Wednesday 11 July 2018
This is probably the simplest and quickest router jig you will ever make, but it is a certainly very effective way of making your own dowels. You won't need much in the way of materials to make it, though the router does have to be mounted under a proper table. Otherwise all you need is a thin strip of strong timber the length of the router table and a short block for the guide section, (pic 2). The two pieces are held together with bolts and wing nuts only because I anticipate developing it into a modular system with different guide blocks for different sized dowels. For a one-off jig the two pieces could be glued and screwed together.
The block requires two accurately drilled holes if it is to guide the timber properly. One hole has to be the exact diameter of the finished dowel, this is the outfeed hole. The other infeed hole has to have a diameter equal to the diagonal length of the end cross section of the initial timber. Don't worry about having the exact size; just vary the initial square section to suit the bit diameters you have provided they are not too far out.
The important thing is that these two holes are concentric and they meet in the middle of the block. Use a drill press, drilling the larger diameter first and then following on with the smaller one, (pic 3). Sawtooth or forstner bits will leave a clean and accurate hole, (pic 4), this being the only critical part of the jig. If they are out of line the dowel will not feed through properly.
Next drill a hole through the face of the block of a diameter to match that of the cutter you are going to use to form the dowel, (pic 5). I just used a 12mm straight bit, which left a reasonable finish but I wonder if a core box cutter with its rounded end would be more gentle.
Now bolt this block to the middle of the support strip, having first drilled a central opening to allow some leeway when you are setting it up on the table, (pic 6).
As the cutter settings are critical it is also essential to have a fine height adjuster on the router so you can make tiny adjustments if necessary. Fix the router under the table and set the cutter so that it protrudes through far enough for you to locate the block over it. Fix the support strip in this position by clamping it to the table at either end, (pic 7). Wind the cutter up until the tip just lines up with the diameter of the outfeed hole, (pic 8).
With the router running, now feed the square section into the infeed hole and rotate it against the cutter to start forming the dowel, (pic 9). The initial results were rather disappointing and although the dowel was formed the finish was poor and uneven, (pic 10).
This was improved a lot when I waxed the inside of the outfeed hole to make the emerging dowel slide more freely as it also allowed me to drop the cutter fractionally and make the fit correspondingly tighter,
(pic 11). I also realised that the square section was also slightly undersize and was rattling about slightly in the infeed hole (pic 12). There is no correction for this, just re-machine the blanks a bit bigger. However, although these modifications helped a lot the finish was still not as good as I needed and a rethink was necessary. By chance I came across an illustration in an old magazine showing a bar fed lathe where the material was rotated as it was fed in to a revolving cutter. This set me thinking about rotating the dowel material, the obvious method being via an electric drill. I screwed a large screw into one end of the blank, cut the head off to form a gripping spigot, (pic 13). This is then held in the drill set to rotate at about 500 rpm and the spinning blank is fed in as before, (pic 14). Now the results are totally different and a smooth, even dowel forms very rapidly, (pic 15). In fact the combined rotation of the cutter and he blank actually pulls the material through the jig and a whole length is formed in seconds, (pic 16). You have to actually hold it back or the cutter will jam.
I had great fun knocking off dowels in a range of different timbers, (pic 17), experimenting with both the speed and the direction of rotation. Putting the drill in reverse eliminated the pulling action and resulted in an even better finish, but the danger is that the gripping screw undoes, so a different holding device is probably needed for the final version. Spinning the drill faster seemed to make very little difference once you get above about 500 rpm, which is good as if you go any faster it becomes difficult to control.
You can modify the set up to form a tenon on the end of the dowel by feeding the dowel back into the same jig but now with the cutter raised up. To form an even shoulder make an adjustable stop with the grain running lengthwise, (pic 18). With this in place feed the dowel back into the outfeed hole and adjust the cutter up to cut the required tenon diameter, (pic 19). You only need to hand feed this bit rather than use the drill, but spin it several times with the stop up hard against the side of the jig to make sure the tenon shoulder is perfect, (pic 20).
To round over the end of the dowel you just use an ovolo cutter to form the necessary shape. The guide block for this is similar to the first one but it clamps directly to the router fence, as there is not enough reach on the cutter to go through the support strip as well, (pic 21). There are just two holes in this one. The side one is the same diameter as the dowel again while the one on the face is any size that is big enough to enclose the ovolo cutter, (pic 22).
For extra support for this job I also used the first jig clamped to the table as a stabilising block and it allows you to use the adjustable stop to control the cut as well, (pic 23). A few quick rotations produces the perfectly shaped end, (pic 24). It actually takes longer to set up the stop than it does to do the job.
It may all seem a bit long-winded but once the jigs have been made there is no limit to the type and size of dowelling that can be produced, and you don't need a lathe!