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AW Extra 8/29/13 - Sawtooth Desk

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Sawtooth Desk

Create awesome patterns with a spindle sander.

By Lisa Clements


When most of my friends want something—like a new phone or a computer desk—they just ask their parents for it. I’m a little different, because I’ve been woodworking with my Dad for about eight years; when I want something, my dad and I make it. He’s taught me how to use all of the machinery in his shop and we’ve built many projects together. When I told him that I wanted to build a computer desk, we sketched a few ideas to work out the dimensions and then headed to the shop.

We get design ideas by experimenting. That’s how we came up with the desk’s sculpted legs. We were using the oscillating spindle sander to shape some rounded cutouts on a scrap-wood leg when we decided to see what happened if we tilted the sander’s table. Wow! Pushing the leg directly into the spindle created a really cool cone shape. Before long we discovered how to combine multiple cone shapes to create an intricate overlapping pattern that looked like a serrated sawtooth. Next came the idea to face a pair of mirror-image patterns. Separating them with ginormous loose tenons in a contrasting wood was the last piece of the puzzle. Awesome! We’d developed a simple process that gave our desk a signature feature.

 

Wood and big machines

The desk’s legs, rails and top are made of 8/4 Spanish cedar boards that were left over from one of my Dad’s projects. I like working with Spanish cedar because it doesn’t weigh a ton! It also sands easily, smells good and looks pretty. We decided to use wenge for the exposed tenons because its dark color would accentuate the overlapping curves we’d be sanding into the legs. Wenge looks awesome, but it’s no fun to work with because it’s hard and super splintery.

We used two of my favorite tools to make this desk. In addition to the big oscillating spindle sander, we used our Multi-Router to cut the mortises (see Sources, below). Dad says it’s unusual for a small shop like ours to have these tools. I say we’re lucky!

We started by milling lumber for the top, legs (including a test leg) and rails (A, B and C, Fig. A, and Cutting List, below). We chose the best-looking boards to make the top and the “next-best” to make the legs. Dad said to use the ugliest board (or even off cuts from the top and legs) to make the rails, because they wouldn’t show. I used ugly wood to make the test leg blank, too. We cut all the boards a couple of inches longer than the final dimensions and set aside the ones we’d chosen for the top and the rails.

We were fortunate to have wide boards, so our leg blanks didn’t have to be glued up. We squared the ends of the leg blanks at 28" and jointed their edges smooth while cutting them to their final 8" width.

 

Set up the sander

I installed a 4" spindle with a 60-grit sleeve in the oscillating spindle sander while Dad assembled the 3/4" plywood fixture that supports the leg blanks. Its 12" x 25" base and 6" x 60" support rail are fastened together to create one flush edge. Dad squared the fixture to the spindle and held it in position (butted against the spindle) while I clamped it to the table. Then I tilted the table to 45° (Photo 1).

I marked both sides of the spindle on the fixture’s rail and extended the two marks onto the edge that faces the drum (Photo 2). Meanwhile, Dad marked a reference line on the edge of each leg blank, 3" from one end. I placed the test blank on the fixture, squared it and aligned its reference line with the right diameter mark. Then I drew a third line on the rail (Photo 3).

I completed the setup by fastening the fixture’s 1-1/2" x 3" x 11" fence at this line (Photo 4). A 3/4" x 3" square block fastened to one end of the fence automatically positions it.

 

Shape the first profile

Dad turned on the sander while I held the test leg blank on the fixture with its end against the fence. Then I slowly but firmly pushed the blank straight up into the spindle (Photo 5). The spindle’s counter-clockwise rotation helped hold the blank against the fence. I kept pushing the blank until the sanded profile touched the mark (Photo 6). Then I removed the blank so we could check our setup by measuring the cone-shaped cutout on its edge, which we knew from earlier experiments should be 4" long at the bottom (the diameter of the drum) and 1-7/8" long at the top.

