Router horsepower vs. shaper horsepower

[Glen Butler]

If you take a router rated and 3 1/4 HP and pit it against a 3HP shaper, its no contest. Why? I know that windings can either allow for more speed or more torque, but is this the entire story or is there more to it?

[John Harden]

Probably the biggest difference is that a shaper will have an induction motor, usually running on 220V. These are usually rated at their true horsepower, while routers are universal motors, running on 110V and they always overstate their HP ratings.

You don't get 3 HP out of a 15 amp universal motor operating at 110V. More like 1 HP.

You will get 3 HP out of a 15 amp induction motor operating at 220V.

Lots of other differences, such as speed come in to play as well, but this is a simplified answer.

[glenn bradley]

Routers get rated as universal motors which is I believe the draw at stall(?). Most shapers have induction motors like your table saw. Think about the power of your 3HP tablesaw vs. your 3-1/2HP router. To me the HP ratings on shop vacs and routers are just a 'word' used to describe a size of a tool.

[Jeff Bratt]

If you take a router rated and 3 1/4 HP and pit it against a 3HP shaper, its no contest. Why? I know that windings can either allow for more speed or more torque, but is this the entire story or is there more to it?

There is no such thing as a 3+ HP router. Everything with a universal motor (like a router) that plugs into a standard US 120V circuit is less than 1 1/2 HP. See here (http://home.roadrunner.com/%7Ejeffnann/WoodWorking/Shop/HP/Horsepower.html) for more details.

Quick answer - shaper motors have real HP ratings - routers don't.

[Chris Friesen]

Router HP (along with shop vacs and such) are calculated by physically braking the motor and measuring how much power the motor can generate. What they don't say is that if you keep it at that level for any length of time you'll overheat the motor and likely blow a breaker.

A 3HP shaper motor can go all day (or at least at the rated duty cycle) providing full rated power.

[Joe Jensen]

The router is rated as "instantaneous" HP. This really means the effective HP for a brief moment, and I believe it also relies on the spinning mass of the rotor's momement. As others said, the max continuous HP you can get from a 110V 15A outlet is a little less than 1.5HP.

Real world, motors are around 60 efficiency. Some of the best are a little over 80%. At 110V and 15A, a normal outless is 1650 watts. At 60% efficiency, that's 990 watts of output from the motor, or 1.32HP.

Any spec above that is a lie

[Jim O'Dell]

Just to add...I believe power is more than just HP. Torque has to come into play at some point, just like in cars and trucks. I'd bet that the difference in torque between a shaper motor and a router motor would be huge. The mass and bigger windings should all add to that. Just speculation on my part. Jim.

[Chip Lindley]

We accept the *fact* that a Porter Cable 7518 router @ 15A is *3-1/4 hp.* 12A routers are in the *2-1/4 HP* range. P-C 690 motors @ 11A are generally referred to as 1-1/2 HP. But the same motor on the 693 plunge is 1-3/4 HP!!

It's all a bit of advertising hype, started (IMO) by Sears back in the '70s. It has escalated since. Not only with universal motors of routers or shop vacs, but also induction motors of table and radial arm saws. Honest 3/4 HP motors (8 or 9A @ 115V) on 10" RAS's were emblazoned with *2.5 HP* (developed horsepower in very tiny letters) An honest 1 hp/115V motor draws about 13A. My 3hp/230V Baldor tablesaw motor draws 15A. (that would be 30A at 115V) Huge difference between that 3 HP motor and P-Cs largest 3-1/4 HP router!

Use tool amperage as the rule of thumb for a tools power; not ad hype. Regardless of how electrical engineers measure a tools real horsepower, we can use the amp rating for comparison between brands and models.

[Van Huskey]

Just to add...I believe power is more than just HP. Torque has to come into play at some point, just like in cars and trucks. I'd bet that the difference in torque between a shaper motor and a router motor would be huge. The mass and bigger windings should all add to that. Just speculation on my part. Jim.

