Routers

The basic router is extremely simple.

In general terms, it's a motor and several crucial controls. The motor can range up to about 3Vi horsepower and can turn anywhere from 10,000 rpm up to around 30,000. A rotary cutter is fitted into the collet on the lower end of the router motor. It is direct drive in the purest form. But just to complicate things a bit. a huge variety of cutters is available. (See the chapter "Bits.") Being the business end of the machine, the cutters largely determine what you can do with the router.

There are four main pans to a router the motor, the collet, the base, and the baseplate.

The motor is the type known as a universal motor, the same sort that's used in your other portable power tools. (Your table saw, jointer, and other stationary tools use a different kind of motor called an induction motor.) The power ratings of the motors used in routers range from Y4 horsepower up to about VA horsepower. The more power the motor has. the bigger the router is.

The collet is a simple but accurate chuck. Attached to the end of the motor armature, it holds the bit so the motor can make the bit spin. Designs vary, and some collets are intrinsically better than others. All collets, however, allow you to change bits.

The router base is what holds the motor, positioning it in relation to the work. It usually incorporates two handles so the operator can hold and control the machine. One of the most critical elements of the base is its depth-of-cut adjustment mechanism. There are two fundamental types of bases: the fixed base and the plunge base. The type of base your router has is pivotal to what your router does, how it handles, and what it costs.

The baseplate is a plastic sole on the bottom of the base. It serves as a bearing between the router and the work, enabling the router to slide smoothly across the work without marring it.

Let's take a closer look at each of these four parts.

THE MOTOR

Here's a curiosity. Mentally check over the power tools you have, and those you'd like to have. What is the measure of utility or capacity most commonly used with each tool? Does any, other than the router, depend upon its horsepower rating as the primary measure?

You talk of your table saw. circular saw, chop saw, or radial arm saw in terms of the blade diameter first. Drills? Chuck capacity for portables, measure from chuck to column for drill presses. Band saw? Depth of the throat. Planer or jointer? Length of the cutting knives. Sanders? Size of the sanding area or belt.

But with the router, it's the horsepower rating you mention first. You're going to find that's so throughout this book (I know that because we've already written most of it). There are some other measures that might be meaningful—collet capacity, range of motor travel, baseplate diameter (or length and width for a rectilinear one), weight. But the power raring conveys the size of the bits it will drive, and suggests a size and weight.

BRUSU BRUSU HOLDER

COMMUTATOR-END SM.L BE.A.RIU1J

KMOB,

COMMUTATOR-END SM.L BE.A.RIU1J

KMOB,

ROUTE*:

TUE.

INSIDE 3T0RV

ROUTE*:

TUE.

INSIDE 3T0RV

Bio Hrwerk Reaktor Selbstbau

ADJUSTMENT KNOB

THE. INSIDE STORY

ARMATURE. SHAFT

COMMUTATOR-END BALL BEARING

POWER CORO

BRUSH HOLOER

COMMUTATOR

ARMATURE

BRUSHES

PLUNGE CUIDE BAR V

PLUNG.E LOCK

L FIELD r;

TUREAOED

ADJUSTMENT

FAN-END BALL BEARINÇ

PLUNCE TUBE

COLLET1 AMO NUT

DEPTH-STOP TURRET

BASEPLATE

Power Ratings

What may be more important than the horsepower rating, however, is the amperage rating. The amperage rating of each tool is assigned by Underwriters Laboratories (UL). It is the maximum amount of current the tool can draw in continuous use without overheating and, eventually, burning out. (Overheating is defined as raising its temperature more than 60° Celsius above ambient temperature.)

Horsepower ratings, on the other hand, are assigned by the manufacturers themselves, based on tests they've conducted. The horsepower rating may reflect a marketing plan as much as it reflects the design engineer's intent for the tool.

