Router Guide Pt 2
Tuesday 14 October 2008
Andrew Lawton looks at basic techniques using straight fluted cutters
To fit a cutter, first ensure that the machine is switched off and unplugged. Lock the motor spindle by depressing the locking button and slacken off the collet nut if necessary and insert the shank of the cutter at least three quarters of its length: ensure that there is a gap of at least 4mm (5/32in) between the face of the collet and the webbed flange where the shank meets the business end of the cutter. Then tighten the collet, always using the spanner supplied with that particular machine, until firm resistance is felt.
The manuals always state rather vaguely : 'do not overtighten'. Excessive force can damage both the collet and the cutter shank and should therefore be avoided. Most if not all modern routers are cleverly designed so that if a cutter should happen to work loose, the collet nut prevents it from flying out of the machine completely, although the workpiece itself would probably be damaged by the slipping of the cutter.
This safety device can be felt when slackening off the nut to change the cutter: the nut reaches a point where it suddenly becomes stiff again, then with a further turn of the spanner, fully slackens off.
Set the depth of the intended cut in the following way: with the machine still switched off, rest the machine on the workpiece and depress the spring loaded columns with the handles until the cutter just touches the timber. Secure the columns in this position by turning the locking one of the two grip handles clockwise. Again, this shouldn't be done too viciously, just enough to set the columns in the desired position: too much pressure may result in the lockable column becoming distorted and no longer able to plunge up and down perfectly freely.
Adjust the depth bar to the desired position: the distance between the end of the bar and the screw at the top of any of the three rotary turret stops will determine the depth of cut. The purpose of the rotary turret stops is to allow three different depths to be set up, since it is important not to try and remove too much stock with any one pass.
Groovy applicationsGrooves have countless applications: for example, fitting back panels in carcasses. Mark the position of the groove from the edge of the board, preferably with a gauge, then set the fence to this. All routers come with an adjustable fence as standard and many, such as the Trend T5, have a fine adjustment feature which is most useful for accurate setting.
Set the desired depth of cut as previously described. Ensure that the workpiece is firmly secured to the bench to prevent it from tipping over the edge of the bench with downward pressure, or skidding along it. In which direction is the router fed to produce the cut? With a few exceptions which we will look at later, the rule is always to feed the router in the opposite direction to the rotation of the cutter. In other words, with the router mounted above the workpiece as in all hand-held operations, the cutter spins clockwise, therefore the router is fed anticlockwise - see fig 1.
Plug in the router, then rest it on the workpiece with the cutter fully retracted, switch on the motor, ensuring that the RPM doesn't exceed that stated for the cutter (unlikely with a straight cutter), depress the columns until the depth stop touches the turret, lock the guide knob and feed the router along the workpiece, from left to right, not so quickly that the motor labours, nor slowly enough to cause the cutter to heat up and possibly scorch the timber.
At the end of the stroke, slacken the grip knob, allow the columns to spring back up and switch off. The most difficult part is the start and finish, where the baseplate of the router has to be carefully balanced on the workpiece; this is similar to planing a piece of timber by hand. One way of making this easier is to position run-off boards of the same thickness at each end.
In many cases, such as frame and panelled doors, if long enough 'horns' are provided, there is enough of the workpiece projecting at each end to give enough support to the baseplate. Once mastered, cutting grooves with the router will be far quicker and more accurate than other methods.
Housing newsHousings are a second major constructional area where routers win hands down and differ from grooves by running across the grain rather than along it. When routing across the grain in solid timber, two points are worth mentioning. First, the housing should be marked out with a pair of parallel knife lines, not just to provide an accurate reference to work to, but the act of cutting through the uppermost fibres of the wood will minimise spelching and give a cleaner cut. Second, when a housing is cut across the full width of the workpiece, or all four edges routed in any way, the right sequence should be observed - see fig 2. This will prevent breakout at the corners.
If a housing is near the end of the workpiece, the fence can be used in the same way as in machining a groove. If, as is often the case, a housing is positioned midway along a cabinet side, for example, the standard fence bars will be too short to reach. Longer bars can be used but they tend to be unwieldy; a much better solution is to make a guide such as the one in the photograph. With a stock of carefully planed hardwood and 'blade' of MDF, such a device can easily be made in a variety of sizes to suit different jobs.
The blade must be perfectly straight and at 90 degrees to the stock. If the blade is sealed and waxed, friction and wear will be reduced. In use, the guide is carefully positioned and clamped to the workpiece.
An alternative to making a guide is to buy a device such as the Trend Clamp Guide, available in three lengths up to 1,270mm (50in). With a flick of the locking lever, the guide was moved progressively along the piece of timber being machined, with a fair amount of time saved compared with repeatedly having to slacken and tighten a G-cramp on our shop-made equivalent.
It is useful to have both the commercially and shop-made versions depending on the nature of a particular job.
For instance, I recently had to rout out a recess and found a Trend guide ideal. There are two versions: the basic clamp guide and the Pro Track. The basic version does have some slack in it, which renders it unsuitable, in my opinion, for the degree of accuracy required for fine furniture making.
The Pro Track version models use a grub screw to eliminate any. They are more expensive, but worth the extra cost in the interests of accurate work.
Rebating know-howThe third basic application of the router is for rebating. By definition, rebates are along either the edge or end of a board so they can be cut using the standard fence. Any size straight cutter may be used, though a 6mm or 9mm is suitable for most applications.
Rebating does however, present a potential pitfall in that certain timbers with long stringy fibres, such as ash, have a tendency to tear out, leaving an unsightly ragged edge when we follow the rule about routing in an anticlockwise direction.
To avoid this, mark out the limits of the rebate with a marking gauge. Then, for the first cut set the fence quite fine and draw the router backwards or clockwise as it were. This technique, known as 'backfeeding', can feel a little awkward at first, but has other applications as we will see in the next instalment, so it is worth mastering.