Even assuming horsepower was actually the same the torque of the shaper would be higher since the shaft speed is much lower than the router. This is similar to the fact F1 cars produce much less torque (due mainly to the fact they only displace 2.4L) compared to Nascar engines (~5.7 L) but the F1 engines produce more HP due to the fact they spin about 10K rpm faster than the Nascar engines. Interestingly, the max rpm of a Nascar engine is similar to a shaper and the max RPM of a F1 engine is near that of a router. Torque is actually much less of an issue with routers/shapers since they are not judged by their ability to accelerate the bit but the ability to keep the bit spinning at a set speed, in this application HP is definately king.

Bottom line IF horsepower were really equal the router would have signficantly less torque but in a very general sense the router could do just as much work as the shaper due to its higher operational speed. Further the shaper would have even more torque at 10,000 rpm than a router at 10,000 rpm and by definition produce more horsepower at those speeds. The latter is the reason that even if a router produce 3hp at 25,000 RPM it would still have much less horsepower and torque at 10,000 rpm, the shaper would be rated at about 10,000 rpm so when spinning a panel raising bit the shaper could do much more work at 10K even if the router was properly rated at 3hp at 20-25K rpm.

[Rod Sheridan]

Just to add...I believe power is more than just HP. Torque has to come into play at some point, just like in cars and trucks. I'd bet that the difference in torque between a shaper motor and a router motor would be huge. The mass and bigger windings should all add to that. Just speculation on my part. Jim.


Hi Jim, if we had a router that was rated 1 HP at 9,000 rpm, and a shaper motor that was 3 HP at 3,000 rpm the torque available at the shaper motor would be 9 times that of the router motor. (3 X HP, 1/3 speed).

Now if we put the above shaper motor in a shaper, with a 1:3 drive ratio to get 9,000 RPM on the shaper spindle, the shaper torque would now only be 1/3 of the motor torque. (1:3 drive ratio).

Fortunately the shaper motor started out at 9 X the torque so it's still 3 X the torque at the spindle speed.

It really is the power that allows the work to be done at different rates.

There are two main issues with the shaper VS router

1) More HP on the shaper

2) Larger cutter diameter, better cutting geometry

That's why people who are familliar with a router table are amazed when they see or use a shaper for the first time, they really are different.

Regards, Rod.

[Van Huskey]

Use tool amperage as the rule of thumb for a tools power; not ad hype.

Even though this is a better estimate of horsepower than the ratings applied to universal motors for sales hype, it does a disservice to higher quality motors (like Baldor) because of their higher effeciency. But in the end I do agree that current draw is a better indicator of power than listed HP ratings.

[Jeff Bratt]

Hi Jim, if we had a router that was rated 1 HP at 9,000 rpm, and a shaper motor that was 3 HP at 3,000 rpm the torque available at the shaper motor would be 9 times that of the router motor. (3 X HP, 1/3 speed).

Now if we put the above shaper motor in a shaper, with a 1:3 drive ratio to get 9,000 RPM on the shaper spindle, the shaper torque would now only be 1/3 of the motor torque. (1:3 drive ratio).

Fortunately the shaper motor started out at 9 X the torque so it's still 3 X the torque at the spindle speed.

HP is torque x speed. More torque, or faster, or both = more HP. (I'm talking real HP, not fake router/shop vac HP.) So your example is quite accurate - if the speeds are equal, then the 3 HP motor can deliver 3 times the torque and 3 times the HP compared to the 1 HP motor. It would be that simple - if HP numbers were accurate.

[Jeff Duncan]

Yeah all that stuff is fine, but 2 observations.

1st, there are 3 hp routers with true 3 hp motors.....just not handheld.

2nd and more importantly, when you buy a shaper you can start off with 5 or 6hp or even larger.....your not going to find a 6 hp handheld router;)
good luck,
JeffD

[Jeff Monson]

So will a 1.5 hp shaper handle a raised panel bit better than a 3hp router will?

