Cutting a circle of wood by hand is often tricky, although the tests I have done so far with this jigsaw table have been quite satisfactory. Anyway, the best option is to make a circle jig to cut the circles in wood. A woodworking jig such as this simple one that I make in this blog post.
So, let’s see how to make a circle cutting jig and how to use the jig to cut circles out of wood on the jigsaw table.
Para hacer esta sencilla guía de carpintería voy a aprovechar el carro para cortes a inglete que había fabricado (y que es igual a la base del carro de escuadrar madera que también había hecho), y que como algunos ya sabéis no me dio el resultado esperado. No es más que un trozo de chapa de marquetería, con un par de listones debajo que encajan en los laterales de la mesa de la sierra caladora, y que desliza enfrentándose a la hoja de corte.
To cut the circles I will need some space on the right side, so as the plywood base of this sled is too small I will screw to it a piece of a pine board I had in the workshop.
I screwed it flush to the back edge of the thin plywood base, and offset as far as I can to the right, but so that if necessary I can still clamp it with a clamp on the left.
Now I take the sled to the jigsaw table again, and turn it on to cut a slot in the wood. Whenever I use this circle jig the jigsaw blade will fit into this slot.
And the radius of the circle to be cut will be perpendicular to this slot. Then, I draw a couple of lines perpendicular to the slot.
And on these perpendicular lines I will mark the radii that I consider necessary. As I said, I mark the radii on these lines. On one line I mark even numbers (even centimeters) and on another line I want to mark odd numbers (odd centimeters).
And with a fine drill bit I drill pilot holes at all marks. I drilled them by hand, but it is more accurate to drill with a drill press or with the help of a drill stand. And if at some point I need to make a circle whose radius does not coincide with any of the marks I made, I just have to draw another perpendicular line to the slot, mark the necessary radius and drill the corresponding pilot hole.
As a pivot pin I can use a nail, but I think that a nail would deform the circle jig holes and they would loosen if I cut too many wood circles. That’s why I prefer to use a screw, but I had to file off half of the thread.
This way I can screw it into the corresponding hole and it will stay firm as many times as I need to use it.
Now the trick to use this jig for cutting circles is to put the jig on the jigsaw table in a way that the line where the radius I am going to cut is, and which is perfectly perpendicular to the slot, is right on the teeth of the jigsaw blade. When the circle cutting jig is in position, I have to put a clamp behind it to act as a stop. This way I know that when I go to cut the circle, the jig will go to its correct position marked by the stop.
To cut the circle I want, I cut a square of wood slightly larger than the circle I want, and I drill a guide hole in the center.
And now I fit that hole in the screw that will be the pivot point, and that I already screwed in the position corresponding to the radius of the circle I want to cut. I have to make sure that the surface of the wood is perfectly flat on the surface of the circle jig, and I have to be careful in case that the tip of the pivot screw protrudes from the top, lest I get it in my hand when I press on the wood.
And now I can start cutting the wood circle. I turn on the jigsaw, put the circle cutting jig on the jigsaw table and begin to cut the wood straight, not allowing the workpiece to rotate. This way I will cut straight until the circle jig runs into the clamp that I put as a stop.
And now holding the circle jig against the stop I start turning the wood, the workpiece, as I cut the circle. I have to cut little by little, but it is easy and I just have to be careful at the end of the cut, lest the saw gets into the inside of the wooden circle and spoil it.
Es mejor dejar que llegue al final con suavidad y no intentar retroceder y avanzar para mejorar el final del corte. Es preferible sacar el círculo y lijar con la lijadora de disco la pequeña imperfección que nos puede quedar.