The rating procedure usually begins with the motor mounted on a dynamometer, which applies artificial loads as the motor runs. Speed and torque data are recorded as the test ranges from a no-load state to the point at which the load simply stalls the motor. The data are charted as the horsepower curve, and that is generally reported in terms either of peak horsepower or of continuous horsepower. And, of course, there's a ccrtain amount of data massaging involved—rounding up to the nearest quarter horse, for example.

Peak horsepower is the absolute maximum horsepower generated.

General-purpose routers range in size and power from a small

1-horsepower model (left centcr) through 2-horsepower models to the 3-horsepower, 18-pound production behemoth (far left). Even plunge routers are available in a range of sizes: 1-horsepower (right center),

2-horsepower, and 3'/*-horsepower (far right).

very probably when the motor is drawing two to four times the UL's amperage rating and consequently starting to overheat, stink, and smoke. (According to one manufacturer's documentation of its test of its 15-amp router, the motor was pulling 54 amps at the moment it squeezed out its 3 horsepower. That's an in-aedible draw, and translates into a lot of heat.)

Continuous horsepower is what the motor can produce during continuous, safe operation, meaning hours of operation when drawing no more than the UL's rated amperage.

The industry convention is to report peak horsepower on a universal motor, the type that drives a router, and continuous horsepower on an induction motor, the type used in stationary power tools.The universal (brush-type) motor is used primarily for intermittent, variable-speed operation. The induction (brushless) motor is used primarily for long-term, fixed-speed operation. These differences will help explain why a 1 '/»-horsepower router is so much smaller than the 1 '/»-horsepower motor on your table saw. The big table saw motor will deliver that power for hours on end, while the router motor will squeeze it out for about 30 seconds, then die.

Now let's go back to the amperage ratings. An amp is a reflection of power output, even though it is a measure of electrical input. The UL

is an independent testing agency, using uniform methods. Its ratings will be consistent from brand to brand and model to model. So if you want to compare the power output of one brand of router to another, compare their amperage ratings.

Here's an example of what you'll find:

• Black & Decker's model 3310, rated at 1 Vi hp, draws 8 amps.

• Bosch's model 1602. rated at V/i hp, draws 9 amps.

• Ryobi's R-230 model, rated at 1 Yi hp, draws 9.5 amps.

• Porter-Cable's model 690, rated at \Yi hp, draws 10 amps.

You would probably be justified in concluding that the Porter-Cable unit is more powerful than the Black <Sr Decker, even though their horsepower ratings are the same. And that the Bosch isn't any more powerful, though it's rated with an extra quarter horse. (However, horsepower differences between two routers of the same amperage rating may result from some design or efficiency advantage. The higher-horsepower router may have a slightly better cooling system—a fan that moves air faster, for example—that allows it to run somewhat longer at some mega-amperage draw than the other.)

An interesting sidelight on amperage ratings is that the biggest

General-purpose routers range in size and power from a small

1-horsepower model (left centcr) through 2-horsepower models to the 3-horsepower, 18-pound production behemoth (far left). Even plunge routers are available in a range of sizes: 1-horsepower (right center),

2-horsepower, and 3'/*-horsepower (far right).

Both the router and the induction motor it rests on are rated at 1 horsepower. The relatively huge induction motor, which powers a dust collector, will run all day, continuously producing its rated horsepower. The much smaller universal motor runs at more than 5 times the speed of the large motor but can produce its rated horsepower for relatively brief spurts when under very heavy load.

Both the router and the induction motor it rests on are rated at 1 horsepower. The relatively huge induction motor, which powers a dust collector, will run all day, continuously producing its rated horsepower. The much smaller universal motor runs at more than 5 times the speed of the large motor but can produce its rated horsepower for relatively brief spurts when under very heavy load.

routers may actually be slightly underrated. Though testing may demonstrate that the router could be rated at 17,18, or even 20 amps, the maker rates it at 15 amps and puts a 15-amp cord and plug on it. Why? Because America is wired primarily with 15-amp receptacles (yes. even on 20-amp circuits, and yes, that meets the electrical code). A 20-amp plug won't fit into a t5-amp receptacle. Rather than put a 20-amp plug on a router and consequently limiting severely where it can be used, the manufacturer rates it at 15 amps.

