Sunday, January 31

Legs

This week we began a new project; a set of tray tables for Wanda. She wants hers to be all walnut, we also have a grandfather clock for Harold, also in walnut, and I’ll need walnut to work some more on the entertainment center in our living room. It’s been sitting half-done for 2 years, maybe I ought to get that completed. So, I started by hauling in from our lumber yard a whole bunch of rough sawn walnut lumber and standing it against a wall near the chop saw. I get out the template set for these tables, check them to be sure they're all there and in good condition, then picked through the lumber looking for pieces that were best suited for each part, and cutting the boards down into parts blanks with the chop saw. As I roughed out the parts I stacked them on the workbench and placed the template on top of each stack to help me identify which parts each stack was to become. I’ll start with the legs. I use a machine called a jointer to flatten one wide face, and one edge of each leg blank. These blanks will each produce from 2 to 5 legs, I need sixteen for a full set of tables. Normally, the step after jointing a parts blank would be to surface plane it to finished thickness, but in this case I’m going to break with convention and move right on to the table saw where I will rip ONE leg piece off of the blank, edge joint the blank, rip another leg off, edge joint the blank again, and repeat until the blank is cut up into legs. Why? Because ripping a wide piece of wood into two or more narrow pieces releases tensions in the wood itself and releasing these can cause the wood to bow or twist. Jointing the fresh edge flattens it again as well as smoothing away the saw marks. This reduces the amount of bow or twist the finished legs will have. When I’m done I have 16 leg parts that are 1/8” oversize in cross section and about ½” too long. Now we move into the final milling and shaping phase. This starts with sending the set of legs through the surface planer to smooth the remaining two sides and (and this is important) make the legs square in cross-section. Diamond shaped legs will make things come out all screwey. At each thickness setting each leg goes through twice; once with one un-jointed face up, then turn it 90 degrees to do the second un-jointed face. By always keeping a jointed face down on the bed, all the corners will come out at 90 degrees because I jointed the first two face flat and at 90 degrees to one another. The final step in milling the leg parts is to trim them to exact length. I do this on the chop saw, a.k.a. compound miter saw, equipped with a stop block to set the length so all legs come out the same. We start to make actual legs out of the leg parts by using my templates to lay out where each of the screw holes that will hold the base together will go and boring screw holes and countersinks or counterbores with the drill press I use a combination bit that drill the shank hole and the countersink/bore at the same time. The difference between a countersink and a counterbore is the depth. So by watching my depth I can perform all three functions with the one bit. The templates also allowed me to trace the shape of the upper and lower ends of the legs onto the leg blank, so I use a stationary belt sander to shape the parts. I use a crepe abrasive cleaner stick frequently to keep the sanding belt from loading up and causing the wood to burn. Then it’s back to the work bench where I use a random orbit sander to smooth all faces of the legs. This is construction sanding, using 100 grit paper. Finish sanding will be done later. The orange hose pulls the sanding dust away to keep it out of my lungs where it will cause emphysema which generally proves lethal. When the sanding is done I pre-finish the areas of the legs that will be inside pivot joints. And assemble the leg pairs at the main pivot. Getting finish in the joint after the table is built will be difficult, and not getting the job done will mean raw wood can show through when the legs are in some positions. This just insures everything looks good when I’m done. The second part of the base is the spreaders, which – as the name implies – spread and brace the legs. Doing these right is essential if the table will stand true and even without annoying clunking sounds as you close up the table. I start by jointing one wide face and one edge of each spreader blank. To do the edge I run the just jointed face against the fence to insure a 90° angle where they meet. In this case, a perfect edge is not essential as I will be rounding the edges anyway, but in most cases it is, so I use the same practices anyway. I run these blanks through the surface planer, jointed face down, multiple times to smooth the rough face and reduce the part’s thickness to the required ½”. Then the parts go to the table saw where I set up my precision miter fence. I trim a little off each end of the blank with the jointed edge against the fence to insure that both ends are good and square. These spreaders will determine the positioning of the legs and could induce unwanted bends if they were not square. Then I get out one of the most clever templates I have built; it does multiple things, as you will see. To start, it slips over the jointed edge of the spreader blank and allows me to trace the curve of the arches. The lower spreader is shaped like a bow tie with an arch on upper and lower edges. The upper spreader has an arch only on the lower edge, the top edge becomes part of the latching mechanism, and this jig lays that out for me as well by taping a nail through the two holes in the template. Then we go to the band saw and remove most of the waste wood from the arches by cutting just outside the lines. I could try to cut on the line and sand away any imperfections, but I have found a better and faster way. I put the spreader back in my clever template which has arms to grab and position it, chuck a flush trim bit into the router table and set the depth so the bearing on the bit rides on the template. In this way the template not only guides my pencil when I trace the shape, but also the router bit to cut away the last 1/16” or so of wood, leaving a smooth, perfectly shaped arch. Pretty cool, huh? Then it’s on to the drill press to make the oval shaped hole or slot that will allow the latch to hold the table open when it’s set up for use. I’m trying something new here – our camera has a video mode to take short video clips. Feel free to drop me an e-mail and let me know if you like or dislike this feature. Hmm... Blogger does not allow me to position the video clip like I do a picture, so I have no idea where that will end up, I'll use a picture here instead. The video may end up at the end. Then it’s back to the router table, swap out the bits for a round-over bit and round off all edges, except for the ends of course!. Now comes the tedious part – sanding. I can do the wide faces with the random orbit sander, but all these rounded edges have to be sanded by hand. This takes some time to do it right, so you might want to grab a soda or coffee out of the break room. One last thing this clever template does is to locate the pilot holes into which the screws that pass through the legs will go. These have to be perfectly placed or some very strange things will happen. I mark only one spreader with the template, then use that to set up a jig on the drill press. Once that jig is clamped firmly in position all the spreaders can be drill with the same setup. Here I’ll show you how it works. Or, maybe not. Again, I'm not sure where the video clip will end up. Finally, I assemble the legs and spreaders to for the bases. I do not use glue at this stage, just screws, nor do I plug the screw holes. It is possible adjustments will be needed later on. And that completes this step, now we will move on to making the tray panels. That will be done in a separate post. See you there! Time to publish this one and see what it ends up looking like.
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