Sharpen Your Cabinet Scrapers

Cabinet scrapers are traditional tools that will elevate your woodworking from the ordinary to the sublime. They won’t help you cut joints any better or make your glue-ups go faster, but what they will do is provide you with a smooth surface that will make your finishes stand out. You know that ‘look’ you see in coffee table books, or on antiques at the museum? Well, that can be yours if you know how to prepare your project for finishing – and use a proper finish of course.

Now, this article isn’t about how to apply a finish, nor is it meant to persuade you to use cabinet scrapers. I assume that if you are reading this, you must already be interested so I will get to the heart of the matter – sharpening. Aside from a lack of knowledge of scrapers in general, an inability to properly sharpen them is the main reason they stay quietly buried in a long forgotten drawer. Hopefully this little discourse will find your scrapers out in the open, and in use.

A cabinet scraper is just a hard, flat, rectangular piece of tool steel (curved varieties are available too) and sharpening one is a three step process: jointing, honing and burnishing. The first two steps flatten and polish the edge of the scraper. In the third step a very hard metal rod is used to roll a burr on the edge. This burr, depending on how well you jointed and polished the edge, is razor sharp and when presented at the correct angle to the wood, shaves off little fluffy curls leaving the wood smooth enough you almost won’t need to sand. Of course, every tool leaves a mark and some sanding will be required unless you wish to leave the scraper’s fingerprint on your finished piece. You’ll know right away if the scraper isn’t sharp because all it will make is sawdust. In order to follow the three steps from above, you will require a very few items.

First, you require a scraper. They aren’t very expensive and can be had from Lee Valley for a few dollars apiece, or around $12 for a set of four. Lee Valley sells only good scrapers and you won’t be disappointed. For the moment we’ll discuss just the rectangular card scrapers although sharpening a gooseneck scraper only differs in that you have to work freehand. You will find that scrapers are all about the same general size, but their thickness varies. A thicker scraper yields a deeper burr and takes a heavier shaving. The thin scrapers make light, wispy finishing cuts. Thinner scrapers are easier to bend and I find them less fatiguing to use so, in my shop, they see more use.

Next, you will require a flat mill file. A single cut bastard file, around eight inches in length, will do fine. The file is used to joint the edge of your scraper. To hone it you need a stone of some description – which I’m sure you already have. For scrapers I prefer to use an oilstone that is one inch wide and three inches long. Mine is made for sharpening penknives and I like it because it fits in the same wooden jig I use for filing.

The wooden jig I use is the same as that described on Ralph Brendler’s scraper sharpening page (click here for a diagram of the jig). You can find the dimensions here. Why did I go to the trouble of writing all this instead of just sending you there in the first place? Darn good question! Actually, I wrote this page because, although I like Ralph’s jig, I disagree with his method of sharpening scrapers and I find that, with my equipment, my way, I can sharpen a scraper much faster. To make his jig you just need a piece of hardwood two by two by eight inches in length with a ledge cut in the top. I sized my block, then cut the ledge by running it through the tablesaw with the blade set about a quarter inch shy of cutting all the way through. Be careful while you do this. You lightly chamfer the edge under where the file sits to accommodate any burr that may be on the scraper before you joint. The opposite corner is chamfered to make it easier on your fingers.

You will require some kind of tool for burnishing. I use a Veritas burnisher from Lee Valley, but you could use a valve stem out of an old car. Some suggest using a screwdriver shaft, but most of them are not made of sufficiently hard metal and all you will do is mess up your screwdriver. Your scrapers won’t be very sharp either. Make sure you have some oil on hand. I have a small bottle of compressor oil I keep at the bench for burnishing and for lubricating my brad nailer.

Lastly, although not strictly necessary, the process is made simpler if you have some kind of metalworking vise. I bought the one in the pictures from Home Depot for under $20. You could also pick one up on Ebay but the shipping charges would be horrific. The next vise I buy will probably be out of the Harbor Freight catalog. I’m not a blacksmith so I don’t need the Cadillac of vises.

If you are using your scraper for the first time, you need to do an initial flattening. Unless you run over it with a forklift, you will never need to repeat the following on this scraper.

Like the back of a new chisel or a plane iron, you want to ensure that your scraper is flat before you use it. Now, before we proceed, let me point out that I’m not that obsessive-compulsive about flattening. Some gents spend needless hours laboring over sheets of sandpaper-covered plate glass just flattening. I do spend more time with the back of a chisel because it determines the chisel’s ability to cut a straight line. I spend a little less time on plane irons, as they only need to be flat for part of the iron above the mouth. With a new scraper, I am just trying to ensure that there are no burrs anywhere on the face or edge of the steel that may interfere with it’s ability to cut. So I spend a few minutes – probably no more than ten – just cleaning it up.

I start with my coarse 250X waterstone and clean up the sides. I lay the scraper on the bench and smooth the edges with the side of the 250X waterstone by moving the scraper back and forth. I repeat this process on my 1000X waterstone, then I move on to jointing.

You could just as easily perform these tasks on wet/dry abrasive and a sheet of plate glass, or some other flat surface. Oilstones would also work. Use whatever sharpening tools you have at hand. I’m a firm believer in finding a way to make what you already own work to fit the situation.

To joint means to make a surface straight and flat. Jointing a cabinet scraper is the same as jointing a piece of wood; you just use a file and your handy wooden guide block. Before you start, mount your scraper in the vise and make sure one inch, or a little more, is protruding from the jaws. Place the file in the notch on top of your wooden jig and, while holding it firmly to the jig with your index finger, bring it up to the scraper. You want firm contact between the side of the jig and the scraper to ensure that the file stays perpendicular to the scraper face. A few, full strokes will flatten the edge. Don’t move the file back and forth like a brush, set it down and make a firm forward stroke, lifting up before you get to the end of the file. Lift it and reposition it where you started before repeating. I always get the best luck filing in only one direction.