I have been looking at the jet 1.5 hp shaper because of its compact size, is this enough shaper to handle most things a hobbyist will throw at it?

[Rod Sheridan]

Jeff, if you mean bit, as in router bit, the 1.5 HP shaper will be superior to a 3HP router for a few reasons.

- solid, flat table

- better fence with split design

- bit elevation built in

However, if you use router bits you're missing most of what a shaper can do

- run forward and reverse so you can flip cutters over so you're always cutting with the grain

- ability to use insert heads with HSS knives, economical, superior finish in solid wood

- ability to stack cutters

- larger diameter cutters for better cutting geometry

The 1.5HP shaper will be small for running full size cutters, I would strongly recommend a 3HP machine.

I doubt if the floor space is different from a router table.

I think you're smart to look at shapers, they're versatile, powerful and capable in ways that have to be seen to be appreciated.

Regards, Rod.

[Rob Lindquist]

I know this is a horse power post, and I don't want to turn it into a shaper vs. router table post. But the last couple posts are heading that way.
Can most shapers turn a high enough RPM to run router bits? I have a Jet shaper, and a router table with a PC high horsepower variable speed router. The router table gives better cuts than the shaper using router bits in each. Shaper cutters are more expensive and for a hobby of small job it may not be economical to buy shaper cutters. That said I need to look into HHS cutters mentioned. I only have a few sets of shaper cutters, all carbide and those do shine.

[Homer Faucett]

First, remember that most routers spin a bit between 12,000-20,000 rpm, versus a shaper running at about 10,000 rpm. For that reason, most agree that running small diameter router bits in a shaper don't result in as good a finish.

Further, remember that router tooling, in general, is generally more economical than shaper tooling, and, although you can spend as much as you want on a router and table setup, you can put one together with a 2-3 hp plunge router and a plate/table setup for much less than most shapers, regardless of the price comparisons you see that tell you that you need a router lift and oodles of accessories to get started.

This article gives a good, generally unbiased view of the difference between the two: http://benchmark.20m.com/articles/ShaperVersusRouter/shaper_versus_router.html .

I think the cost estimate it gives for routers is high, as I put together my first router table with a Ryobi 3hp plunge router and Rockler router table top for about $180 total (that included the feather boards, fence, and router plate). I still use that setup as my primary router table for most activities. I put together a second, identical setup a few years later for about $100 total when I got a good deal on another Ryobi router and found a clearanced router table top. I have occasionally seen a used 3hp shaper around here go for $500, and once, saw one sold for $300. I called on both within the hour they were listed, and they were gone.

Additionally, regardless of the comparison between the induction/universal motors that talk about actual power, I have never seen anyone post that they were really pleased with a 1.5 hp shaper. If you do production work with big profiles, I have no doubt that a shaper is the answer, but I've never seen anyone recommend buying a 1.5 hp shaper, and I've seen several say they were disappointed when they did buy one.

If you are a hobbyist doing limited runs and want to have the flexibility of multiple profiles for less money, you begin to understand why most people around here have a router in a table.

Can you get a good shaper setup with profiles on the cheap? Probably, if you look really hard. Do you need one? I guess that depends on your situation. Good luck!

[Van Huskey]

I know this is a horse power post, and I don't want to turn it into a shaper vs. router table post. But the last couple posts are heading that way.
Can most shapers turn a high enough RPM to run router bits? I have a Jet shaper, and a router table with a PC high horsepower variable speed router. The router table gives better cuts than the shaper using router bits in each. Shaper cutters are more expensive and for a hobby of small job it may not be economical to buy shaper cutters. That said I need to look into HHS cutters mentioned. I only have a few sets of shaper cutters, all carbide and those do shine.


Depending on the bit they can be equal or the shaper can be behind on quality given the same feed rate. If it is a panel raising bit and both are runnng at 10K then the cut should be the same except for the shapers other inherent strengths, but just based on speed they will be the same. With smaller bits that can be spun at higher speeds the router will have an advantage given equal feed rates. You can use Freud's quadra-cut bits to effectively double the speed of the cut and allow the shaper to give high quality cuts at the same feed rate as a router with a 2 cutter bit.

