A hand scraper is perhaps the simplest tool in any toolbox -- it is nothing more than a thin piece of hardened steel. In the hands of an experienced craftsman, however, the scraper can be used to produce a finish which far surpasses the finest sanding, both in terms of smoothness of surface and beauty of grain.
Unfortunately, scraping has developed somewhat of a mystique of being a difficult skill to master. While it is true that is somewhat more demanding than putting sandpaper in a block sander, it should not be beyond the capabilities of any woodworker. With proper preparation of the scraper and a little practice, even the most ham-handed "wood processor" should be able produce a finished surface that gets noticed.
This does not mean that a scraper is a panacea for all wood finishing.
Together with a plane, however, a scraper can reduce sanding to an absolute minimum. Although there is no general formula, the first tool for finishing is a finely tuned smoothing plane. In many cases, the finish produced by the cutting action of a sharp plane blade produces a better surface then a scraper. However, on some woods, even the best prepared smoothing plane can often not produce a defect free surface. Tropical woods and woods with wild or rowed grain often tearout with a plane. It is on these woods where the scraper excels. On soft woods, such as pines, where a scraper is ineffective, a plane will produce a glass like finish.
Look very closely at the surface after performing the scraping. Unless you are a master of the scraper, your best efforts may leave washboard marks or other streaks. These can be removed with a few light passes of a sanding block and 320 or 400 grit paper. The resulting surface will still retain the characteristics of a scraped surface since the abrasive action was only used lightly at the final stage.
As mentioned above, a scraped finish is often noticeably better than a sanded one. Typically, the grain on a scraped piece is very clean, and appears almost three-dimensional when finished. The feel of a scraped surface is also quite different -- it has none of the "fuzziness" that a sanded piece does. The differences between the sanding and scraping actions on a microscopic level are the reason.
GROSSLY simplified, sandpaper works by grinding down high spots on a surface, using its grits to scratch and break the wood fibers. If the scratches left by the sandpaper are small enough, the surface looks to be perfectly smooth. If one were to look at the resulting surface under a microscope, however, it would tell a different story. The fibers of the wood would be ragged and torn, and the pores would be filled with dust and grit from the sandpaper.
A scraper works by cutting action, much like a plane. This means that the wood fibers are cut, and not torn like they would be by sanding. The resulting surface will still look good at magnification, which translates to a beautiful finish.
In addition to the superior surface which results from the scraper there are other beneficial reasons to use this tool:
Hand scrapers are available in many different profiles, but the most commonly encountered are rectangular (normally about 10cm x 6cm) and gooseneck (shaped like a draftsman's french curve). These two shapes will handle 99% of scraping tasks, and are a good starting set for beginners. Since scrapers are quite inexpensive and last forever, it usually makes sense to buy the best available.
Scrapers are available in various thicknesses. Thicker scrapers are for heavy stock removal, and are analogous to the 60 or 80 grit type sandpaper. Thinner scrapers flex easier and are better for preparing a surface for a finish. Very thin scrapers are for fine finishing and for leveling the finish. These very thin scrapers can be used to cleanly level between finish applications without the clogging or scratch patterns that often results with a 400 or 600 grit sandpaper.
You have to look carefully through the various woodworking catalogs for the different thickness scrapers. Eberol is one company that makes various thicknesses. I suspect Sandvik also makes other then the common #474 and #475 ( .6 and .8 mm ) but are probably not stocked by the catalog companies. It is also possible to make a scraper from an old hand saw or bandsaw blade. In many rusty old saws the steel is good and will hold a burr.
A scraper works by virtue of a tiny sharp burr on its edge, formed by the burnishing process. This burr will slice the fibers of the wood like a tiny plane, with the face of the scraper acting as a chip breaker to eliminate tearout. The result will be ultra-fine shavings, even on pieces with difficult grain. Without the proper burr, the scraper will not have the desired cutting action -- it will just drag over the surface. Thus, an improperly burnished or dull scraper will produce dust instead of shavings, with a resulting decrease in surface quality. When this happens, it is time to reburnish or sharpen the scraper.
When using a rectangular scraper it is normal practice to prepare the front and back edges of the two long sides (4 edges total). With a curved scraper, only the section that matches the profile you are scraping needs to be prepared. Hold the scraper up to the piece and move it around until you find the matching bit of curve, then mark the area of contact on the scraper with a pencil. This will show the portion of the edge which needs to be prepared, and aid in aligning the scraper when used.
