Tuning a Block Plane
Table saws, jointers, planers and other machines are vital tools in a furniture making shop. They get the job done more quickly than hand tools and with the potential for great accuracy. However, for some situations, like making a tenon fit a mortise, or making one surface flush to another, machines are often inadequate. They don’t have the finesse and fine-tuned accuracy of a hand tool. Two or three one-thousands of an inch can make quite a difference in fine work – this is where hand tools, and in particular, the hand plane, excel.
Hand planes need fine-tuning whether they’re antiques or brand new. After a few hours of remedial work, your hand plane will really sing. I say “sing” because for me, the sound of wood shavings peeling through the mouth of a sharp, well-tuned plane is truly music.
Let’s look at the steps to fine tuning a trustworthy friend, the block plane.
Flattening the sole
Bevelling the sole
Adjuster leveler cap
Blade after flattening
What Can it Do?
The block plane is a small plane that is typically held in one hand for light-duty use. Two-handed use is easier when using the plane for longer periods or when slicing through end grain. You can use it to trim the protruding tails and pins on through dovetails. It makes quick work of small chamfers and round-overs when the perfection of a router makes the piece look less “hand-made”. It is great for trimming one surface flush with another, whether it be solid wood edging, iron-on edge banding, or simply flushing off through dowel joints.
Less Work Than Larger Planes
Larger traditional planes such as smoothers, jack planes and jointing planes include chip breakers or cap irons. These must be properly fitted to the blade and smoothed over to promote good chip ejection. These planes also have a frog, which must be fine-tuned. Block planes, however, have no frog and no chip breaker. They are simple planes consisting of a body, a lever cap to hold the blade in place, a blade depth adjuster to move the blade in and out, and a gripping knob near the front. Some have a lateral adjust lever and an adjustable mouth.
The steps to tune-up a block plane:
• Deburring the casting and adjustable sole plate
• Flattening the sole
• Slightly bevelling the sole
• Improving the fit between lever cap and blade
• Flattening and sharpening the blade
The first step is simple. Remove the lever cap and blade and take off the adjustable sole plate, if any. Look for sharp metal burrs or paint that shouldn’t be there. Use a tiny mill file to remove these imperfections and clean up with some fine steel wool.
The adjustable sole plate, in particular, must be able to freely move in the channels ground into the sole. If there are any burrs or paint in the channels, then it will not move freely and the plate will not be flat with the rest of the sole when adjusted to different positions. Check the underside and edges of the sole plate as well.
Flattening the Sole
A flat sole is critical for any hand plane. Even more expensive planes can benefit from lapping. Sprinkle some 90 grit silicon carbide powder on a thick sheet of glass (I use ½“) and lubricate with kerosene. Make sure the adjustable sole plate is inserted and set to the position in which you will use it most.
The blade should also be in place and properly tensioned, though retracted so as not to grind the blade on the glass. Rub the sole around on the glass in random circles, figure-eight or back-and-forth motions until the entire sole is one dull gray colour.
Repeat the rubbing process with 180, 280, 400 and 600 grit silicone carbide powder. Make sure you clean any residue off the glass before switching from one grit to the next.
At the end of this process, you’ll have a flat and relatively smooth sole. Then take the plane apart, and with rags and a small brush, clean out all traces of kerosene and silicon carbide powder.
I often continue the rubbing sequence with waterstones, taking the sheen right up to 4000 grit or more. This produces a plane sole that significantly reduces friction when planing.
Bevelling the Sole
The sole will already have slight bevels ground around its perimeter by the manufacturer. Sometimes the bevels at the front and back of the sole are too small, leaving an almost-sharp edge. This edge may catch on raised areas when planing a surface, so I use a mill file to grind the edge down just a bit more. Push the file on an angle, working away from the sole instead of towards it.
Adjusting the Lever Cap
The leading edge of the lever cap sits on top of the blade, holding it into the body of the plane and preventing chatter. It should touch the blade tightly over the majority of its width. Since the lever cap is often painted on all sides, lumps of paint or minor burrs can prevent correct seating. Rubbing the leading edge of the lever cap on glass with silicon carbide powder can smooth things out.
You can use fine steel wool dipped in lacquer thinner first to remove the paint. If you prefer, you can flatten the metal with wet/dry silicon carbide sandpaper on a sheet of glass, instead of powder.
Flattening and Sharpening the Blade
Now you just need to flatten the back of the blade just as with your chisels. You can do this using silicon carbide powder on glass, or on your waterstones. You need to achieve flatness only over a tiny area directly behind the cutting edge. Then follow through with proper sharpening. (For more details on hollow-grinding and final honing, see “Waterstones” in Canadian Woodworking issue #36).
The true test is how the plane performs. A sharp, finely tuned block plane should be a joy to use, especially on more co-operative wood species such as Honduras mahogany, black walnut and European beech. Use a regular angle block plane for long-grain cutting and a low angle plane for end grain. End grain shavings are proof of a well tuned block plane, so enjoy the rewards!