In the end you have to view a router and shaper as two different machines with different tasks, though they do overlap some one wll not completely do the job of the other. Routers are much more versatile and one reason you usually see several in different configurations in small shops. I have 7 routers and always feel like I need more, I might want a bigger shaper but I can't imagine wanting more shapers even if I had the money and room.

[Jeff Monson]

Jeff, if you mean bit, as in router bit, the 1.5 HP shaper will be superior to a 3HP router for a few reasons.

- solid, flat table

- better fence with split design

- bit elevation built in

However, if you use router bits you're missing most of what a shaper can do

- run forward and reverse so you can flip cutters over so you're always cutting with the grain

- ability to use insert heads with HSS knives, economical, superior finish in solid wood

- ability to stack cutters

- larger diameter cutters for better cutting geometry

The 1.5HP shaper will be small for running full size cutters, I would strongly recommend a 3HP machine.

I doubt if the floor space is different from a router table.

I think you're smart to look at shapers, they're versatile, powerful and capable in ways that have to be seen to be appreciated.

Regards, Rod.

Sorry Rod, should have been more clear on my question.

What would perform better and make a nicer cut?

1. A 3hp router, table mounted, doing rasied panel operatioins (stile cuts, rail cuts and raising panels)

2. A 1.5 hp shaper, doing the exact same operation, except using 3/4" bore shaper cutters instead of the router bits.

Also will a 1.5hp shaper handle raising panels in one cut?

[Bill Orbine]

Sorry Rod, should have been more clear on my question.

What would perform better and make a nicer cut?

1. A 3hp router, table mounted, doing rasied panel operatioins (stile cuts, rail cuts and raising panels)

2. A 1.5 hp shaper, doing the exact same operation, except using 3/4" bore shaper cutters instead of the router bits.

Also will a 1.5hp shaper handle raising panels in one cut?


Answer: Shaper..... hands down (oh yeah, and away from the cutters).

[David DeCristoforo]

"For that reason, most agree that running small diameter router bits in a shaper don't result in as good a finish. "

Most may agree but that does not make them correct. This is a myth that has been dispelled many times. Think of it in terms of the number of cuts per minute and you will see that simply slowing the feed rate will compensate for the shaper's slower cutter speed.

[Glen Butler]

Wow I didn't know the thread had blown up like this.

Torque and Horsepower are two different animals. Basically Torque is low end power and Horsepower is high end power. The amount of torque and horsepower is all dependent on the number of windings. Fewer windings will cause the motor to spin faster giving it more horsepower, it will also draw more amps. More windings will give it more torque but it will spin slower.

As misunderstood by others above, rotational mass has nothing to do with torque, but it is an added benefit to a shaper, for balancing, vibration, and quality of cut.

[Glen Butler]

Sorry Rod, should have been more clear on my question.

What would perform better and make a nicer cut?

1. A 3hp router, table mounted, doing rasied panel operatioins (stile cuts, rail cuts and raising panels)

2. A 1.5 hp shaper, doing the exact same operation, except using 3/4" bore shaper cutters instead of the router bits.

Also will a 1.5hp shaper handle raising panels in one cut?

Shapers have a much better cutter head geometry. They will always cut nicer than a router.

I doubt a 1.5HP shaper will handle panel raising in one cut. Granted it all depends one feed rate, but for cutter life it is important to be able to cut a large enough chip to keep the carbide cool. My 3HP PM-25A shaper can cut a 1.5" deep RP profile including the back cut, in hickory and maple, but you can tell that the motor is working.

[Rich Engelhardt]

Use tool amperage as the rule of thumb for a tools power; not ad hype. Regardless of how electrical engineers measure a tools real horsepower, we can use the amp rating for comparison between brands and models.
+1 to that idea.

Amp rating has a lot more use than hp - especially if the tool is going to live at the end of any type of extension cord.

