sliding on the rods
Some time ago I commented that I was going to experiment with sliding my router across the rods. I did some preliminary experiments a while ago but I got into it in greater detail today. Here's the results:
The objective was to cut lap joints quickly and accurately. Well, accurately -- not bad but quickly -- no way.
First, my setup:
1. my shop runs on 2' x 4' modules that are on casters and locks. Some tops are fixed and others slide off for access to "bins" underneath.
2. some of the tops are MDF that are fixed into place and others are plywood of various types and these are usually removable.
3. the module that I used to setup the experiment uses plywood for the top and the top is removable. This is important, later.
4. I'm building two rolling bases to raise the washer and dryer to a more convenient height. My wife says she wants them to be 6" higher.
5. I size four sticks to 1 1/4" x 2 1/4" x 31" long and four others to 1 1/4" x 2 1/4" x 33" long. That means that I need to cut two dados in each stick.
6. I took four of the sticks, located them on the table top and locked them (I thought) in place with a caul. Except the table top flexed and they were less solid than I expected. I ended up having to take a chunk of something large and heavy and use it to support the table top. That worked.
7. Next I assembled my short skis (18" rods) and laid it over the workpiece with the router "loaded." There wasn't enough room to slide the router across the workpieces. I tried a bit of a cut and it was obvious that this wasn't going to work. I took off the short rods and put on my long ones (30"?) Now I was loaded for bear!
8. Now, I'm not blind but details are a bit harder to see so I use a magnifying glass when I'm trying to work with close tolerances. Except, the magnifying glass was useless where it was and nowhere could I put it where it seemed useful.
9. Next the router was on the wrong side of the cut so I moved over to the other side of the table and tried that. It worked but it was rather uncomfortable trying to wrap my rather copious stomach around the sticks hanging off the back side of the table while I leaned forward attempting to see what's going on.
10. That wasn't the answer either. Also the clamps supporting the table top were in the way and I just couldn't wrap myself around an squeeze in to accomplish what I wanted to. I completed the cut but wasn't happy with the contortions.
11. I switched the skis over to the other side of the caul, pushed the supporting clamps out of the way and now things started to work.
12. I controlled the forward and backward of the cut with the skis and kept the cut straight with the rods. It worked a charm. You'll notice in one of the pictures I mark "the perfect cut." I mark where the cut should be with a striking knife. This cuts a deep groove in the fibres of the wood so when I use a saw or router, the cut remains clean. Holding one side of the skis and using it as a guide and sliding the router across the rods with the other hand is the way it's done. I watch the scarf coming up from the router cut into the knife cut and when there is no scarf, that is a perfect cut. You can see a bit of it in the picture. The others parts of the cut are only off by a few thousandths but they're not perfect.
All in all, the method is feasible. But my observations provide the following:
A: square your stock to the cauls. Then, use the caul as the equivalent to a fence so the skis are restricted by the cauls.
B: I thought that the router sliding across the rods was all the control that I needed. I found that I located the router with the skis but controlled the cut with the rods.
C: My original notes on skis found that control was absolute and control was to the thousandths of an inch. This is further borne out by the sliding of the router across the rods controlled by the skis.
D: Now, this works. The downside is the degree of assembly and the preciseness required in the setup. Somewhere I'm going to get a parallel ruler and see if that will help make setup feasible.
E: The third picture was the final working position that I tried. Notice how the caul is restricting the movement of the skis, like a fence. I also worked looking over the router as it cut. I controlled the start of the cut with the left ski, I pushed the router along the rods with my left hand, looking over the top of the router, and controlled the width of the cut with the right ski.
F: one more observation. When I pushed down on the router to set the depth of cut, the rods deflected. You'll notice in the second picture a small piece of plywood beside the ski. I used that as a "starter" to set the depth of cut. I would start the router, off the workpiece, set the depth with the block, then move the router into the workpiece.
Last edited by allthunbs; 04-05-2011 at 05:09 PM.