I have pretty much followed through on my plan for the radius dishes. I had enough scrap ply left from the shop cabinets to build the jig that I used to cut the plates. There are a couple of things that I should mention up front. It makes an unholy mess of MDF dust. Wear a respirator. If I were making these dishes for a living, I would have figured out some method of dust collection, but for the two-off that that I'm making, I assumed clean up would be easier than rigging some elaborate method of dust collection.
Pictured, you can see the Xmas Tree Stand that serves as the base, the two end pieces to the right, the two rails for the router on the left, and the two sides on the foreground. The 1/4 inch MDF attached to the one side is a template for the radius that will be cut into the side piece. I have a nice one inch pattern bit that cuts such things like a champ and the template was an excuse to use it. Since we're not talking a ton of material that has to be removed, you could join the two side pieces together, scribe the arch, then remove the material with a belt or bench sander. Either way, it would work, but I recommend the investment in the bit.
Pictured, you can see the dish blank mounted on the Xmas Tree Stand. It's a rather simple affair. Use a wooden dowel. I used a 1/4 inch dowel. Your router bit is going to hit it, and you don't want to waste a router bit on this project. To make the blank, I did as described. I cut the MDF to size into two 22 inches squares. I then used a very simple circle jig. In a scrap of 1/4 MDF, I cut a hole large enough to accept a brass bearing on my router. The measurement is to the outside edge of the bit -- in this case a 1/4 inch spiral upcut -- and I marked the location on the MDF for a 21 inch circle (10 and 1/2 inches from the edge of the bit). I drove a finish nail through the MDF at the radius mark into the center of the dish, and viola! A circle cutting jig. It's pictured in my previous post. I cut the circle in the MDF to a depth of about 1/4 inch, then used my jig saw to cut the majority of the scrap away. On the router table, I finished the edges of the blank using my pattern bit running the bearing against the circle cut with the router. Since MDF chips easily, I rounded over the bottom of the dish with a 1/4 round over bit.
Pictured, you can see the router channel assembled. It didn't work exactly as I had imagined. With classic engineering oversight, on the length of the box, I had taken into account the width of the of the router base in determining the long end of the box, and so cut it only 3 and 3/4 inches longer than the 11 inch radius. I didn't take into account the handles on my router base. Also, I profiled the radius only on the long end of the box to the center marker. In another well-duh! moment, I messed up the measurements on the first go round and didn't take into account the off-set of the long end. I cut the radius from the center line of the side, not the center-line of the Xmas Tree Stand. I disassembled, trimmed it off and started over, but you can easily see that you would want the center line over the center of the dish not the side and the 1/4 deflection (or 1/8th) should be at the edge of the dish not the end of the side.
Here you can see the whole set up put together and ready to rout. Again, it makes an unholy mess of MDF dust, so use a respirator or something to protect your lungs. On the router, I used a 3/4 inch straight bit. The router wants to throw and spin the dish for you, but I could easily hold the router, hold and control the dish, and slowly advance the router from the outside to the center while turning the dish. The rubber pads on the clamps helped with that. I lightly pushed them against the dish and that too helped against the tendency to spin. I had thought of taking the handles off the router to make it fit the channel better, but thought better of it, and was glad I didn't.
When the dish comes out of the jig, you'll want to sand down the ridge on the edge and take away the router marks. But it worked, and I now have two radius dishes, one for the back and the other for the soundboard. The stuff in the jar is a mixture of titebond glue and water at about 50/50 mix. It's mostly just glue from nearly empty glue bottles. I rinse out the bottles and save the remnants. For lack of a better term, I call it sizing and I use it to harden MDF for sanding and just generally. I'll also put a coat of poly on them.
Pictured, you can see the dish blank mounted on the Xmas Tree Stand. It's a rather simple affair. Use a wooden dowel. I used a 1/4 inch dowel. Your router bit is going to hit it, and you don't want to waste a router bit on this project. To make the blank, I did as described. I cut the MDF to size into two 22 inches squares. I then used a very simple circle jig. In a scrap of 1/4 MDF, I cut a hole large enough to accept a brass bearing on my router. The measurement is to the outside edge of the bit -- in this case a 1/4 inch spiral upcut -- and I marked the location on the MDF for a 21 inch circle (10 and 1/2 inches from the edge of the bit). I drove a finish nail through the MDF at the radius mark into the center of the dish, and viola! A circle cutting jig. It's pictured in my previous post. I cut the circle in the MDF to a depth of about 1/4 inch, then used my jig saw to cut the majority of the scrap away. On the router table, I finished the edges of the blank using my pattern bit running the bearing against the circle cut with the router. Since MDF chips easily, I rounded over the bottom of the dish with a 1/4 round over bit.
Pictured, you can see the router channel assembled. It didn't work exactly as I had imagined. With classic engineering oversight, on the length of the box, I had taken into account the width of the of the router base in determining the long end of the box, and so cut it only 3 and 3/4 inches longer than the 11 inch radius. I didn't take into account the handles on my router base. Also, I profiled the radius only on the long end of the box to the center marker. In another well-duh! moment, I messed up the measurements on the first go round and didn't take into account the off-set of the long end. I cut the radius from the center line of the side, not the center-line of the Xmas Tree Stand. I disassembled, trimmed it off and started over, but you can easily see that you would want the center line over the center of the dish not the side and the 1/4 deflection (or 1/8th) should be at the edge of the dish not the end of the side.
No comments:
Post a Comment