Notice that I use the fingers of my free hand to support the side of the scraper. If you push too hard the scraper may begin to twist when left unsupported. I use only as much finger pressure as necessary to keep the scraper from buckling under the force.

Holding the scraper up to a raking light will show any remaining irregularities. The first time you joint your scraper you may need to take a few more strokes that later on when you are just maintaining the edge.

I should also mention that your scraper has many edges to work with. There are four sides on each of the back and front of your scraper. Add them up and you could use as many as eight edges. I find this takes too long, and I have a problem cutting myself on the sharpened burrs. I usually pick one long side and, through the method contained here, I get two sharp edges. If I’m digging into a corner a may sharpen one short side, but I prefer to work with one side only. It takes less time to sharpen and, if done correctly, the edge lasts longer than you might think.

Once you are satisfied that the edge(s) are straight and square to the face, it’s time to hone. I place a drop or two of oil on my small Arkansas stone and insert it into the jig just as I did with the file. Firm downward pressure applied with the index finger should be enough to keep the stone locked in the groove atop the wooden jig. The edge is honed with the same motion as you used when jointing. Sometimes I flip or turn the stone in the jig to keep from wearing a groove in it. However, as I only use my stone on scrapers, the groove would probably not affect its performance. You’ll know when you’re done because the stone no longer drags against the edge.

When the edge is honed, remove the scraper from the vise, lay it down on the bench and hone the face. You need to remove any traces of the old burr, and any that may have been raised during filing. You don’t need to use many strokes and you should let the stone hang over the edge so your effort is concentrated right around the corner. And don’t forget to flip the scraper and hone the other side.

At this point you could quit and move on to step three. However, I prefer to take my strop, a piece of poplar with leather glued on one side, and strop the edge and faces of the scraper. This isn’t strictly necessary, but the smoother the metal is, the sharper the burr will be. I find it makes the tool last longer before re-sharpening too. As with the other steps, I make sure that the strop is held perpendicular to the face when stropping the edge but I don’t bother using the jig. Both sides should be stropped as well.

Before burnishing, you will have to reinstall the scraper in the vise. Make sure it protrudes enough so the burnisher doesn’t contact the jaws in use. Place a dab of oil on your finger and run it gently along the edge of the scraper. Holding the burnisher in two hands, make an even number of strokes back and forth along the scraper’s edge. Four to eight firm strokes (6 usually works for me) at 90° to the side will mushroom out the edge. Remember to keep the burnisher perpendicular to the scraper and don’t overdo it – less is more.

Some woodworkers advocate burnishing in one direction only and that’s fine if it works for them. That may be the way you end up burnishing too. I use both directions as I find that one direction gives me a more pronounced burr on one end of the edge than the other. After scraping the edge will leave ripples instead a flat, smooth surface. My burr is more uniform with back and forth strokes.

My experience has also been that anything over ten strokes will just give you a mess. Fewer passes over the edge yield a better burr, especially if they are firm, perpendicular and even. And don’t forget to oil the edge. If not, you will damage your burnisher.

I have one last comment about burnishers. They are available in different shapes – mine just happens to be teardrop shaped. I use the narrowest part of the teardrop to burnish. The less burnisher surface area that touches the edge, the more concentrated the force will be. This means you don’t have to press so hard to get the same effect.

Now it’s time to roll the edge. Even though you are working on one side of the rectangular scraper, you are going to get two edges so we are actually rolling two burrs. Refresh the oil on the edge with just a dab on your finger (you can just wipe the side of your nose if you want – it will yield enough oil), and pick up your burnisher. Holding it firmly in both hands, and at a five to ten degree angle to the horizontal, apply two firm strokes (forward and back) to the corner of the scraper. Again, less is more. Rotate the burnisher over to five to ten degrees on the other side of horizontal, and make two firm strokes on the other corner. Firm even strokes will form a beautiful burr on each corner of the scraper card. The hardest part of sharpening a scraper is keeping your burnishing strokes even and firm. A little practice and before long you will find this process as simply and fast as I do.

When your scraper starts making more sawdust that shavings, it needs to be refreshed. You don’t need to follow all of the previous steps every time your scraper stops performing. I typically re-burnish mine three to four times before going back to step one. I would not recommend honing without jointing the edge first. Simply repeating the burnishing process will renew your edge. When you find that re-burnishing is not helping, it’s back to step one to joint your scraper.

I like this system of sharpening because, after practice, I was able to complete all three steps and be back to work in under a minute. One trick I use to speed things along, especially when I am in the middle of a project, is to leave the scraper in the vise. Rather than remove the scraper for step two, I hone and strop it in place. As I said, I only put two out of eight possible burrs on mine so I don’t really need to hone that part of the scraper that’s covered by the jaws of my vise.

And that’s all there is to keeping your scraper sharp (he says a couple thousand words later). I have tried to be as detailed as possible but, after you try it, you’ll find there really isn’t too much to the process. Sharpening a scraper isn’t hard. Everyone says that. Getting the hang of it so you can sharpen it consistently is the difficult part. You shouldn’t have to spend much time sharpening these tools during use. It that were necessary, cabinetmakers would have pitched them into a ditch a long time ago. Cabinet scrapers are a tried and true woodworker’s tool and a great addition to your portfolio of finishing tools.

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Last updated December 1, 2006 • Site Map