in my shop, so I assumed it would work well (and it did!).
If you want to order metal though, .035” seems to be the common size. If the metal is too thing it’ll be too flimsy, if it’s too thick then it won’t flex enough.
1. Cut the blade into card scraper blanks
Odds are you’re not looking to make a 24” card scraper, so that saw blade needs to get cut down!
I wanted a card scraper around 2.5” x 6” and a goose neck scraper. So I marked out the rectangle and traced the goose neck scraper I had on hand. If I didn’t have one to copy I would’ve used some random round objects around the shop to get some curves and free hand connected them.
For the actually cutting I used a diamond wheel in my Milwaukee Angle Grinder. Regular cut off discs work just as well, but they just seem flimsy to me so I don’t care for them. Alternatively, a hack saw and some elbow grease will get the job done!
2. Refine the blanks into card scrapers
The blanks were a big rough after cutting them out of the saw blade. For the rectangle it isn’t critical to me that the corners are square, but the sides do need to be flat!
I used the diamond wheel with my angle grinder and some careful eyeballing to flatten the edges as much as possible to save time hand filing. Then I pulled out the hand file and went at it until all the scratches from the diamond wheel disappeared. Then I did it on the rest of the sides.
For the goose neck and curved scrapers I used the Milwaukee Die Grinder with a carbide burr to get as close to the lines as possible. Which still wasn’t particularly even. Then I switched to the handfile and followed the contour.
It isn’t perfect, but I’ve had good luck fairing the curves with the hand file. The trick is to just keep turning it over the corner you want (not filing a flat spot) and it’ll just cut the high bits and skip the low points until it’s faired out.
Shadow trick with the Milwaukee Light Tower
To check my progress on the goose neck I’d put it behind a piece of paper and hold it up to the Milwaukee Light Tower so I could only see it’s silhouette. That helps keep all the scratches, discoloration, and reflections off the scraper from playing tricks with my eyes and much easier to see what needs work.
3. Sharpen the card scrapers
The process of getting the scrapers properly shaped produced a lot of uneven burrs around the edges. The first step of sharpening is to remove them, this should also be done occasionally after several sharpenings.
It’s as simple as running the file flat against both faces of the scraper and along the edge, being careful to produce a sharp shoulder and not round or chamfer the corner.
Now it’s time for the sharpening (or more properly, burnishing). The card scraper cuts by means of a tiny hook at it’s edge. That’s created in two steps. First the burnished it rubbed along the flat edge perpendicular to the scraper to squish out material on each side.
This creates a small burr on each side. The profile of a scraper has gone from an l to a T, on a tiny level. It should only take 10-20 swipes to create the burrs. Start with moderate pressure and taken a dozen swipes. If you don’t feel a burr, increase pressure until you feel a burr on the edge.
The second step is “turning the burr over” which changes the flange part of the T into a little hook. This is done by tipping the burnisher about 15 degrees or so and only taking a few passes, 3-5. Too many passes will curl the burr too far and create a P that won’t cut, instead of a hook.
4. Use and enjoy!
That’s it! The card scraper is ready to use. The trick to using a card scraper is getting a little bend in it. Put both thumbs in the middle and push it out, hold it and an angle to the material and cut! When you burnish, be sure to burnish all of the edges so when you work you have 4 sharp edges to work with before having to re-burnish.