Router 'Power' Question

[Terry Stellman]

I have been looking for a new router for my table. I have been reading all the posts lately about routers and the recommendations for certain horsepower routers being seen necessary for different jobs. This is not a brand specific question but since the 2 1/4 hp routers are 13 amps and the 3 1/4 hp routers are 15 amps, can you really tell that much difference between the two? Unless they are wired differently somehow there should only be a very small difference. Inquiring minds would like to know. Thanks.

Terry

[Matt Ocel]

Terry -

I can't help you out with the 2 3/4 vs 3 1/4.

I can tell you that I went from the PC 1 3/4hp to the PC 3 1/4hp. Absolute world of difference. I have my 3 1/4 mounted in my router table and if PC would have had a bigger one I would have bought that.

You know what everyone is going to say.

B _ _ _ _ _ R is B _ _ _ _ R !

[pat warner]

The issue is momentum, flywheel.
Bigger routers have bigger armatures, more difficult to slow down.
They are better heat sinks, maintain their momentum, use lecktricity more efficiently etc. It's not a horsepower issue directly.

[Terry Stellman]

Thanks Pat. Momentum would be a very good explanation. I have never taken a router motor apart but the size of moving parts would make a difference.

Terry

[Greg Hines, MD]

One thing you need to consider. The amount of power is relative to what you intend to do with it. If you are going to be using large horizontal panel raising bits, or large multiprofile bits, then go for the largest router you can find. If, on the other hand, you are going to be using mostly <1" diameter bits, 2 1/4hp routers are plenty strong for that.

Doc

[Jeff Bratt]

Manufacturers of consumer products have been lying for years about horsepower. By looking at the amperage ratings, you are getting closer to reality. There is actually no such thing as a 3+ HP router. For a real 3 HP motor, open up a cabinet saw and look inside. And you will also find that 3 HP motors run on 240V (or higher).

A general rule of thumb is: at 120V 10 amps = 1HP, at 240V 5 amps = 1 HP. So anything that plugs into a standard wall socket is going to be less than 1.5 HP.
See http://users.goldengate.net/~kbrady/motors.pdf

That said, the bigger routers are usually sturdier - as Pat said - and can handle larger bits, for which you also need slower speeds. Pat (being unusually restrained today) lists several routers on his website that he deems acceptable and details considerations for choosing hand-held and table mounted routers. An excellent resource on things router related...

[Tom Veatch]

...since the 2 1/4 hp routers are 13 amps and the 3 1/4 hp routers are 15 amps, ...

Unless the laws of thermodynamics were repealed while I wasn't looking, you can be assured that a 13amp/120vac motor is going to develop significantly less than (13*120)/746 = 2.1 HP and a 15a/120 motor significantly less than 2.4 HP.

The rules of thumb that Jeff mentioned take into account the electrical and mechanical efficiencies (ALWAYS less that 100%) and give a much better indication of the power you'll actually see at the output shaft. I don't know how manufacturers justify the inflated HP rating you see since they certainly do not reflect the motor output. In some cases, the "advertised power" is computed by using the motor's locked rotor current to calculate wattage and HP. That is absolute BS and in no way represents the full load power the motor will develop.

[Jim Becker]

Yes, you can tell the difference between a 13 amp and a 15 amp machine under the circumstances are more demanding on power...such as swinging large panel cutters in the router table.

[Tom Veatch]

Jeff, thanks for posting that link. I'd never seen it before, but it should be required reading for anyone owning or shopping for any device that contains an electric motor.

(Maybe I like it so much because the author and I are in full agreement. :D)

[J. Z. Guest]

Unless the laws of thermodynamics were repealed while I wasn't looking, you can be assured that a 13amp/120vac motor is going to develop significantly less than (13*120)/746 = 2.1 HP and a 15a/120 motor significantly less than 2.4 HP.

It's not really a lie as much as a ratings game. Universal brush motor products are severely overloaded, and their max. hp is recorded right before they burn out.

Induction motors (such as you'd find on most stationary tools) will run all day every day at their rated hp without damage. I agree that amps is a much better way of looking at it.

[Peter Quinn]

In layman's terms, my 2 1/4HP router is a nice tool that feels like an over grown blender. My 3 1/4 HP router is like a small out board motor with handles. I can definitely tell the difference. Of course I rarely take a blender water skiing and almost never attempt to blend a margarita with an out board motor, they both have their place.

[Brian Weick]

If you plan on doing raised panels or large architectural shaping - that's when the 3-1/4 is a necessity - I would have mixed feelings using a 2-1/4 for a but as large as those I have mentioned.
Brian

[Jeff Bratt]

There are most likely differences between a "13A router" and a "15A router", but performance improvements are due at least as much to a beefier shaft and frame to resist flexing under load, better bearings, and more rotating mass - as they are to 2A more current. It is just this type of thinking that encourages manufacturers to fudge about HP. Even if you accept their inflated ratings, there is not a 45% increase in power going from a 13A (2 1/4 hp) to a 15A (3 1/4 hp) motor. The manufacturers inflate HP ratings because those numbers are what get emblazoned across the advertisements and packaging. And because the FTC has not held them to account.

Yes, this is a "ratings game", but the HP claims are still lies. Since most people don't know the details about horsepower and electricity, the manufacturers (actually the marketers) can get away with it. I'll draw an analogy - these ratings are like driving a car off a cliff, then measuring the speed at 225mph - just before it crashes at the bottom. Everyone would recognize that this rating for the top speed of a car - while containing some small smidgen of reality - was not the truth.