With any scraper, the preparation is a three part process:
These steps are always done in order, but many times it is not necessary to square or hone. A scraper can normally be burnished 5-6 times before it completely loses its edge and needs to be re-squared.
The first step in the preparation of any scraper is to make the edge perfectly flat and square. Any existing burr needs to be removed to allow a razor sharp edge to be put on. Squaring is done with a mill bastard file held perfectly perpendicular to the scraper face. The scraper should be held in a vice, and the file drawn along the edge 3 or 4 times-only a very little amount of material needs to be removed.
When squaring a rectangular scraper, it is very important that the edge be kept straight as well as square. For this reason, one will normally run the file lengthwise along the scraper. Keeping the file square is very difficult in this configuration, so some sort if jig is normally used. Fancy commercial jigs are available (which work quite well), but I have found the following simple jig to be the best (and cheapest) solution. It consists of a piece of 4/4 hardwood about 8" long and 2" high, with the following profile:
The file is held in the rabbet on the top of the piece, and should protrude well over the edge of the block. The face of the jig can then be held against the scraper face while filing, ensuring a perfectly square edge. Note that the corner where the scraper will contact the file has a small chamfer. The chamfer will provide clearance for any existing burr, as well as give filings a place to collect.
Squaring a curved scraper follows the same basic procedure, but can get a bit more complicated if the curve is concave. If the curve is convex, the same procedure (and jig) can be used as for the rectangular scraper. The only difference is that you need to follow the curvature of the edge as you file. If the curve is concave, however, the square file will not be able to make contact-a half-round file must be used. The file should be held across the edge of the scraper with one hand on each side, and run along the edge for 3 or 4 strokes. It is easier to hold the file level in this configuration, so a jig is normally not necessary.
After the scraper edge is perfectly square and without burr, the next step is to put a razor-sharp corners on each prepared edge. The honing is done just as you would for any cutting edge, only in the case of a scraper there is no bevel -- the edge is honed to a perfect 90 degree angle.
To obtain a sharp corner, both the edge and face of the scraper must be honed through a series of progressively finer grits. For each grit of stone, the faces are honed first, and then the edge. After honing the edge at the finest grit, you may opt to strop the sides to get a perfect edge.
Honing the faces of a scraper is quite simple. All that is required is to hold the scraper face flat on the stone while moving it in a circular motion. Care should be taken (especially on the soft waterstones) to use all areas of the stone, so as not to wear the face unevenly.
Honing the edge is trickier, since the scraper needs to be held perfectly perpendicular to the stone to keep the edge from being rounded over. Again, there are commercial jigs to solve this problem, but the squaring jig described above can be used for honing as well. To use this jig for honing, simply hold the scraper against the back of the jig, even with the bottom, while running the edge on the stone. This provides a large surface to run on the stone, thus keeping the scraper perpendicular at all times. I put a small chamfer along the back bottom edge of my jig, to give the some relief for the edge.
It is very important to run the scraper edge at a skew across the stone. If the edge is run parallel to the stone, it will very quickly form a rut in the stone's surface. This will not only produce a rounded edge on the scraper, but it will ruin the stone for normal sharpening as well. For best results, the scraper should be skewed as much as possible while still keeping the entire length of the edge on the stone.
The edges of curved scrapers can be honed in the same fashion as rectangular scrapers if the curve is convex. The only difference is that multiple passes will be necessary to hone all parts of the curve. Concave curves are more difficult (as usual) -- they must be honed "freehand" with a slipstone.
As a final touch, I like to use a rigid leather strop with jeweler's rouge. Place the face of the scraper on the strop and pull (don't push) to the edge. One or two passes like this on each edge will remove any honing burr and leave the edge incredibly sharp.
The final stage of scraper edge preparation is burnishing, where the tiny cutting hook is applied to the edge. This is the most critical part of the process, as even the sharpest scrapers will not work if they are not properly burnished.
