General Care and Safety

Always take extreme caution when removing the protective wax from a new cutter. Do not pull it off, as the sharp cutting edges could cause injury. Carefully slit the wax with a sharp knife along the internal angle of the flute and prise the coating away. Before using a new cutter, wipe off any protective oil to prevent it transferring and marking the surface of the work.

Never pull the cutter from the router by the cutting edges without protecting your hands. If your fingers slide along the cutting edges, you will find out just how sharp they are, then you'll delay progress whilst you receive first aid - and you could also bloodstain your wood!

Design

Whatever the size of the router bit shank, it is held into the tool with a collet assembly. This is simply a device which relies on tightening a nut against a taper to grip the cutter shank equally around its circumference. The router shaft (or arbor) is hollowed and threaded at the "business" end. The collet fits into this hollow, acting against an internal flange, or taper, once the nut is tightened. Some routers require that the arbor is held by a spanner whilst the nut is tightened:

Old-style shaft

Two spanners required

Others have a press-button spindle lock fitted, which holds the arbor, thus requiring only one spanner to be used:

Modern Spindle-lock

One spanner required

Older-style collets had a separate steel ring inserted in the collet nut. More advanced collet assemblies have a ring machined within the nut that engages the collet, automatically releasing it from the end of the spindle as the nut is undone. These are typically made of high quality, polished tempered steel and have multiple slits, ensuring both security and concentricity for the cutter. They also feature slits starting from alternate edges of the collet to provide even pressure over the full surface area of the cutter shank.
Old-style Collet	Side View Drawing	Double-lock Collet

A double-lock system is incorporated by some manufacturers. When the nut is undone, it will first loosen and then appear to re-tighten, requiring loosening a second time. This design prevents the cutter shank being released if the collet nut accidentally loosens while the router is running. The latest design collet systems have their collet and collet nut factory assembled and should not be separated.

Collet Safety

Always insert as much of the shank as possible into the collet and at least three quarters of the shank length as a minimum, to decrease the chances of deflection of cutter when under load. This in turn will prevent damage to the collet, reduce wear and stress on the router bearings and avoid the possibility of shank damage. However, don't allow the end of the cutter to be in contact with the internal end of the armature recess. Always maintain a gap (see diagram) of 1/16" (1.5mm). This will prevent the possibility of any "hammer action" being induced which could cause the cutter to creep out of the collet (the collet nut is represented by a rectangle, for clarity).

Never clamp a short portion of the shank in the collet to gain extra length!

Never use collet reducers (shown in blue here) as a means of extending the length of the shank!

Always ensure that you have a minimum gap of 5/32" (4mm) between the collet and the cutter (shown here in red).

Cleanliness Pays

Make sure that the collet is kept perfectly clean and corrosion-free. Resin can work its way up the slits of the collet and build up around the cutter shank and the inside collet faces. Resin build-up may cause uneven contact between the internal collet face and cutter shank. This could create a resonance, causing the shank to slip and leading to collet burn, deposits being evident on the shank as brown marks. Resin build-up can be removed by using an appropriate solvent and a fine wire brush.

Surface corrosion can also occur on the inside face of the collet, which will restrict insertion and removal of the cutter. It can also cause scoring of the mating faces and could significantly damage the collet - sometimes beyond repair.

Dust, corrosion or dirt will decrease the ability of the collet to grip or release the cutter shank. Other problems include the shank slipping, bit or collet seizing, or excess vibration leading to shank bending or breakage. A fine wire brush will remove such deposits, but don't use glass-paper as this will leave scratches, which could cause further problems.

If either the collet or its nut are faulty, it is best to change both as soon as possible. Don't use cutters with damaged shanks, as this will lead to trouble. To prevent cross-threading and damage to the threads of the collet nut, the inside of the nut should be kept clean and free of burrs. If in doubt, replace the nut at the same time as the collet.

Keep both the inside and outside tapered surfaces of the collet clean and free from dust, resin and dirt. This also applies to the inside taper of the arbor and the threads of the nut and arbor. Remove any deposits with a wire brush and regularly protect the surfaces with light oil or anti-corrosion spray.

Keep It Cool

A problem can arise from metal fatigue in the collet, due to heat being transferred from the cutter, as repeated heating and cooling cycles may alter the original steel tempering. Sprung steel requires a degree of inherent elasticity in order to properly grip the cutter shank. This is reduced over time and increased tightening of the collet is then needed. This will eventually distort the collet, preventing it from exerting an even grip. Therefore, collets that need excessive tightening should be swiftly replaced.

Bad Vibrations

If vibration is noticeable when you are routing, switch off at once and investigate. First, check that the cutter shank is not bent, that the cutter is not damaged or blunt and that the cutting edges are not chipped. Vibration can result from a worn collet, which is holding the cutter out of line to the arbor axis. This may be due to a condition called "bell-mouthing" within the collet. Collet marks on the shank will show that the collet is worn and this can be checked by inserting a long cutter and tightening the nut. Apply sideways pressure on the end of the cutter and if there is any sign of movement, the collet must be replaced.

Replace the collet and the nut at the same time. If there is no apparent wear in the collet or nut, the problem may be wear on the arbor, or within the router's main bearings, both major service tasks.

Finished For The Day?

Always remove the cutter from the router after use. This will avoid continual pressure being applied to the collet and the cutter shank, which could, in time, cause a permanent distortion. After cleaning, lightly oil the collet before storing, particularly in humid conditions, to avoid corrosion or surface pitting.

