On the left, a traditional jack plane with its wedged blade, a system in use for centuries. On the right a modern German horned jack plane, with a spring-loaded screw adjustment mechanism for adjusting the blade.

       Figure 1-1. Wood Block Plane

THE BLADES

      Unlike today’s planes, up until the early 20th century wood-body planes from Europe and North America usually had a tapered blade, thicker where the cutting edge is and thinning toward the opposite end. The main reason given for this is that the natural wedging action of a tapered blade resists being pushed back under the load of cutting wood, and also makes it easier to remove, because you can tap the blade down and it will release quite quickly (often too quickly). But it also makes it harder to adjust: if you adjust the blade down too far you may have to completely loosen the wedge and blade and start over if you want to readjust the blade back up.

      I think the reasons usually given, such as this one, are the (questionable) side benefits of the method of manufacturing the blade. As we all know now—and they probably did then—parallel blades stay put just fine under the wedge. They are also easier to adjust because they do not lock in so tightly in one direction. You can move them down further than a fraction of an inch and not have to worry about them unexpectedly flying out of the mouth of the plane.

      Here is my theory for the taper. When making a laminated blade by hand, you have the extra thickness of the edge steel added to the backing steel blade blank, the two of which must be forge-welded together. Then you have to hammer the assembly until the backing steel flushes with the edge steel on the top of the blade. If you do not hammer out the blade at the edge end as well—it is easier not to—then you have begun giving the blade a taper. From there, you continue the taper just making sure the back of the blade is slightly concave along its length. This guarantees the blade will bed properly at the heel despite any irregularities along its length, or irregularities in the hand-cut bed. This also means you can reduce the amount of grinding on the back. I have blades that still have the hammer marks on the back (Figure 1-2). A parallel blade must be accurately ground on both faces, which cannot easily be done freehand. An added benefit is you have maximized the thickness of the blade near the edge, further reducing the chances of chattering in use, especially if a substantial chipbreaker is added.

      Modern versions of the traditional form have parallel blades and are only rarely laminated, though I do have a German scrub plane from the early 1980s that has a laminated blade. They were made and can be found (and laminated Japanese replacement blades for these planes are available), you just have to keep your eye out for them (for more on why you might want a laminated blade—and what it is, see the chapter on steel that starts here).

CHIPBREAKERS

      Woodworkers throughout the world had for millennia worked with the same somewhat narrow selection of indigenous woods, often a single species, or no more than two or three, within a trade. They knew how the wood reacted, which tools and their setup worked best for those species, and they had a good selection of material and better control of their sources. New Worlds, new prosperity, greater travel and print exposure, brought a higher level of sophistication to their customers, which brought a demand for new designs and a higher degree of finish in the work. Additionally, new and imported woods often brought new challenges to providing this higher degree of finish than the indigenous woods they had worked with for centuries. The use of a chipbreaker helped solve some of these problems. It made planing these new woods more reliable, so the work went faster and with better results (see Figure 1-1).

      Figure 1-2. If you look closely at this blade in the area of the chipbreaker screw, you can see the semicircular edges of the impressions left by the forging hammer.

CHIPBREAKER VARIATIONS

      British and American chipbreakers have a slight difference (which has no effect on performance): British chipbreakers often have a “nut” of which there are a number of variations, that is proud of the top surface of the chipbreaker into which the screw is threaded; with an American chipbreaker the screw flushes out with top surface of the chipbreaker. This sometimes results in very little thread for that screw, depending of the thickness of the chipbreaker, but I haven’t had one strip out yet. (More about chipbreakers in Chapter 3 here.)

      The chipbreaker is almost always screwed to the blade, unlike Japanese planes and some Chinese planes. I say almost always because I have a French smoother (smoothing plane) by Goldenberg that has a chipbreaker that is not screwed to the blade, but is adjusted independent of it. This is the only time I have ever seen this in a Western plane. This setup does increase the versatility of the plane because it makes it easier to adjust the chipbreaker up and down without having to disassemble the plane to unscrew the chipbreaker from the blade.

THE WEDGE

      The most common form for the wedge in antique planes is similar to that shown in the illustration (Figure 1-1) with the center portion of the wedge cut out for chip clearance and wedgeshaped “ears” at the edges that wedge into matching abutments cut into the block. The cutout may be done in different ways: it may have a circular shape or as frequently found in Chinese planes, it may be a simple V-shape cut. Or there may be no cutout at all, the wedge cut to thin taper at its lower edge, though this is usually found on modern planes using a cross pin (Figure 1-3). Besides giving added chip clearance, the use of the ears simplifies fitting the wedge to the top of the chipbreaker, which may be curved or otherwise irregular.

      Figure 1-3. The top two wedges are the most common type with “ears” that fit into tapered abutments either side of the plane, the center of the wedge relieved to a thin edge to clear chips. The third wedge from the top is from a French plane (with one of its ears slightly broken) and the bottom wedge is from a Chinese plane, though occasionally you might find similar wedges on European and American planes.

      The use of a wedge fitted into abutments cut into the block, besides being a nuisance to fit simultaneously to an irregular chipbreaker and the taper in the block—and it must be well fit to eliminate chatter and prevent blade shift under use—is that seasonal movement

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