- Home Improvement
How to use a Router
Using a router
There are two main rules to remember when using a router. The first is that the machine has a low torque (turning power) so if you attempt to give it too much work load, for example by trying to make it cut too deeply, then it will stall.
The bits cut their way through wood only by rotating at very high speed, and if the machine is slowed down by being asked to remove too much material at a time, the bit will tend to burn the wood, and quickly become blunt. When making deep cuts, take two, three, or even more, 'bites' at the cut, gradually increasing the depth with each pass.
Most manufacturers give in their instructions the maximum depth they expect their routers to cope with in a single pass. This depends not only on the router but also on the width of the cut and the hardness of the material with which you are working. (It also depends on the cautiousness of the manufacturer, so it is not wise to use the manufacturer's figures as a guide to how 'good' their router is.)
By far the best guide to how much material can be removed in one pass is your own experience. Start by removing no more than 3mm (with cutters over 12mm diameter) or 5mm (with smaller cutters), and increase the cutting depth as you gain confidence and knowledge. If you hear the whine of the motor drop in tone, its speed is dropping and you are overloading the tool; stop at once, and reduce the depth of the cut.
The second rule of routing is always to move the tool against the direction of rotation of the cutters; this forces the cutter into the edge of the wood (or the whole tool against a guide, if you are working away from the edge of the material). If you were to push the router in the opposite direction, you would find it virtually uncontrollable.
With some experience, it becomes second nature to move a router in the right direction; but until that happens, find some easy way of remembering how to move the tool. One method is to consider the side of the wood you are working on as part of a large circle, and to move the router anti-clockwise (viewed from above) around the circle. This applies if you are cutting on the outside of the wood, as you generally will be. However, if you are making a pocket or hole in the middle of a piece of wood, you must move the tool clockwise round the circumference of this hole.
Having selected your desired router cutter, fit it into the collet on the router's drive shaft. This is normally done using a small open-ended spanner (often supplied with the router i to tighten the collet around the shank, but follow the manufacturer's specific instructions on how to fit and change cutters: if you do not do this job properly, you may damage either the cutter or the collet.
Next, set the depth of cut. There are various methods of doing this depending partly on the type of router you have. With a simple, non-plunger router, the easiest method is simply to alter the depth adjustment (the method of doing this varies from router to router) until the cutter protrudes through the baseplate by the amount you want-check this roughly by eye, or by measuring with a rule.
Some routers have a calibrated guide on the depth adjustment. There is no zero on the guide because this will vary depending on the cutter fitted. But you can establish the zero point for any particular cutter by placing the router on a flat workbench and carefully altering the depth setting until the bottom of the cutter is just touching the bench.
These methods are fine for rough setting but for best accuracy the usual rule applies: make a trial cut on a piece of scrap timber before trying the real thing. If you have to make several cuts to exactly the same depth, the best plan is to do the initial passes first on all the pieces involved, then set the depth accurately and make all the final passes. This can save a lot of fiddly depth resetting.
Sometimes, though, you have to change settings in the middle of a run and in this case it might be worth making a gauge piece. This is a piece of wood planed to the exact depth that the cutter protrudes. To reset the previous depth accurately you simply put the gauge on the bench, rest the baseplate on the gauge so that the cutter is clear of it, and then alter the depth adjustment until the cutter is resting on the bench surface. You can also use this method when you want to rout out, say, hinge housings; using the hinge as a depth gauge, the router will be set to take out exactly the right depth of material.
Depth adjustment on a plunging router is a little different. The usual technique is to stand the baseplate on the workbench then plunge the router down carefully until the cutter is resting on the worksurface: the router can then be locked in place. The depth of cut is usually altered by means of a threaded rod-the distance below the bottom of the rod and the stop on the baseplate gives the depth of cut. Again, there are calibrated guides to help set depths; and again for greatest accuracy, it is sensible to make a trial cut first.
One advantage of a plunging router is that it is not necessary to set the depth of cut for intermediate passes- you just avoid plunging down the router to its fullest extent. A depth gauge can easily be used with plunging routers. Put the gauge on top of the depth stop, and screw the threaded rod down on to it: remove the gauge and the depth is accurately set.