Correct Feeding Essential

The feed direction is the direction in which the cutter is fed into the material or, in the case of table mounted or fixed routers, the material into the cutter.

Following the correct feed direction will ensure safer and easier working, and allow the cutter to cut efficiently. The correct feed direction is always against the rotation of the cutter. This can be ascertained by looking at the cutter itself. Routers rotate in a clockwise direction (when looking down from above the machine) and this determines the direction in which the cutter rotates and - subsequently - the feed direction.

If the feed direction is incorrect, the forces involved in cutting will cause the cutter to try to drag the router along the workpiece. This situation can swiftly become unstable and dangerous, particularly if it takes the operator by surprise.

When routing inverted in a table, the feed direction is right to left. If the material is inadvertently fed in the wrong direction, it could be ripped away from the operator and - in the worst case - drag the operator's hand into the cutter. Whilst it is possible to take a very light "cleaning" pass in the "wrong" direction (known as "climb cutting"), this is an operation that should only be attempted when the operator is fully conversant and totally confident in handling and controlling their machine.

It is a good practice to mark the direction of feed (right to left) on the worktable fence when using your router inverted in a table. With portable routers, the rotational direction of the cutter is often marked on the machine, although with experience this will become second nature.

Speed Is Important

Many modern routers have variable speed, set with a thumb-wheel or slider. Some have a recommended speed chart attached to the router body, like this one which relates to the markings "A" to "F" on the speed thumb-wheel and speeds of between 10,000 and 23,000 rpm. Routers with a single speed will rarely be able to use large cutters, as they will exceed the RPM recommended by the cutter manufacturer. Separate variable speed controllers are available for connecting between the router and the power source. However, these are unlikely to offer full wave rectification or speed compensation and do not maintain the available power evenly throughout the speed range. Inferior types of speed controller can also affect the smooth running of a router, particularly at lower speeds.

To minimise wear on the router motor bearings, to prevent cutter damage and to improve the finish of the cut face, it is important to maintain a constant feed speed. Variations in the type of material, type and condition of the cutter and the available router power will all have an effect on feed speed. It is for the woodworker to judge, by the sound of the router motor, whether the motor is labouring. In time, you will acquire a feel for the router and a feed speed relative to the work in hand will come naturally. You will find that a narrow cutter can be used at a higher speed than a wider one, although very narrow cutters will need a slower feed speed and smaller depth of cut to prevent breakage.

Feed speed will also be affected by the type and density of the wood, the grain direction and any variation in the texture of the material along the cutting line.

Beware of hard knots as these can damage the cutting edges or even chip or fracture the TCT tips. Also avoid 'dead' or loose knots, as they can be ejected and cause injury, as well as causing tip fracture.

If the cutter is inclined to burn the material, it is a sign that the cutter is blunt, or that it is being fed along the cut too slowly.

Working With Templates

Templates are very useful for the production of identical parts all at one time, or the exact replication of a part at any later date. They can be used in a couple of different ways, either with a bit that is equipped with a guide bearing, or by using a guide bush in the router base.

If the bearing-guided cutter is to be used, the template must be made to the exact size of the finished article. Whether the bit has the follow bearing at the bottom (as in "A") or the top of the cutter (as in "B")  - some specialist cutters have both - dictates how the template is used with the stock material.

When using a bit with a bottom-mounted guide bearing, the template must be BELOW the stock to be routed. The bit depth is adjusted to ensure that the bearing will contact the template, then engaged with a sideways motion. Once the bearing is in contact with the template, it will follow the template shape, removing excess stock until the shape matches that of the template. To save stress on the cutter, first remove as much excess material as possible from the stock (jigsaw, bandsaw, etc.), then there will be less material for the router bit to deal with.

When using a bit with a top-mounted guide bearing, the template must be ABOVE the stock to be routed. The bit is adjusted to again ensure that the bearing will contact the template, then engaged with a sideways motion. Once the bearing is in contact with the template, it will also follow the template shape and remove excess stock until it matches the shape of the template. As before, first remove as much excess material as possible from the stock.

Working With Guide Bushes

	Using a guide bush in the router base is another common way of following a template, with two major differences. The first is that there is no need to use a bearing-guided cutter - a straight cutter is suitable for the task.
Secondly, the size of the template will differ from the intended finished article. With internal templates, such as a circle-cutting design where the guide bush follows an internal edge, the actual template will need a hole larger than the finished dimensions by the distance between the outer surface of the guide bush collar and the cutting edge of the bit (the collar-to-bit offset), as shown here.
	Therefore, when cutting a template for hinge fitting, because you are cutting the mortice using internal edges, the template has to be larger than the hinge by the collar-to-bit offset.
For external templates, where the guide bush collar follows an external edge, for example, when making a curved shape, the template will need to be smaller than the finished dimension by the collar-to-bit offset.

When a router follows a template, it will reproduce everything it follows, including lumps, dips and roughness. So one thing is clear - the more time you spend in getting the template edge absolutely smooth and free of imperfections, the better the finished result will be. My preference for templates is MDF, because I find it easier to get a smoothly-sanded finish on the edges than I do with plywood.

The router is a very versatile tool and one that is very satisfying to handle skillfully. As with any other skill or technique, practice is the main ingredient to success.

Above all, please BE SAFE!

Safety "A to Z"