Successful burnishing begins with the selection of a burnishing tool. Many things can be used as burnishers, and everyone has their own favorite, but they all should have similar characteristics. The burnisher should be a hardened high-carbon steel rod of some sort, and be long enough to allow significant pressure to be applied with it. The type of steel in the burnishing tool is critical-it must be harder than the steel in the scraper or it will not work. Since scrapers are normally made of a hardened tool steel (so they keep an edge longer), this means that the shaft of your favorite screwdriver or chisel will not make a good burnisher.
Commercial burnishers are usually made with carburized steel rod -- the same steel as used in bearings. These are a wide variety of burnishers sold, ranging from a simple rod with a handle all the way up to special gadgets that allow you to dial in the desired hook angle. The simple models are quite inexpensive, and work very well. Your favorite auto repair shop is another good place to find a burnisher-wrist pins and lifters both work very well, and used ones are often free for the asking.
Another crucial consideration for burnishers is the surface. The burnisher must be perfectly smooth -- if there are any irregularities in the surface of the burnisher, these will be transferred to the scraper, and thus to the scraped surface. The surface quality of the commercial burnishers vary. Veritas and Hock offer highly polished ones ready to use. Kunz requires honing and buffing to produce an acceptable surface. Steel from autos will normally require a similar preparation.
Burnishing a scraper is a two part process -- you first need to draw a burr from the edge, and then turn that burr back to make the hook.
To draw the burr, hold the scraper flat on the workbench with the edge about 1/4" from the end of the bench. Put a bead of light machine oil along the edge to keep the burnisher from galling. With the burnisher held slightly off level, make several passes with the burnisher along the face of the scraper at the edge. Even pressure (and lots of it) should be applied to the burnisher throughout the process.
This process should be repeated on all edges of the scraper. The end result of this phase will be a tiny burr on the edge of the scraper, as such:
Drawing a burr on the scraper edge has several effects. It makes a sharper point on the edge to aid the cutting action, and make it easier to turn back a hook. It also hardens the steel in the edge, making it cut longer.
This final step in the burnishing process is to turn the burr back to make the hook. To create the hook, hold the scraper in a vise with about 1" extended at the top (be sure to use wood blocks in the vise to prevent ruining any prepared edges). Again, run a bead of light machine oil along the edge to prevent galling. Holding the burnisher about 15 degrees off level, make several passes along the edge of the scraper. Once again, use heavy even pressure all along the stroke. Repeat this process with the burnisher tilted 15 degrees in the other direction to form the hook on the other side.
The end result of this phase will be a microscopic hook on both sides of the edge, as such:
At this point, the scraper is finally ready to be used!
Once the edge is properly prepared, using a hand scraper effectively is quite simple.
To use the scraper, hold it in two hands with one of the prepared edges resting on the piece to be scraped. If you are using a rectangular scraper, bow the scraper very slightly to prevent the edges from digging in (curved scrapers are not normally bowed, since bowing would change the shape of the curve). Tilt the scraper towards you about 20 degrees, and pull it towards you. The result should be a lacy shaving which crumbles when touched. If the scraper is just dragging along the surface, increase the angle a bit until it starts to pull up shavings. A bit of experimentation will be necessary at first to determine the optimum angle and amount of bow for scraping.
Alternatively, some woodworkers prefer tilting the scraper away from them and pushing, rather than tilting towards them and pulling. Either way will work-it is simply a matter of personal preference.
Best results can be achieved by scraping along the entire length of the piece, using multiple overlapping passes. Unlike planing, you need not pay close attention to the direction of the grain-a sharp scraper will work quite well against the grain. Cross and end grain scraping is also possible if you skew the scraper, but the results are usually not as good.
When the scraper stops pulling off shavings and starts making sawdust, it needs to have its edge burnished again. Each prepared edge of the scraper should be good for 10-30 passes (depending on the size of the surface and the wood) before it needs to be reburnished. When reburnishing, it is not necessary to draw the burr again-just turning the hook should be sufficient. Normally, an edge can be reburnished 4-5 times before it will no longer produce shavings. At this point the burr needs to be filed off, and the entire edge preparation redone.
(See also: Scraper Planes)
After using a scraper for a while, you will be come (painfully) aware of two problems with hand scraping -- cramped fingers and wrists from bowing the scraper, and burnt fingertips from the friction of the scraping process. These problems are not much trouble on smaller projects, but can become overwhelming if you need to scrape a kitchen-full of cabinet doors (this is the voice of experience speaking, folks). For these larger situations, a scraper holder is a necessity.
