Today, I bit the bullet and tried out my 45 degree lock-miter bit to make the four-sided quarter-sawn white oak 4” x 4” legs. I outsmarted myself by trimming the edges at 45 degrees. Unbeknownst to me, the router bit needs all the meat it can grab to make the “tongues”. As a result, I have very little “lock” in my lock-miter. I have just enough to register the corner, but I’ve lost about half of my glue surface. Sigh… The good news is that the remaining half should be more than strong enough once it’s glued together. This concerns me a bit because that’s a lot of wood to take out in one pass with a large diameter bit. You have to take it out in one pass because you can’t mess with the horizontal/vertical alignment once it’s setup. This means the bit would have to take square stock and make it 45 degrees, plus and minus the tongue & groove parts. I had enough problem pushing it through safely with the featherboard and router bit spinning.
The large diameter bit is rather scary to use. I dialed my router speed way down. I used a featherboard to help secure the work, which allowed me to focus on downward pressure. I also found out that there’s a small shoulder of the edge left, which means the outfeed side of the table can be flush with the infeed side. I was worried because my test pieces had a bit of the edge removed, which caused the work to rock as I passed it across the router table. BTW, my router table is an extension of my table saw, so I can use my Biesemeyer fence with an MDF adapter to act as a relatively accurate (and space-saving) router table. The blade guard is a bit in the way, but I’m willing to deal with the inconvenience.
BTW, I used the following method to “center” the lock-miter bit. First, I set the height by passing two pieces of identical thickness running flat horizontally. When mated, yin-yang style, they should fit flush if the router bit is the right height. I had to make a couple of adjustments which is tough, since my router doesn’t have a lift. The flip side is to adjust the fence depth. This is done the same way, with test pieces run vertically up against the fence. If the pieces fit flush, then your depth is correct. There are shortcuts to this method, using two parts, one part, labeling, etc. but the end result is two parts the same thickness as your final piece should fit flush both horizontally and vertically. Sorry if this is confusing in written format, but it’s relatively obvious when you’re actually doing it.
I routed the vertical side on one edge of every piece and the horizontal edge on the other so that there would be no possiblilty of me mucking it up. This also has the additional benefit of guaranteeing that the columns are square. I can’t believe how much air there is inside the leg! That right there caused me to break even on the lock-miter bit. This also should make the mortises easier, since I don’t have the extra 2-1/2” of meat to chisel through.
While sighting down the legs after they’ve been dry fit, they’re not intersecting at the corners as perfectly as I’d like, but they are consistent down the length of the leg. I plan on easing the edges with a small radius round-over bit, which should cause the seam to disappear in the grain. I’m going to use sticks in the middle of each 4” face and wrap that rascal with stiff bungee cord to act as a clamp to force the lock-miter together. I’ll probably do one leg at a time so I can use my limited number of C-clamps to assist the process.
The dry-fit leg is standing next to the new table top in the dining room and looks incredibly beefy. In fact, it’s so beefy that I could probably address my missing tongue issue if needed. I wanted a 4” x 4” leg to balance the large breadboard ends. I think I’ve achieved my goal. Now if I can just glue these damn things up…
-- You can't control the wind, but you can trim your sails