In my case, I bypassed the 15 amp routers in favor of a 13 amp (Freud 1700) simply because the 13 amp is more "extension cord friendly".

Same w/my IR compressor, my recip saw, a TS55 EQ, and a whole host of others.

[Rod Sheridan]

Jeff, you received good answers above.

1.5HP is too small for a single pass raised panel cut using a shaper cutter (Large cutter diameter).

Do yourself a favour and get a 3HP machine, it doesn't take up more flooe space than a router table, and you can bolt a stock feeder to it.

I've found that's it's least expensive to get the correct tool first time, and avoid the future replacement expenses.

Regards, Rod.

P.S.

http://www.sawmillcreek.org/showthread.php?p=1363398#post1363398

Please read the posting from Van Huskey regarding a possible sale price of the Jet 3HP shaper. That looks like a great price to me.

[Jay Allen]

Why would you run an air compressor on an extension cord? Get a longer air hose, it's a win-win situation. There is no loss of performance and you are farther away from the noise.

Second, although horsepower and torque are talked about together and measured from one another, they are very different.

Torque is twisting (rotational) force, but it does not require movement.
You can apply 50 ft/lb of torque to a bolt which is already tighter than that....and nothing happens. You are still applying torque however.

Horsepower is a measurement of work performed. IE, a weight moved a specific distance in a certain time. Horsepower requires movement.

As stated by Van Huskey, amp draw is a better gauge of comparing machines, it is not the whole story either. It just tells you how much electricity is consumed, not what the machine actually does with that power. More efficient motors do more w/o wasting that power by making heat. Reak hands-on use of the machine well tell you far more.

[Jeff Duncan]

Sorry Rod, should have been more clear on my question.

What would perform better and make a nicer cut?

1. A 3hp router, table mounted, doing rasied panel operatioins (stile cuts, rail cuts and raising panels)

2. A 1.5 hp shaper, doing the exact same operation, except using 3/4"
bore shaper cutters instead of the router bits.

Also will a 1.5hp shaper handle raising panels in one cut?


That's a bit too vague of a question! What kind of router in what kind of table with what kind of tooling vs what kind of shaper? I'd be willing to bet there are some pretty hyped out router tables out there that would kick the pants off most of the small 1-1/2 hp shapers.
Here's a generic answer. A quality shaper will give a better quality of cut.....why? Well a good shaper will have a much more robust spindle meaning less run-out under load than the router. Also the tooling can be a larger diameter which also helps with finish quality. An even larger shaper will provide a better quality of finish than a smaller shaper, b/c it utilizes an even larger (more stable) spindle and even larger tooling.
But these are all just generalizations. I use a 5 hp shaper with 1-1/4" spindle to do my sticking and coping cuts. I also have a 3 hp tilting shaper which is a bit more flexible as it has a router collet. I used it with a router bit to make up a batch of ultralight mdf raised panels this week. The reason I used a router bit is b/c it was a small job, only 1/2 a kitchen, and required an unusual raised panel. I had a choice between a $30 router bit or a set of custom knives which would have cost maybe $200. I used the router bit and can guarantee nobody would be able to tell the difference in the finished product. Now if I had to do the same profile in hardwood I may have made a different choice.
I also have a router table that gets plenty of use. If I had the choice between a table top 1-1/2 hp shaper and my router table I'd stick with the table. If it was a beefier freestanding 1-1/2 hp shaper that seemed like a decent quality machine???
good luck,
JeffD

[Jeff Duncan]

I know this is a horse power post, and I don't want to turn it into a shaper vs. router table post. But the last couple posts are heading that way.
Can most shapers turn a high enough RPM to run router bits? I have a Jet shaper, and a router table with a PC high horsepower variable speed router. The router table gives better cuts than the shaper using router bits in each. Shaper cutters are more expensive and for a hobby of small job it may not be economical to buy shaper cutters. That said I need to look into HHS cutters mentioned. I only have a few sets of shaper cutters, all carbide and those do shine.


