- Clamp the scraper to the vice
- File the old edges straight and square to completely remove the old burr. Use the filing guide if needed.
- Hone the edges with fine grade waterstone/oilstone/diamond stone/wet&dry sandpaper carefully maintaining the 90° angle, use a guide block if needed.
- Hone faces right by the edges with a same stone or abrasives as edges. To speed up the process, use the “ruler trick”
- Apply a drop of oil to the burnisher and on the edges of the scraper.
- Burnish the faces. Lay the scraper flat on your bench near the edge. With a low to medium pressure make a couple of passes with a burnisher to draw the burr out. Burnisher angle should be about 1° degree. Repeat on all the edges on both sides.
- Burnish the edges. Secure the scraper in a vice. Using the light pressure, swipe couple times along the edge first at 90° degrees and then progressively lower angles. The last stroke should be between 75-85° Do it both ways and on every edge.
For an aggressive cut, you can skip the honing step altogether. After filing the edge draw and turn the burr as usual.
For a finest cut possible hone the faces and the edges with the finest grade polishing stones. Draw and turn the burr only with modest pressure and angle.
Scraper sharpening tools
Tools needed to sharpen scrapers are:
- Single cut, fine, flat file
- Vice to clamp scraper blade into
- Sharpening and honing medium: water or oilstones, diamond stones or wet&dry abrasives.
- Dedicated burnisher of hardened steel or carbide.
- A drop of oil for burnishing.
You can also use a file guide which holds the file at 90° or 45° degrees to the scraper. I have used the Veritas Jointer & Edger with good results. For honing the edges you could also make guide block from wood with 90° and 45° faces to ensure the accurate honing angles
How to sharpen cabinet scraper without burnisher?
You can use chisel backs, screwdriver shafts, and old valve shafts as a burnisher for scrapers made from softer steels such as saw blades. Almost any smooth and polished hardened metal tool will help to turn the burr in most scraper blades. Burnisher hardness needs to be higher than that of a scraper for it to work. Scraper blades made from an old hand saw blades are hardened to 38-42rc and are easily burnished with almost any tool. Newer Veritas and Sandvik/Bahco scrapers are harder (around 50rc), and may need dedicated, hard burnishing rod to turn the burr properly.
Scraper blade stays sharp longer if sharpened properly
A scraper is a wood cutting tool like any plane. It needs to be properly sharpened, honed and burnished to work properly. Well-sharpened and honed scraper edge stays sharp longer than the edge that is only filed and burnished.
A sharp edge in plane, chisel and knife blade is defined as a zero radii interception point of two very smooth, polished surfaces. In well-sharpened scraper, the sharp edge is defined a likewise, but the intersection point is also with the help of burnisher bent away from the face surface to define the acute edge and adjust the cutting angle. To get this unbroken burr or hook the face and the edge must have flawless surfaces meeting at the sharp 90° angle before burnishing it.
File the edges straight and square
First, you need to file the edges clean and flat from any old burrs or in case of a new scraper, file the deformation caused by the die used to cut scraper out of sheet metal out. Clamp the scraper to the vice. Use the flat, fine, single cut file (Bastard/mill file). File the edge by holding the file at both ends. Hold the file as square as you can, draw file along the edge. File until all the nicks and dings are out of the metal and the edge is as smooth as a file can make it. Use the filing guide such as Veritas Jointer&Edger if needed.
The edges of the scraper can become work hardened after multiple burnishings. Be sure to file enough metal out of the edge to get past the hardened surface. The softer metal is easier to burnish
The edge can be filed also at 45° angle. You get only one usable edge by side but the edge is easier to turn and the resulting edge last longer and cuts more aggressively than 90° edge. Very thin scrapers used by violin and guitar makers are usually filed at 45° degree angle.
Hone the edges and faces
The filing leaves a rough surface and a serrated burr along the edges which needs to be removed by honing. I hone the edges with waterstones with the help of small hardwood guide block with 90° angle. That block holds the scraper at a constant angle to the stone while I move the blade back and forth along the stone. Scraper edge can quickly wear a groove in a stone if kept in the same place. I try to move the scraper/support-block combo in a slight angle to maximize the wear area in stone.
The surface quality of the faces or at least the surface right by the edges is essential for good quality cuts. Faces need to be honed mirror smooth for the best quality burr. The “ruler trick” works well and speeds up the process notably, only the essential part by the edge is honed and only a minimum amount of metal is removed. Lay a thin ruler down on one edge of the stone, and place the scraper on top of it so the opposite edge to the honed edge rests on the ruler. Move the scraper back and forth until the surface is ready, turn and repeat on the all edges.
For the finest possible cut, hone the edges and faces with the finest grade you have in your arsenal.
Once honed, the scraper can be used for finest work already but I recommend to roll and shape the edge further by burnishing it.
How to burnish cabinet scraper?
Burnishing the scraper is a two-part process. First, you draw the burr out by drawing the burnisher along the face the of the scraper. Second, you form and bend the burr/hook by drawing the burnisher multiple times along the edge.
Burnishing the face
Burnishing the face is easy. Lay the scraper flat on your bench near the edge. Apply a small amount of oil on the edge to be burnished. With a low to medium pressure make a couple of passes with a burnisher to draw the burr out. The angle of burnisher should be almost level with the scraper, the actual angle is about 1° degree. Turn the scraper around and burnish the other edge and do the same to another side by flipping the scraper over.
Burnishing the edges
Secure the scraper in a vice. Using the light consistent pressure, swipe couple times (this will vary depending on the hardness of the scraper and the amount of burr required but 3-15 swipes are usually enough with light pressure.) along the edge first at 90° degrees and then progressively lower angles. Aim between 75-85° The greater the angle of the last stroke – the higher the pitch when using the scraper and the more aggressive cut it will take. Remember also: The greater the angle of the burnisher, the more you will have to tilt the scraper to get it to cut
Burnish all the four edges along the length of the scraper.
How do you sharpen a gooseneck or curved scraper?
Curved scrapers are useful in many tasks. You can make your own shapes for certain tasks easily. Sharpening the curved scraper is similar to that for a rectangular one, faces and the edges are filed and honed and the burr is turned to get the cutting action required.
A good strategy is to prepare only the portion of the curve required. Sharpening and honing whole gooseneck scraper takes a lot of time and usually, you need only a small part of the curve. Many times the flat file cannot be used to joint the edge. Fine cut round files or drill grinding bits (diamond/silicon carbide/aluminum oxide) mounted on a pillar drill are a good way to prepare the edge instead.
Use very fine the wet&dry sandpaper around the dowel when honing the curved edge. Be careful to keep the edges square.
Faces of the curved scraper can be honed with normal bench stones.