Quick Tips – Questions & Answers

Concealing sapwood

Q: I have an attractive, wide piece of walnut that I would like to use for a small tabletop. However, it is marred by a streak of sapwood in one corner. Is there a way to conceal it without the repair looking worse than the problem?

A: The contrast between pale sapwood and darker heartwood is an issue with both walnut and cherry. With the prices for these furniture hardwoods so high, it doesn’t make economic sense to try and exclude all the sapwood from your project. One option is to use the sapwood thoughtfully, making it part of the design. The other is to disguise it. The good news is that there’s a quick, simple, and effective way to conceal sapwood. As with all finishing, you’ll need a sample board of the same species and ideally from the same board as the workpiece, on which you can experiment.

First, wipe the workpiece and the sample board with denatured alcohol. This will show what the wood will look like with a clear finish and how dark you need to dye the sapwood to make it blend in with the heartwood.

Next, mix up a dye that is close to the color of the alcohol-wetted heartwood. The most inexpensive dyes are powders that dissolve in water. Don’t use pigment stains, as these will muddy the appearance of the wood. Test the color on the sapwood of the sample board and, if necessary, tweak it. In this case, I used Lockwood’s walnut crystals for the dark brown color, but added a very small amount of rose pink to match the underlying tone in the heartwood.

If anything, err on the side of a sapwood that’s slightly darker than the heartwood rather than lighter, as the eye detects light areas more easily than darker ones. When the dye dries, it will appear much darker than the heartwood, but as soon as a clear finish is applied the two areas will blend into one and no one will know your secret.

The sapwood revealed. Wiping the surface with denatured alcohol reveals what the walnut’s dark heartwood and the pale sapwood will look like under a clear finish.

Find the color that matches. Test dyes on a piece of scrapwood until you find the perfect match. Be sure to keep the heartwood wet so you can see the true color you are trying to match. Then apply the dye, or combination of dyes, to the actual workpiece.

The sapwood concealed. When the dye dries, it will appear darker than the heartwood, but the two will blend together when a clear finish is applied.

Tips for working bamboo

Q: Attracted to bamboo as a renewable resource, I decided to make a small table using bamboo flooring. I installed new blades in my planer and removed the ridges on the back of the 4-in.-wide strips and the finish layer on the front. I knew that bamboo is loaded with silicates, but was shocked at the condition of the blades after planing about 1⁄8 in. off of about 50 linear feet. After cutting the legs on the tablesaw, I tried to handplane the slight mismatches on the glued-up leg joints. I used very sharp blades at a high angle but still got extensive tearout. Scrapers worked but became dull so fast that they were not a realistic option either. Do you have any tips on how to work this green but gnarly material?

A: I’VE WORKED WITH SOLID-CORE BAMBOO PLYWOOD and with sheets of bamboo veneer. I stack the former to get thicker pieces or, for thinner ones, resaw it on the tablesaw and bring it to finished size using a wide belt sander. I do not recommend putting pieces through a thickness planer, as you will get tearout regardless of feed direction.

For joinery, I’ve used dowels, biscuits, and slip tenons. When using through-tenons, I make them from bamboo. I use Titebond Original for laminating and assembling. I treat bamboo veneer like any other veneer, cutting and taping it to obtain the right size, and using Unibond 800 glue in a vacuum bag to apply the veneer. When trimming veneers, I use a standard carbide-tipped, flush-trimming router bit. I prefer to climb cut, which minimizes the splintering.
In short, carbide works well on bamboo but steel planer blades don’t, and sanding is the best way to get surfaces with no tearout.

Bamboo for you. You can purchase bamboo as paper-backed veneer, in various forms of plywood where bamboo forms the core and the faces, and as laminated slabs.

Hard but smooth. Bamboo is almost impossible to plane either by hand or machine, but it cuts very cleanly with carbide.

Cutting multi-sided shapes on the tablesaw

Q: I would like to cut a 9-in.-wide octagon on the tablesaw. How can I do this safely?

A: FOR A 9-IN. OCTAGON, start with a blank that is 9 in. square. For the jig, begin with a plywood base 3⁄4 in. thick by at least 9 in. long. To determine the width, multiply the side of a square by 1.41 (in this case, 9 × 1.41 = 12.69 in.). Subtract the 9-in. width from 12.69 in., and you get 3.69 in. This is the sum of two opposite corners of the square blank that will be removed to create an octagon. Divide 3.69 by 2 to get 1.84. Add 1.84 to 9, and the result is 10.84 or a hair less than 10 and 7⁄8 in. This is the width of the jig and the distance from the fence to the sawblade.

Cut a pair of 45° triangles. Attach them to the jig as shown in the drawing. Use a backsaw to open a sawkerf gap where the two points touch. Place the blank in the jig, and cut off a corner of the workpiece. Turn the workpiece 90º and repeat three times to leave a perfect octagon.

Cutting the octagon. The first cut and the second are made with the opposite 90º corner fully nested in the jig. Before the third cut and the fourth cut, the opposite corner is already cut, so the workpiece doesn’t reach fully into the jig.