Rob, I think your problem is more in tune to the particular shaper your using. If your getting better cuts with a router there is something wrong with your shaper and better tooling will not fix it. At the very least the quality of cuts should be identical, with the edge definitely going to the shaper. Now I'm assuming your using larger bits, (smaller bits will work but not as well b/c of speed and diameter of the tooling) like raised panel bits and the like. Your shaper should run larger bits smoother than the router can.
I make it a habit to run anything larger than roughly an inch diameter on my shaper. Anything smaller gets put on the router table. This is a generalization as it really depends on circumstances.
HSS knives are great, but probably not the answer for the average hobbiest. HSS is great b/c you can have the knives ground to your own profiles, and it leaves a great finish. You also need to have heads to mount the knives though, more $$$. For most profiling your going to be better of just buying off-the-shelf carbide as it lasts longer and will be much cheaper. If you start getting to the point where you want to buy a head and do custom profiles plan carefully. Most pro shops and heavy shapers run larger dia spindles 1-1/8" - 1-1/4". You have to decide if you want to (or may want to in the future), upgrade your shaper to a larger spindle and buy larger heads. Or buy the smaller 3/4" heads for your Jet (I'm assuming the Jet is 3/4" spindle right?), which may not be the best investment long term.
good luck,
JeffD

[Homer Faucett]

"For that reason, most agree that running small diameter router bits in a shaper don't result in as good a finish. "

Most may agree but that does not make them correct. This is a myth that has been dispelled many times. Think of it in terms of the number of cuts per minute and you will see that simply slowing the feed rate will compensate for the shaper's slower cutter speed.

Well, I guess it's all in how you look at it. It's no myth that when you run two identical pieces; one through a shaper at 10,000 rpm and one through a router at 20,000 rpm, that all things being equal, the router will have double the number of cuts per minute and double the number of cuts per linear foot.

Sure, if you slow the feed rate of the shaper by half that of the router, you can get the same number of cuts per linear foot. However, I thought this was supposed to be an even comparison, not one where we stacked all the variables in favor of the shaper.

After all, if it's fair to point out that you shouldn't do raised panels on a router in one pass, but you can do that on a shaper, why can't it be pointed out that you'll get a better result on a router in one pass using small bits than on the shaper? It's clear that you either have to take two passes with the shaper or slow the feed rate down by half to get the same number of cuts.

On the flip side, I could point out that it's a my that you can't get great raised panels on my router in one pass--you just have to clip all the edges on the table saw first to remove most of the material.

[Rich Engelhardt]

Why would you run an air compressor on an extension cord?
There's times when I have to.
Not often, but, often enough.

Last summer I packed the compressor in the car, drove 57 miles to where I was going to use it and found out all I had was a 10 foot hose and a 25 foot extension cord.

I could have blown off the whole day - or wasted a couple of hours either driving back home or driving around trying to find a HD or Lowes and dropped $20 for a cheap useless hose.


@ home or closer to home?
Hey, I'm with you all the way. It's better to add hose.

But - I only have so much space in the car or van to haul tools so I try to keep things on the simple side.
It the price paid for having a rental so far from home base & a tenant that won't tell us what needs fixed so we have to take a wild guess at what equipment we'll need.

[Jacob Reverb]

I think it mainly has to do with the way universal motors and induction motors work, and how manufacturers rate them.

The more you load a universal motor (i.e., slow it down), the more torque it develops, the more current it draws, and the more "developed" horsepower it puts out (and the hotter the windings get) – and manufacturers often rate universal motors on "peak developed horsepower."

I think the way they get the 3-1/4hp rating on a 110V/15A router is to load the motor until just before it stalls, and measure the horsepower there. If it's putting out 3-1/4 hp at that point, you can bet that:

a) it's drawing a heck of a lot more than 15A (laws of physics and all that), and
b) it won't keep putting out that much power for long before burning up.

An induction motor rated at 3-1/4 hp puts out a max of 3-1/4 hp, but it won't hurt the motor to do so for extended periods. And if it has a continuous-duty rating, you can get 3-1/4 hp out of it all day long.

