When your concave and convex cabinet scrapers become difficult to run along the surface of your work or produces sawdust instead of shavings, this is the sign that they need sharpening.
The tools needed to sharpen the curved edges of the scrapers are a vice, a round file, a diamond stone, a burnishing tool, a piece of dowel, oil, a clean cloth and silicon carbide sandpaper.
Step 1 – Clamp scraper
Clamp the scraper in a vice, with the edge you want to sharpen sticking out.
Step 2 – Filing curve
Run the round file forwards and backwards over the edge of the concave or convex curve and repeat until smooth.
Step 3 – Sanding curve
Wrap the silicon carbide sandpaper around the dowel.
Run the dowel and sandpaper forwards and backwards over the edge of the curve. Repeat this action until the edge of the scraper is smooth.
Test the smoothness by carefully running your finger along the edge of the scraper.
Step 4 – Remove burr (rough edge)
Place the diamond stone on a level surface. Lie the convex or concave scraper flat on its side against the stone.
Run the side of the scraper forwards and backwards a number of times to remove the burr (rough edge) created when filing and sanding the edges. Repeat on the other side.
Step 5 – Apply oil
Apply oil to the burnishing tool.
Step 6 – Burnish sides
Place the scraper on a level surface. Hold the scraper with one hand, then with the burnishing tool, press down and rub against the sides of the scraper.
Turn the burnishing tool over a couple of times, to make sure you use most of the oil. Repeat this on both sides of the scraper.
Step 7 – Burnish curved edges
Clamp the scraper in the vice.
Run the burnishing tool along the curved edge of the scraper, either towards you or away from you. The burnishing tool only needs to go over the edges once or twice.
Step 8 – Wipe scraper
Use a clean cloth to wipe the edges of the scraper, to remove any leftover oil or material.
Step 9 – Test scraper
Using a scrap piece of wood, test the scraper to see if it’s sharp.
If the scraper produces shavings, then it is sharp enough. If it creates sawdust, it will have to be further sharpened.