Scraper holders are simple jigs that hold a hand scraper (insulating your fingers from the heat), and allow a slight bow to be imparted (protecting your fingers from cramping). Commercial jigs are available (Veritas makes a very nice one), and shop-built scraper holders are easily made. The simplest scraper holder is a block of hardwood with screws/washers to hold the ends of the scraper in place, and a thumbscrew in the center to impart the bow.
The main drawback to using a scraper holder is the need to constantly remove the scraper and flip it over to use other edges. Most holders will only expose one (sometimes two) edges at once, so when the edge is spent the scraper needs to be removed and flipped to expose fresh edges. Since scraper edges wear out comparatively quickly, this can get to be a real pain. For this reason I only use a scraper holder when I have a great deal of scraping to do, and do most of my work freehand.
(See also: Scraper Holders)
Scraper planes are a special type of scraper holder which combine the flat sole and fixed cutting angle of a plane with the fine cutting action of a scraper. These planes require a specialized honing/burnishing process, due to the fact that the scraper edge is not square -- it is cut at a 45 degree angle.
Scraper planes share the same advantages as the simpler scraper holders, i.e. keeping your thumbs from burning/cramping, as well as the additional advantages of maintaining a constant cutting angle and preventing digging in the corner of the scraper. The angled cutting edge also allows a thinner, sharper hook to be turned, allowing the scraper to cut very aggressively.
Unfortunately, the disadvantage of the scraper planes over the scraper holder is even more pronounced -- there are only two sharpened edges on the scraper instead of four, and the edges are much shorter than on a normal hand scraper. This means resquaring is required much more often, with the corresponding loss in productive time. On the plus side, the thinner hook made possible by the angled edge usually lasts longer between burnishings.
Scraper planes come in three basic categories:
Each of these types is still in production (Stanley still produces the #80, Kunz makes a #80, #12 and #112 copy, and Lie Nielsen makes a very nice #212 copy), and there are also many of these available on the vintage tool market.
Edge preparation for a scraper plane is very similar to that of an ordinary rectangular hand scraper. It involves the same three steps of squaring, honing and burnishing, but each step must be done in a slightly different manner due to the fact that the end of the scraper is angled.
Click here for a description of the edge preparation process for hand scrapers)
The first major difference in edge preparations is how the edge is squared. A mill bastard file is still used to remove the burr, but now the end of the scraper is angled. To accurately file the edge, a jig is an absolute necessity. I use a variation of the simple jig described above, only with a 45 degree bevel where the scraper rests, as such (in profile):
As before, the file rests in the rabbet on the top, and the scraper rests against the front (beveled) face. I also like to cut a bit of relief where the file meets the scraper, to give the filings a place to collect.
Some woodworkers like to file one edge of their scraper plane slightly convex (new Stanley #80's come from the factory like this), in order to allow the scraper to take a deeper cut. If you wish to prepare an edge like this, it simply means that the squaring jig will have to move along the curve, just as for a curved hand scraper.
Another difference in the squaring of scraper planes is that a greater amount of material will typically need to be removed. The burr is normally much longer on the scraper plane, so it will take a bit more work to remove it. Also, it is very important that the file is only used on the edge -- DO NOT FILE THE SCRAPER FACE. It is tempting to save some preparation time by simply filing the burr flat to the face, but this will not leave the edge sharp enough to turn a decent burr.
Honing a scraper plane blade is also quite different. In most respects, the honing process for scraper planes is like that used for a plane iron or chisel -- both the back of the cutting edge and the bevel are honed through a progressively finer series of stones.
Just as with the square edge, it is very important that the edge is not rounded over-the squaring jig above can be used to maintain the proper angle, or one of the commercial chisel honing guides can be used. A microbevel is not needed (and actually may hurt performance) on a scraper plane.
Burnishing the scraper plane iron is actually simpler than the burnishing process for a hand scraper. Since the angled edge is already quite sharp, there is no reason to draw a burr-the edge can be turned immediately after honing.
Note that the burnishing angle for this type of scraper is measured AWAY from the face, rather than towards the face (as it is with hand scrapers). This means that the angle between the face of the iron and the burnisher should always be greater than 90 degrees, as such:
To turn the edge of a scraper plane iron, the iron should be held in a vice with the edge to be burnished up. Run a bead of light oil down the edge to prevent the burnisher from galling. Holding the burnisher at the desired angle, make several passes to turn the hook. Note that heavy pressure is not normally needed for scraper planes-the pointed edge typically deforms more easily.