Consider the router work you envision in terms of amps. An 8- to 10-amp router has power enough to drive any bits up to 2 inches in diameter. It will be adequate for trimming cuts—lA inch at a pass. A larger bit or a heavier cut will require more amperage.

Consumer versus Professional

Beyond horsepower and amperage ratings, there's one other crucial matter to consider about a router motor, and that's whether it is what is called a consumer-grade unit or a professional-grade one.

Compared to their consumer counterparts, professional-grade routers arc designed to be more powerful, last longer, and perform better under stress. The motor in this router, for example, must be able to handle sustained use and heavy loading, even overloading. So it is constructed differently than one in a consumer model. The differences begin with the materials and how they are used.

Copper and aluminum can both be used as electrical conductors. Of the two, copper is by far the more efficient. A motor with copper windings will provide more power than a similarly sized motor with aluminum windings. So without increasing the physical size of the motor, just by using copper, the tool engineer can design more power in. And because copper is more expensive and heavier, he designs in more cost and weight.

Want more power? It's in the windings. The greater the volume of windings, the more power the motor pours out. And the heavier it will be. Asked to test routers for their power output, an engineer 1 know suggested simply weighing them. "The heaviest one will probably be the most powerful.'' he explained. It's all in the windings.

Heat buildup is concomitant to hard, sustained use. but heat's a motor killer. The designer does anything he can to make the professional unit more heat-resistant. A high-grade, heat-resistant insulation is used on the wires. Then, after the armature and the commutator arc wound, a heat-resistant resin is dripped into the windings. Capillary attraction pulls the resin into the coils, completely coating every strand and bonding all into a single unit. The resin provides additional benefits: It keeps dust from infiltrating the windings, and it keeps ever)' strand in place, preventing shorts as the armature spins at 22,000 rpm.

A major source of heat in a motor is arcing, which occurs as the electricity passes from the brushes to the commutator. The commutator is made up of copper bars encircling the armature and connected to the windings. The bnishes are pieces of carbon that convey electricity from the power source—your shop outlet—to the commutator. One brush passes the power into a commutator bar. The power flows through the bar into the windings, then into a bar opposite the first. From there, it passes into the second brush, completing the circuit.

To reduce the arcing, the number of commutator bars is increased, and the brushes are positioned more precisely. In addition, the armature is slung in ball bearings, rather than sleeve bearings. The ball bearings not only last longer, they reduce friction and, by virtually eliminating vibration and lateral movement between the commutator and the brushes, they further reduce arcing.

The final heat-reduction measure taken in a professional-grade motor involves the fan. Most consumer-grade routers have stamped-steel faas. They are cheap to make, but they arc pretty frail. When a blade snaps off at 22,000 rpm. you can imagine what it docs inside the motor housing.

The better router has a heavy cast-aluminum or high-tech plastic fan. It moves lots of air very efficiently and is unlikely to break.

Though all these features arc concealed inside the motor housing, and you can't sec them, they'll be clearly evident. There's something unmistakably substantial about a professional-quality router. Something tactile.

THE COLLET

The typical home-shop router weighs about 7 or 8 pounds. Its collet probably weighs less than an ounce. For that 7-pound router to function the way its maker intended, that teeny part has to be virtually perfect. The catalog of routing woes that originate in a worn or dirt)- collet is short but damning. And unfortunately, some collets seem to have trouble designed into them.

Was this article helpful?

0 0
Woodworking Tools and Installation Tips

Woodworking Tools and Installation Tips

There are a lot of things that either needs to be repaired, or put together when youre a homeowner. If youre a new homeowner, and have just gotten out of apartment style living, you might want to take this list with you to the hardware store. From remolding jobs to putting together furniture you can use these 5 power tools to get your stuff together. Dont forget too that youll need a few extra tools for other jobs around the house.

Get My Free Ebook


Post a comment