More here (http://books.google.com/books?id=WFGQCXGupDcC&pg=PA14&lpg=PA14&dq=%2B%22universal+motor%22+%2B%22horsepower+ratin g%22&source=bl&ots=RqPPiKzLZ0&sig=pqwXhKUNO48HNysellfJEHdEeDY&hl=en&ei=VDSYS6eZDM_DlAf0zKS9DQ&sa=X&oi=book_result&ct=result&resnum=9&ved=0CCcQ6AEwCA#v=onepage&q=%2B%22universal%20motor%22%20%2B%22horsepower%20 rating%22&f=false).

[Jeff Bratt]

I think it mainly has to do with the way universal motors and induction motors work, and how manufacturers rate them.

The more you load a universal motor (i.e., slow it down), the more torque it develops, the more current it draws, and the more "developed" horsepower it puts out (and the hotter the windings get) – and manufacturers often rate universal motors on "peak developed horsepower."

I think the way they get the 3-1/4hp rating on a 110V/15A router is to load the motor until just before it stalls, and measure the horsepower there. If it's putting out 3-1/4 hp at that point, you can bet that:

a) it's drawing a heck of a lot more than 15A (laws of physics and all that), and
b) it won't keep putting out that much power for long before burning up.

An induction motor rated at 3-1/4 hp puts out a max of 3-1/4 hp, but it won't hurt the motor to do so for extended periods. And if it has a continuous-duty rating, you can get 3-1/4 hp out of it all day long.

More here (http://books.google.com/books?id=WFGQCXGupDcC&pg=PA14&lpg=PA14&dq=%2B%22universal+motor%22+%2B%22horsepower+ratin g%22&source=bl&ots=RqPPiKzLZ0&sig=pqwXhKUNO48HNysellfJEHdEeDY&hl=en&ei=VDSYS6eZDM_DlAf0zKS9DQ&sa=X&oi=book_result&ct=result&resnum=9&ved=0CCcQ6AEwCA#v=onepage&q=%2B%22universal%20motor%22%20%2B%22horsepower%20 rating%22&f=false).

One horsepower is one horsepower - whether generated by an induction motor or a universal motor. ALL motors are rated by putting a load on them, then measuring torque, current draw, and speed. Induction motors are generally rated accurately - especially ones from quality manufacturers like Baldor, Leeson, and others. Many induction motors also include a service factor rating as part of their specifications, that quantifies how much over the rated power the motor can safely handle for short periods of time.

Small universal motors are routinely and flagrantly overrated. The maximum power that is available from a US 120V 15A circuit is 1800 watts. If a motor was 100% efficient - and none in this size come anywhere close - that would be around 2.4 HP. If we quite reasonably estimate the efficiency of a universal motor at 50%, that puts the maximum at 1.2 HP when running on the standard 15A circuit.

You are correct that a motor - induction or universal - can momentarily produce more torque than its rating. Induction motors often stall at around 200% of rated torque. But this is also assuming that electrical circuit is capable of supplying twice the rated motor current. Universal motors produce their highest torque at low speeds - right before stalling. But because the speed is also slower, this is not necessarily their highest HP. Remember, HP is torque x speed. Also, motor control can become very unstable slow speeds. Typical router speeds are between 8,000 and 25,000 RPM. So measuring the torque of a router at even 500 RPM is useless.

Starting currents - in both induction and universal motors - are much greater than the nominal 15A circuit breaker rating. But these only last for a second or two - or else the breaker trips. (Note that induction motors don't inflate their ratings by a factor of 5 or 10 because of these high starting currents). So maybe a big router could momentarily produce enough torque to "develop" more than 2 "peak HP" right before the breaker trips or the motor burns out. Or, if you measure the locked rotor current, you could "calculate" the HP to be some large number - but if the rotor is stalled, then there is really NO power being generated, because there is no motion.

