by Bill Lewis
The art of the handscraper, like that of French polishing and shrink-fitting is a disappearing one. I think it would be fair to say that not one cabinet maker in fifty can sharpen and use a cabinet scraper with real effectiveness. This is largely because of the development of power sanding techniques, the extensive use of plywood and the straight-line styles of modern furniture.
The handscraper is a very special "plane." It has the following unique characteristics:
1. It does not pull up the
grain, regardless of grain direction.
In general, the wood is thicknessed with a plane (which pulls up the grain somewhat) and then is smoothed with fine sandpaper, although sometimes a scraped surface is superior to a sanded one.
A scraper is used for levelling the mosaic to the top, for truing the purfling to the sides, top, and back, and for literally hundreds of small jobs which are often most difficuit to do any other way.
In the choosing of a handscraper, the quality of steel is very important. It must be malleable enough to burnish, but hard enough and tough enough to hold an edge. As with most other edge tools, I have found German scrapers to be the best for instrument making.
A handscraper is a flat steel blade sharpened in one of the two following ways:
Dive To Bottom
THE SHARPENING PROCEDURE FOR TYPE 1:
STEP I (TRUING)
Scraper is held in a vise and both sides are levelled and squared off with a file. Cross section must be rectangular and edges square.
STEP 2 (HONING)
In Step 2 (a & b), all three sides of the two corner cutting edges are honed on a stone (on both sides of the scraper: total of four cutting edges).
If you have trouble with wobbling in Step 2 (a), use a 2"x 2" wooden block as a guide to keep the blade at 90 degrees to the stone. Remember in Step 2 (b) to spread your fingers over the whole length (as shown in the diagram) so that the blade will be evenly honed.
Hold the scraper in a vise (with jaw guards). Lubricate the edge with oil or grease (lubrication is optional). With a burnisher, applying high pressure on the handle with one hand and on the tip with the other, move along the length of the scraper in the directions of figures (a) and (b) when burnishing the lower side of the blade. Several strokes are made this way (in both directions) with the angle gradually increasing from horizontal figure (a) to about 2 or 3 degree figure (c).
If you use too much angle on the burnisher (c), the scraper will seem easy to use, but will dull quickly and will not be reburnishable. That is, you will have to repeat Steps 1 and 2 each time you sharpen. Your burnishing will improve if you note carefully the direction of motion in figure (b) - always angle out slightly from the edge which you are burnishing.
The scraper can be re-sharpened a few times without Steps 1 and 2 by substituting the following process for those steps:
The above process is used on all four cutting corners so that the blade looks like this:
The scraper is now burnished very carefully, so as not to tear the fine tip, as in Step 3. Reburnishing is normally used only a few times, then the sharpening process is taken through beginning with Step 1 or Step 2. How many times you can reburnish is determined largely by how steep an angle is used in burnishing. The maestro could go for weeks on end without resharpening.
THE SHARPENING PROCEDURE FOR TYPE 2:
The Type 2 scraper often cuts somewhat faster and rougher than Type 1. It can often be reburnished more easily and more often than Type 1, but Type 1 has four cutting edges while Type 2 has only two.
With a file, the scraper is shaped as in the following:
With a stone, the scraper is honed much as in Type 1 but to the angles shown in the drawing.
Burnishing is done in much the same way as in Type 1, but again, note the following angles:
As always the burnisher's direction must be out from rather than into the scraper's cutting edge.
With a well-sharpened scraper, you should be able to remove a 1" wide shaving two or three feet long from a smooth piece of Brazilian rosewood. When you can cut like that, you've arrived - you are then a Qualified Handscraper Operator (medallion presented at the end of the line).
Scrapers can be held in many ways, but the most generally useful one is as follows:
As you become more and more familiar with handscrapers, you'll use them one-handed quite often, and at other times, with your thumbnail or fingernail as a guide, to clean up stains on purfling, etc.
Scrapers can also be used to flatten the surface of thick lacquer finishes. For this purpose, a very thin scraper is usually employed and is sharpened only to the end of Step 2 (not burnished). Sharpened in this way, the scraper will take an exceedingly fine, smooth cut. The lacquer is usually worked with the scraper from continuously varying angles in order to keep the surface flat. Afterward, it is cut with lubricated wet and dry (#600) sandpaper in preparation for rubbing out or buffing.
Scrapers sharpened in the above ways are also often used for cleaning up celluloid binding (and evening it with the top, back, and sides).
It is handy to have a few scrapers of different sizes, thicknesses, and shapes. These can be broken from standard size scrapers and ground to suit your requirements. The standard sizes are a must. A l"x 2" thin and a 1"x 2" thick (or 1-1/2" x 2-1/2") are handy sizes. Also, a scraper with a curved end and corner is sometimes handy.
Anyway, if you don't really know how to use a handscraper, learn. It is one of the best and one of the cheapest weapons in the instrument builder's arsenal.
Above is a photo of me scraping the purfling, on a Canadian cypress flamenco guitar, with a small scraper. What you can't see are the fingernails of the right hand sliding against the top and guiding the scraper along the purfling.
The photo above that is of Bernard thinning a piece of Brazilian rosewood. Study this picture carefully. Note the angle of attack from one hand to the other, which produces a shearing action. Also, note how the hands fold around the sides of the scraper rather than above it. Maestro Orti used to say, while holding two oversize, spatulate thumbs in the air, "The guitarero needs powerful thumbs - it's all in the thumbs." Scrape for a while and you'll see what he meant.
Varius Scraper Shapes
Text From The Luthiers' Mercantile Catalog - 1993
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