The cutout’s length at the top edge is important because it determines the overall length of the overlapping pattern. (You’ll learn why it’s the determinant in the next step.) When Dad and I were experimenting earlier, we learned that every 1° variance from 45° in the table’s tilt adds (or subtracts) about 1" to the pattern’s overall length, and this can cause problems with centering the overall pattern when you cut the legs to final length.

Tip: If the length at the top is greater than 1-7/8", it means the table is tilted less than 45° and needs to be adjusted.

Our measurements showed our setup was good, and that meant I could shape the first profile on the four real legs. So I did.

 

Shape on!

When the setup is correct, the large cutout on the blank’s bottom face is a semi-circle with a 4" diameter. I used its apex to draw a pair of reference lines, one on the bottom face and another on the opposite face (Photo 7). I used these lines as depth gauges to check all the remaining cutouts.

Next, I marked another reference line on the edge of the board, exactly 4" from the end of the 1-7/8" long cutout on the top edge (Photo 8). My Dad removed the fence from the fixture. Then we flipped over the blank and used its new reference line to reposition the fence and install it (Photo 9).

We were finally ready to shape the second profile—and create the first overlap. Dad turned on the sander aft er I’d positioned the test blank on the fixture with its large cutout facing up and its end planted against the fence. Then, like before, I slowly pushed it up into the spindle (Photo 10). Keeping the blank against the fence was harder this time, because the spindle’s rotation tried to pull it away. When the sanded profile reached the reference line on the edge, it also reached the depth gauge line on the opposite face (Photo 11). After verifying the profile’s dimensions and depth, we marked and shaped the second profile on the four real legs.

From here on, we just repeated the process to complete the overall profile: I marked the test blank 4" from the most recent 1-7/8" cutout, used it to reposition the fence, and then shaped the next cutout. Aft er verifying the profile, I shaped that profile on the real legs. There are seven overlapping profiles in all.

Tip: If you just can’t get the top cutout to measure 1-7/8", don’t use it to locate the overlapping profiles. Instead, draw the seven reference marks dimensioned in Fig. B (below) on the edge of your blank and use them to position the leg on the fixture. Using this alternate method will keep the overall profile at its intended length.

 

Match the legs

The next step was to align the overall profiles on each pair of legs and mark their final lengths by measuring from the center (Photo 12). I also marked each pair, so they’d stay together. Th en I cut the legs to final length. After that, I cut a centered notch in the top of each leg using a bandsaw with a fence. I carefully fit the width of the centered notches so the rail blanks slid in snugly, without binding or wobbling. I started by cutting just inside my layout lines and removing most of the waste. Next, Dad squared the bottoms using a coping saw. Th en I went back to the bandsaw and trimmed the shoulders by making tiny fence adjustments and testing the fit.

 

Rout the mortises

You may be thinking that we should have cut the mortises for the loose tenons before shaping the edges of the legs. Th at would have been necessary if we were planning to cut them with a plunge router or a Forstner bit mounted in a drill press. But as I said, Dad has this sweet tool called a Multi-Router, a joint-making machine that he uses constantly.

Unlike a plunge router, which would have to sit on the edge of the leg, the Multi-Router stations the leg on a table. And rather than plunging the bit into the wood, the Multi-Router moves the leg into the bit. So, by using the Multi-Router, it doesn’t matter that the leg’s straight edge has been sanded away. Besides, Dad says shaping the legs first makes mortising easier, because the bit doesn’t have to plunge 2-1/2" deep into solid wood.

We started by laying out the mortises, which we centered on two of the small cutouts in the outside face of each pair of legs (Fig. C). Th en we used the test leg to set up the Multi- Router. First we centered the bit on the edge of the leg. After installing the 4" long end mill, we set the table’s plunge depth and its side-to-side travel. Then we centered the bit on the edge of the leg. Once we’d dialed in the setup, cutting the mortises was easy (Photo 13).

 

Assemble the legs

Dad milled a wenge board to fit the 1/2" wide mortises and rounded the edges on the router table, using a bullnose bit. Then I crosscut the board to make the four giant loose tenons (D).

