Sew-It-Yourself Home Accessories. Scott Wynn
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in the block can change the angle of the wedge cut, preventing the wedge from fully tightening. You must then refit the wedge by careful trimming of (usually) the top of the wedge ears to exactly fit the block. This will lower the wedge a bit, which may require trimming the ends of the ears, and in a worse case, some refitting of the wedge to the chipbreaker. This usually doesn’t happen a lot in the life of the plane, especially if the block was dry when it was made and is oriented bark-side-down and quartersawn (or nearly so), but it’s something to keep your eye out for.
The use of a cross pin for bearing the wedge against is a solution that avoids the labor-intensive need to exactly cut the abutments and fit the wedge to them. But you won’t find this solution on any old planes. It starts showing up in early metal transition planes, but I don’t think I’ve seen it on an old wood plane. I think the reluctance to use a cross pin was because until the late 1800s drilling technology could not be counted on (at least in woodworking) to give an accurate and reliably-sized hole—and tradition imparts a certain inertia to changing a solution that has worked for centuries anyway.
A metal cross pin can be used when it bears against metal, such as on a Japanese plane where it bears on the chipbreaker (though it only holds the position of the chipbreaker and not the blade), and on some versions of Chinese planes where the chipbreaker doubles as a metal wedge; but a metal cross pin bearing against a wood wedge will soon damage the wedge, indenting it enough that adjustment becomes difficult. A wood cross pin can be used with a wood wedge, but the difficulty with a cross pin in general is its greatly reduced cross section often doesn’t provide enough resistance to keep the wedge from loosening when the plane is being used. A common response is to drive the wedge in tighter, but eventually this will damage the block, bend or break the pin, or leave an indentation on the wedge that makes adjustment difficult. German manufacturers solved these issues by using a metal cross pin with a wide flattened surface to grip the wedge, coupled with large diameter fixtures to which the cross pin is fixed to the block (See Figure 1-4). These cross pin mounting fixtures greatly increase the bearing area of the pin to the block, reducing the chance that an over-driven wedge will damage the block. An additional advantage to the system is that you can push or tap the wedge sideways to loosen it, rather than beating on the plane to loosen it. From personal experience this is a very successful solution to the wedge.
Figure 1-4. You can see the flattened cross pin under the wedge of this horned scrub plane.
James Krenov used a wooden cross pin to fix his blades, which he carved to a flat section where it engages the wedge to give it more bearing area. However, you have to glue the block up in sections in order to be able to insert it into the plane. What if you prefer—for a number of good reasons—to use a solid block? The solution is to add a wooden bearing plate to a wooden cross pin already drilled through the block (Figure 1-5). The wooden cross pin has a larger bearing area than a steel pin and is equal in hardness to the block, thus reducing stress and wear on the block, and the added bearing plate reduces the chance that the wedge will shift, and extends the pressure over a larger area of the wedge and blade, helping to reduce chatter. This is the system used in the planes described in the chapter “Making & Modifying Planes”see here.
Another wedging system in use is the screw-down lever cap (Figure 1-6). The lever cap is held to the plane with a screw inserted into the blade bed (rather than a cross pin), and much like the lever cap on a Stanley plane, the blade is adjusted by tapping, as with a wedge system. This can be a good system, and one that you might consider as a possible alternative for the cross pin/plate system used in Chapter 8. However, there are a couple things to look out for. First, the blade must be a parallel blade and not tapered. Second, because the blade will not move under full pressure, the lever cap cannot be tightened down fully until the blade is adjusted. However, because of the thinness of most modern blades and the curve of many chipbreakers over their length (to ensure tight contact with the blade), the chipbreaker/blade assembly is flexed to an arc when the chipbreaker is screwed to the blade.
Figure 1-5. Wooden cross pin with pressure fit bearing plate for fixing the wedge.
Tapping the blade to what appears to be its final position and then tightening down the lever cap flattens out the blade/ chipbreaker assembly, usually pushing the blade out of the throat slightly and changing the adjustment. You must then loosen the lever cap again, back the blade off, and second-guess how much the blade will move when the lever cap is tightened back down. This makes fine or frequent adjustments tedious. A thicker blade and/or a different chip breaker that keeps the assembly flat might remedy the situation.
Taking a quantum leap in development, a German manufacturer has replaced the wedge altogether with its Primus adjustment mechanism. The Primus blade-adjustment mechanism is one of the quickest and most precise adjustment systems. There is zero backlash on this adjuster. It can give precise adjustment on a smoothing plane, but I find it particularly useful on a jack plane, where frequent readjustment can be required to level a board; with this adjuster I can quickly and accurately readjust the blade as the board levels.
Its main drawback is its complexity. It is time-consuming to remove and replace the blade for sharpening, so frequent re-sharpening, as might be required for final finishing, is pure drudgery. To remove the blade for sharpening, first the blade-tensioning mechanism and blade adjustment must be backed off almost completely, and the blade withdrawn. Withdrawing the blade requires pushing the blade-tensioning mechanism back in and twisting and then pulling the tension rod out. Because the blade is now loose, it just flops around as you try to twist the T-bar on the end of the tension rod, because the T-bar gets wedged on the chipbreaker and must be worked off. Once the blade is out, two tight-fitting screws must be loosened to remove the chipbreaker (Figure 1-7).
After sharpening the blade, the chipbreaker must be repositioned and carefully tightened down with some trial and error (the use of another type of chipbreaker is not an option as both the blade-tensioning device and the lateral-adjustment mechanism are part of the chipbreaker assembly). Then you thread the T-bar on the end of the blade-tensioning screw through the hole in the chipbreaker, rotate it, push it forward, rotate again, and pull it back to its seat on the chipbreaker. This whole process of removing and reinstalling the blade can take 5 to 10 minutes (or seem like minutes). Doing it a lot gets to be quite irritating. Luckily, with its chrome-vanadium blade, if you are rough planing, you will not have to do it very often.
Over the years, other solutions to the wedge and how to adjust the blade have come about, especially with the German manufacturers, who are still one of the few manufacturers of traditional style wooden planes easily accessible to the American (and other) markets today. One type you might find is a version of the screw adjuster, with a knob similar to the Primus but working more like a Norris adjuster. It has the screw (a worm gear, actually) directly engaging threads on the chipbreaker. This version does not use a tension rod. Because the purpose of the tension rod is to eliminate backlash or play in the adjustment mechanism, this version does have some play, but it is not too bad and is a serviceable adjuster.
Figure 1-6. Horned Reform Smooth Plane with Screw-Down Lever Cap The body is pear with a lignum vitae sole. The body has had some extra rounding to accommodate the user’s hand.
Figure 1-7. The Interior of a Primus Jack Plane In the well of the plane