Routing on or near an edge
Using a router to put a decorative edge along the length of a piece of timber, or a slot in the face of the timber near the edge, is probably the most frequent operation. The easiest method of controlling and guiding the router is to fit it with a side fence or edge guard. This presses against the edge of the timber and, as long as you move the router in the right direction, helps to hold the cutter against the wood, so that the position of the cutter relative to the edge of the timber can be varied. Since both the depth and position of the cutter can be varied, various sizes of molded edge can be produced using just one cutter-and depending on the cutter different shapes may be possible too.
It will take some time to get used to the pull' of the router, and to gauge how fast to work. It is best to start the cut at the end of the timber, and make a steady pass at your chosen depth and guide setting right through to the other end. Do not move the router too slowly otherwise the wood will singe and the cutter will become blunt: on the other hand do not force the pace or you will overload the tool, with much the same results.
When cutting along narrow edges, the baseplate of the router is not very well supported. If you find this makes it difficult to hold the router upright, clamp packing battens to either side of the workpiece to provide a broader support.
Another method of routing along the edge of a piece of wood is to use a pilot bit- a cutter with a guide pin mounted on the bottom of the shank. The guide pin holds the cutter against the timber, and so a fence is not required. By altering the depth of cut, some differences in shape can be produced from the same cutter; but without the fence, you cannot adjust the distance into the edge of the timber to which the cutter can be set.
Routing away from the edge
Routers are particularly useful tools for making slots (housings) in the middle of panels of wood and they can be used just as effectively across the grain as with it. Unless the housing is very near the edge of the wood, you cannot use an edge guide. Instead, the technique is to clamp a batten to the workpiece, and guide the edge of the router's baseplate against this. But take great care in setting the position of the batten to get the cut accurate as there is no adjustment on the router itself to help you.
Stopped housings-those that do not go from edge to edge of the workpiece-are easy to make with a plunge router. Position the router above the start point. plunge down and start routing. However. the technique is a little more tricky with non-plunge routers. One method involves tilting the router from a horizontal through to the vertical position using the edge of the baseplate as a pilot, in much the same way as a plunge is started with a jig saw.
To cut a housing wider than that of the router bit, you can move the bottom guide and repeat the routing process. But to cut very much wider housings would be a little tedious, since you would be continually resetting one guide or another: with a bit of practice, you should find that you can do most of the work freehand, relying on a batten guide only for the final pass when cutting the edges of the housings accurately to width.
Slots or holes are cut in much the same way as housings except, of course, that for large holes you do not need to bother removing the middle of the timber: this will drop out when you complete the circumference. Remember, too. that for internal holes like this you must move the router in a clockwise rather than an anti-clockwise direction.
Routing in circles
With most routers, the edge guide can be adapted to form a trammel bar an adjustable guide which allows the router to move in a perfect circle. This facility can be used for cutting out holes, or forming round plates of wood. And although you could often use a jig saw instead, a router can put a decorative edge on the work at the same time. Decorative paneling is another case where the work can look more attractive if you cut straight, circular or part-circular moldings into it.
One use for a router is to form complicated designs and cut-outs. If you are unsure of your ability to cut the design accurately (perhaps on an expensive piece of hardwood), or if you want to repeat the design several times, the answer is to make a template first. This is a copy of the work you want to do, formed as a series of cut-outs in a piece of firm timber-say, good-quality plywood about 8mm thick. You can of course use the router to form the template: if you make a mistake you may not need to throw the whole piece away and in any case you will not have damaged anything irreplaceable.
In use, the template should be placed over the workpiece and a special template guide fixed to the router base, with an appropriate cutter mounted through it and fixed to the collet in the normal way. Move the router so that the guide bears against the sides of the cut-outs in the template, enabling the cutter to follow shape and make an accurate copy on the workpiece.
The one thing to watch out for when using templates is that the diameter of the cutter is normally different from the diameter of the guide, meaning that the size of the cut in the workpiece will differ from that in the template. Allow for this before you start making your template: select which cutter and guide you will be using, and follow the manufacturer's instructions on how much larger or smaller the template cut-out therefore has to be.