There is one good thing about all this - a real 3 HP motor would be terribly unsafe in a hand-held tool. Way too heavy, and absolutely impossible to control with arm strength alone...

[Robert Payne]

Notwithstanding the hocus-pocus about HP ratings, IMHO it is imperative that the router mounted for raising panels or cutting mouldings or rails and stiles should be a high amperage, variable speed router. Larger bits require reduced rpms and yet still need plenty of power to turn a panel raising bit. I have a Milwaukee 5620 "3-1/2 HP" VS router in my RT and I'm very happy with it.

[Steven Hardy]

Maybe we should start a WORST OFFENDER list of the Inflated Horsepower ratings we come across..the fact that the fine print says "peak hp "dont matter to me.
I vote for my Rigid pro shop vacuum which is 12.0 amp...
but says 6.5 Horsepower prominantly on the label. It sucks nice...but what a crock!
While were on the subject...dont you wish that when magazines do their reviews..they would remove the saw motor,put it in a lab enviornment ,and tell us what the 100 duty cycle HP REALLY is???? (Its not that hard to do.)

[Josiah Bartlett]

If you have a 15 amp router, you aren't going to be able to use it to full effect without a 20 amp circuit and a good heavy extension cord (or none at all). A 15 amp circuit can only provide a 12 amp continuous current.

I wish somebody would offer 240V routers in the US. How great would a real 3 hp router be?

[Jeff Bratt]

Well - no. A 15 amp circuit will provide 15 amps - and more. If your wiring is on the small side, you may get more of a voltage drop at high current draw - and therefore less power delivered to the load (motor).

In actuality a 15 amp circuit breaker can provide much more than 15 A for a short time - to handle inrush currents and other momentary current surges. Illustrative over-current ratings mean a 15 A circuit breaker (without tripping) allows:
30 A - for 15 seconds
60 A - for 2 seconds
90 A - for 1 second
however, at 20.7 A - must trip within 1 hour.

As I mentioned earlier, an actual 3 HP motor in a hand-held tool would be a really bad idea.

[Tom Veatch]

Jeff, I have a sneaky suspicion that what Josiah is referring to is the 80% derating for a NEC 430 motor circuit - which isn't applicable here, anyway.

Your breaker current rating are interesting. You say "illustrative". Are they meant to be ballpark example numbers, or are they hard numbers from some specification. If hard numbers, can you cite the spec. No criticism of the numbers is implied, just a point of interest to me.

[Peter Quinn]

If you have a 15 amp router, you aren't going to be able to use it to full effect without a 20 amp circuit and a good heavy extension cord (or none at all). A 15 amp circuit can only provide a 12 amp continuous current.

I wish somebody would offer 240V routers in the US. How great would a real 3 hp router be?

We do have those here! They're called "Shapers".:)Oh, and I think both bosch and makita make 240V versions you can order via internet, though with present dollar value now is probably not the right time.

[Jeff Bratt]

The numbers I quoted came from here (http://www.vickers-systems.com/pdfs/power/Series160.pdf). Similar "trip curves" from Square D can viewed here (http://ecatalog.squared.com/pubs/Circuit%20Protection/Molded%20Case%20Circuit%20Breakers/Thermal%20Magnetic%20Molded%20Case%20Circuit%20Bre akers/Powerpact%20H-%20and%20J-Frame%20Accessories/0611CT0401R807.pdf) (starting at page 50). There are varying specifications for different applications - but the point is that "normal" circuit breakers will pass multiples of their rated current for a short period of time - without tripping.

[Tom Veatch]

Thanks for the links, Jeff. I knew there was overload tolerance, but other than one empirical, inadvertent test in my shop had no data points on the curve.

[Terry Stellman]

Thanks for the input. I ordered a 3 1/4 hp Triton from Sommerfeld tools today. They have the best price and no shipping. Should work well in the router table.

Terry

[Wayne Cannon]

In addition to power and robustness, for a table application, the size of the opening in the base, and the amount of extension of the collet through the base are factors to consider.

Many routers do not have an opening large enough to clear a panel-raising, or other, large bit which prohibits any application where the bit needs to be lowered below the table top (e.g., for part of the profile or for thinner stock). Look for at least a 3-5/8" diameter base opening (most large router plates and lifts have approx. a 3-5/8" opening).

Many routers also do not have sufficient collet extension to raise a bit past the base, the router-plate thickness (e.g., 3/8"), and the bottom of a sliding jig (e.g., a 3/8"-thick coping-sled base). It also helps with bit changing from above the table. Look for at least 7/8" extension beyond the base.

For example, the old PC 7518, in addition to being a workhorse, has about a 4-1/4" diameter base opening and a 1-1/4" collet extension through the base. The 3-1/4 HP Triton has base opening slightly over 3" (that I've expanded to 3-5/8") and a 7/8" collet extension beyond its base.

[J. Z. Guest]

While were on the subject...dont you wish that when magazines do their reviews..they would remove the saw motor,put it in a lab enviornment ,and tell us what the 100 duty cycle HP REALLY is???? (Its not that hard to do.)

I agree that it is not that hard to do. The problem is that the dynamometers cost thousands of dollars, which would take away from their bottom line.

Most portable power tools burn rather quickly if you continually load them to 100% of their current rating. Intermittant use is one thing that's assumed. (and realistically, in most cases)