John Schroeder
12-01-2009, 2:53 PM
So I have an Incra LS positioner, which is a very nice router fence. What I didn't factor in prior to purchase was the difficulty of dovetailing large upright pieces. Since I badly wanted to make a bookcase for our daughter with a dovetailed top, and I am too much of a newbie neander to risk cutting the dovetails by hand in birdseye maple, I set out to see if I could do it on the Incra router table.
Just to be clear: given the choice, I can't say I'd recommend the Incra as your preferred tool to make dovetailed casework. And although I think there is an Akida jig (and definitely an LN dovetail saw) in my future, the Incra is what I had to work with right now. Necessity is certainly the mother of invention, and it worked well enough that I though I'd share the relatively minor design changes I made to make it work for me. There are also a couple of other threads that touch on routing large upright pieces on an Incra (and the desire to see such a thing) so pics are attached!
The biggest issue was the right angle jig. I found the design to be subpar, and with an idea or two from some creative australians over at woodworkforums, I made a few improvements:
Replaced the plywood runners with longer UHMW ones. They provide more stability and greatly improve the sliding action
Added a jig handle (rockler, about $10 bucks) for better control
added an adjustable UHMW piece with two bolts that slips onto the fence above the runners to prevent tipping forward and only allow forward/backward movement
added a larger phenolic face plate to provide a bigger area to clamp to and more rigidity. It can be removed for smaller work.
So, after a bit of a delay getting all the stock ready to go, I finally put my new and improved right angle jig to use. I must admit I was quite nervous as the two side panels were 48" long, and the 36" top is a beautiful piece of birdseye maple. Funny enough, it worked! And it worked surprisingly well at that. The sliding action was smooth and precise, and the pieces were quite stable and machined well. The two end pieces were done together, and when clamped upright with a backing board produced a wide enough surface that was very stable.
The thing to watch is the fence itself will flex if you aren't careful. It's aluminum and lacks the rigidity and precision I'd like to have. The wider the piece, the more it can act as a lever and flex the fence if you aren't careful to advance it evenly and smoothly. That said, if everything is set up properly I can attest to the fact that you can dovetail a 48" high board with precision.
One thing I didn't take into account was the height of the backing board. As you can see from the pictures, unless you use a 12" high backing board, the height of the larger phenolic plate is largely wasted. I think I may buy some cheap flat pine and make a couple of 24" high by 12" wide boards specifically for backing large case work. I'll just cross cut the dovetailed end off after each use, so that should give me 12 to 15 or so cuts. I do think the plate provided more stability and a more rigid clamping surface even with the smaller backing board.
FWIW, I also needed to make a sliding dovetail for the bottom shelf, and tried a couple of different approaches to make the male ends. I ended up using two rockler right angle plastic clamp guides to stabilize a 36" shelf that I dovetailed the ends on. After extensive testing on scraps, I got it to the precise width and a tight but smooth fit. Boy did that work well, and I'll be using that joint more in the future. Being able to tune the fence .001" at a time really made the fit precise, and no issues with the glue altering the fit. I'd read a few horror stories, including one by David Charlesworth, so I was prepared for the worst. A couple of taps with a deadblow hammer at the end was all it took to assemble perfectly.
Pics attached. Again, it may not be anyone's first choice, but it worked out well enough that I wouldn't hesitate to do it again in the future.
Cheers!
Just to be clear: given the choice, I can't say I'd recommend the Incra as your preferred tool to make dovetailed casework. And although I think there is an Akida jig (and definitely an LN dovetail saw) in my future, the Incra is what I had to work with right now. Necessity is certainly the mother of invention, and it worked well enough that I though I'd share the relatively minor design changes I made to make it work for me. There are also a couple of other threads that touch on routing large upright pieces on an Incra (and the desire to see such a thing) so pics are attached!
The biggest issue was the right angle jig. I found the design to be subpar, and with an idea or two from some creative australians over at woodworkforums, I made a few improvements:
Replaced the plywood runners with longer UHMW ones. They provide more stability and greatly improve the sliding action
Added a jig handle (rockler, about $10 bucks) for better control
added an adjustable UHMW piece with two bolts that slips onto the fence above the runners to prevent tipping forward and only allow forward/backward movement
added a larger phenolic face plate to provide a bigger area to clamp to and more rigidity. It can be removed for smaller work.
So, after a bit of a delay getting all the stock ready to go, I finally put my new and improved right angle jig to use. I must admit I was quite nervous as the two side panels were 48" long, and the 36" top is a beautiful piece of birdseye maple. Funny enough, it worked! And it worked surprisingly well at that. The sliding action was smooth and precise, and the pieces were quite stable and machined well. The two end pieces were done together, and when clamped upright with a backing board produced a wide enough surface that was very stable.
The thing to watch is the fence itself will flex if you aren't careful. It's aluminum and lacks the rigidity and precision I'd like to have. The wider the piece, the more it can act as a lever and flex the fence if you aren't careful to advance it evenly and smoothly. That said, if everything is set up properly I can attest to the fact that you can dovetail a 48" high board with precision.
One thing I didn't take into account was the height of the backing board. As you can see from the pictures, unless you use a 12" high backing board, the height of the larger phenolic plate is largely wasted. I think I may buy some cheap flat pine and make a couple of 24" high by 12" wide boards specifically for backing large case work. I'll just cross cut the dovetailed end off after each use, so that should give me 12 to 15 or so cuts. I do think the plate provided more stability and a more rigid clamping surface even with the smaller backing board.
FWIW, I also needed to make a sliding dovetail for the bottom shelf, and tried a couple of different approaches to make the male ends. I ended up using two rockler right angle plastic clamp guides to stabilize a 36" shelf that I dovetailed the ends on. After extensive testing on scraps, I got it to the precise width and a tight but smooth fit. Boy did that work well, and I'll be using that joint more in the future. Being able to tune the fence .001" at a time really made the fit precise, and no issues with the glue altering the fit. I'd read a few horror stories, including one by David Charlesworth, so I was prepared for the worst. A couple of taps with a deadblow hammer at the end was all it took to assemble perfectly.
Pics attached. Again, it may not be anyone's first choice, but it worked out well enough that I wouldn't hesitate to do it again in the future.
Cheers!