I applied glue inside the mortises in each pair of legs, inserted the tenons and clamped together the assembly (Photo 14). After making sure the assembly was square I washed off all the squeezed-out glue.

Dad said the two leg assemblies should be identical, so when they were both dry, I unclamped them and put them together. They didn’t quite match, so Dad trued them up with a hand plane. Then he had me finish-sand them. I hate sanding, but Dad says it’s one of the most important parts of building a project.

 

Glue up the base

I cut notches in the rails to fit the ones I’d cut earlier in the legs. Then I drilled countersunk screw holes for mounting the top to the rails and the rails to the legs. I also drilled pilot holes in the legs, so the screws wouldn’t split the end grain. Meanwhile, Dad widened the holes I’d drilled for mounting the top into slots to allow for seasonal movement.

We stood the legs on our super-flat assembly table to glue in the rails, so we could make sure everything was square. The only clamps we used for this glue-up were the screws we drove into the legs.

 

Make the top

I jointed the edges of the boards we’d chosen for the top and clamped them together with a single centered clamp to make sure the joints closed and the top would glue up flat. Then I glued the top together and washed off all the squeezed-out glue.

After the glue was dry I cut the top to its final width and length. Th e top was pretty big, so Dad helped while I routed its edges on the router table—we used a crown molding bit to create a concave profile that matched the cutouts on the legs (see Sources). This bit cuts a 2-1/4" long profile; we only used the top part of it, starting at the 45° chamfer. After that I was sentenced to finish-sand the top. At least it was flat—there weren’t a million cone shapes to sand!

 

Back to school

The base needed a little touch-up sanding, especially where I washed off the glue. The next step was to apply the finish, a job I always leave to my Dad, because he’s great with a spray gun. When the finish was dry, I attached the base to the top. Now to catch up on all that homework!

 

Cutting List

 

Fig. A: Exploded View

 

Fig. B: Mortise Locations

 

Fig. C: Reference Marks for Shaping

Click any image to view a larger image.

1. The legs are shaped using a simple fixture mounted on an oscillating spindle sander that’s outfitted with a 4" drum. Square the fixture to the spindle and then tilt the table to 45°.


2. Mark the diameter of the spindle on the face and edge of the fixture.


3. Mark a third line on the fixture using a blank marked 3" from one end. Align the mark with the fixture’s right diameter line. Make sure the edges are flush.


4. Fasten a 90° fence to the fixture at the line you’ve just marked.


5. Sand the first profile by sliding the leg blank up and into the sanding drum while holding the end firmly against the fence.


6. Stop sanding when the profile meets the line on the blank. Sanding the edge at 45° creates a cone-shaped profile.


7. Mark a line tangent to the apex of the deep cutout on the blank’s bottom face. Extend this line down the length of the blank, on both faces.


8. Mark the edge of the blank again, exactly 4" from the end of the shallow cutout on its top face.


9. Draw another line on the fixture with the blank positioned so that the shallow cutout and your second mark align with the fixture’s two diameter lines.


10. Install the fence at the line you’ve just drawn and then sand the second profile. As before, stop sanding when the profile reaches the mark on the leg.


11. The wide end of the second profile should be tangent to the line on the opposite face of the blank. Repeat the process shown in Photos 7 through 10 to complete each blank.


12. Mark the legs in pairs for cutting to final length. Butt the legs together and align their sanded profiles. Then measure from the center.


13. Cut mortises in all the legs for the loose tenons. The Multi- Router’s three-axis adjustability makes this easy.


14. Dry fit the legs and loose tenons to make sure the parts fit and the assembly is square.


Sources

Note: Product availability and prices are subject to change.

Grizzly, grizzly.com, 800-523-4777, Oscillating Spindle Sander, #G1071.

JDS Company, jdstools.com, 800-480-7269, Multi-Router; 1/2" dia. x 4" end mill, #12856.

Ace Tool Repair, Inc, acetoolonline.com, 877-783-8899, Freud Crown Molding Bit, #FRE-99-408.


This story originally appeared in American Woodworker April/May 2012, issue #159.