Note that the angle of the burnishing is much more important for a scraper plane than for a hand scraper, especially on the models which do not allow you to adjust the angle of attack for iron (like the #80). A bit of experimentation will be necessary to determine the optimal hook angle you are comfortable with, but 15- 20 degrees is a good starting point. I use 15 degrees for my adjustable scraper, and slightly more for my non-adjustable.
The adjustment and tuning of the plane is the final step in preparation for use. To work properly, the blade must extend a very slight distance below the sole, and the edge must be perfectly parallel to the sole. If the iron is out of alignment it will gouge the workpiece, and if it is too deep it can chatter and leave a rough surface.
Adjustment of the iron is fairly simple -- all you need is a true flat surface (I use a piece of sheet glass) and a few pieces of paper. To begin, insert the iron into the plane so that its edge does not protrude beyond the sole of the plane. Set the sole of the plane on the flat surface, shimmed up by one or more sheets of paper, and move the iron down until the edge contacts the flat surface. When the entire edge is flat against the surface, tighten the blade retainer securely (being careful not to move the iron as you do).
On the #80 style plane, fine adjustments to the set can also be made by adjusting the thumbscrew which controls the bow of the scraper. Tightening this screw will advance the center of the cutter slightly. A very fine set can be accomplished by adjusting the blade even with the sole (i.e. no shims), and tightening the screw slightly.
If the plane has an adjustable angle, it should be set initially to the lowest allowable (i.e. farthest from vertical) and worked gradually towards vertical until it pulls off nice shavings. The actual ideal angle may vary for different kinds of wood or different burnishing angles, so it is best to test your setup on a scrap until you are happy with the results (be aware that the depth of cut needs to be adjusted every time you change the angle).
If the plane chatters during the cut, either reduce the cutting angle (if possible) or adjust the iron to take a shallower cut. When the plane stops pulling shavings and starts making sawdust, it needs to be reburnished. If reburnishing does not restore the cutting action, the edge needs to be filed off and rehoned.
While scrapers do not have a "sharp" edge in the sense that a chisel or plane iron do, they can still give you quite a cut if you are careless.
Safety around scrapers boils down to one very simple rule -- ALWAYS BE AWARE OF WHERE THE SHARPENED EDGES ARE AT ALL TIMES.
When preparing the scraper, be sure to keep your fingers clear of the edge. Burnishing is a particular danger since it uses a lot of pressure -- a slip here could result in a deep cut.
When using a scraper, be sure to keep fingers clear of the burr. Some people will only sharpen one side of a scraper for this reason (the other side's edges can be covered with masking tape to protect the fingers). Since I hate to sharpen more often than I need to, I use a slightly different solution-I cut a small piece from a plastic report cover spine, and use it to cover the edge I am not using. This works quite well for any rectangular hand scraper or scraper plane.
Always cover the edges of a scraper which is not in use. Some brands of hand scrapers come in plastic sheaths to protect the edge. These make very nice storage holders, or you can fashion your own out of a plastic report cover spine.
Best of Fine WoodWorking - Bench Tools, ISBN: 0-942391-84-5
Souped Up Scraper, pg. 64, Kelly Mehler (Best description of using a Stanley #80 I've seen.)
The Hand Scraper, pg. 66, Stephen Proctor
Fine WoodWorking on Hand Tools, ISBN: 0-918804-53-1
The Scraper, pg. 49, Tage Frid
Restoring, Tuning, & Using Classic WoodWorking Tools, ISBN: 0-8096-6670-X, Michel Dunbar,
Planecraft - Hand Planing by Modern Methods, ISBN: 0-918036-00-3, C.W. Hampton & E. Clifford
Chap 19, pp. 200-208
Hand Tools, Their Ways & Workings, ISBN: 0-393-01654-4
Aldren A Watson, Chap 26, pg 321-325
WoodWork, Vol #19 - Jan/Feb 1993
An Efficient Scraper, pg 74, James Gauntlett
The WoodWorker's Journal, V3#17 May/Jun 1993
Taming The Hand Scraper, Cover article, Roger Holmes