Bottom line - ANY motor running on a 120V, 15A circuit is 1.5 HP or less. Universal motors are less - because they have even lower efficiencies than induction motors. A HP is a HP - 33,000 ft lb per minute, no matter whether produced by induction motor, universal motor, windmill, water, or a horse.

Regarding your reference, Tauton is unwilling to call out the manufacturers that support them by pointing out that there is really no such thing as "peak horsepower". Rating a router based on how much torque it can produce for 1/2 second right before burning up is, very simply, a lie. If the operation of a router only lasted for 1/2 second - maybe that would be a reasonable measurement. But since routers run for a minute, or 5, or 10, the only legitimate HP measurements are how much power the motor can generate while being used for its intended purpose.

So I'll reiterate - there is no such thing as a 3 HP router, and especially nothing even close to a 6 HP shop vac. People may have a skewed notion of differences between motors because they have been consistently lied to about the capabilities of these small motors for somewhere close to 40 years now.

[Joe Jensen]

One horsepower is one horsepower - whether generated by an induction motor or a universal motor. ALL motors are rated by putting a load on them, then measuring torque, current draw, and speed. Induction motors are generally rated accurately - especially ones from quality manufacturers like Baldor, Leeson, and others. Many induction motors also include a service factor rating as part of their specifications, that quantifies how much over the rated power the motor can safely handle for short periods of time.

Small universal motors are routinely and flagrantly overrated. The maximum power that is available from a US 120V 15A circuit is 1800 watts. If a motor was 100% efficient - and none in this size come anywhere close - that would be around 2.4 HP. If we quite reasonably estimate the efficiency of a universal motor at 50%, that puts the maximum at 1.2 HP when running on the standard 15A circuit.

You are correct that a motor - induction or universal - can momentarily produce more torque than its rating. Induction motors often stall at around 200% of rated torque. But this is also assuming that electrical circuit is capable of supplying twice the rated motor current. Universal motors produce their highest torque at low speeds - right before stalling. But because the speed is also slower, this is not necessarily their highest HP. Remember, HP is torque x speed. Also, motor control can become very unstable slow speeds. Typical router speeds are between 8,000 and 25,000 RPM. So measuring the torque of a router at even 500 RPM is useless.

Starting currents - in both induction and universal motors - are much greater than the nominal 15A circuit breaker rating. But these only last for a second or two - or else the breaker trips. (Note that induction motors don't inflate their ratings by a factor of 5 or 10 because of these high starting currents). So maybe a big router could momentarily produce enough torque to "develop" more than 2 "peak HP" right before the breaker trips or the motor burns out. Or, if you measure the stalled rotor current, you could "calculate" the HP to be some large number - but if the rotor is stalled, then there is really NO power being generated, because there is no motion.

Bottom line - ANY motor running on a 120V, 15A circuit is 1.5 HP or less. Universal motors are less - because they have even lower efficiencies than induction motors. A HP is a HP - 33,000 ft lb per minute, no matter whether produced by induction motor, universal motor, windmill, water, or a horse.

Regarding your reference, Tauton is unwilling to call out the manufacturers that support them by pointing out that there is really no such thing as "peak horsepower". Rating a router based on how much torque it can produce for 1/2 second right before burning up is, very simply, a lie. If the operation of a router only lasted for 1/2 second - maybe that would be a reasonable measurement. But since routers run for a minute, or 5, or 10, the only legitimate HP measurements are how much power the motor can generate while being used for its intended purpose.

So I'll reiterate - there is no such thing as a 3 HP router, and especially nothing even close to a 6 HP shop vac. People may have a skewed notion of differences between motors because they have been consistently lied to about the capabilities of these small motors for somewhere close to 40 years now.


Well said. I always wonder why the makers of these small motor tools are allowed to "exagerate" in this way. Especially the shop vacs. Does anyone know who controls this in the govt?

[Jeff Bratt]

Well said. I always wonder why the makers of these small motor tools are allowed to "exagerate" in this way. Especially the shop vacs. Does anyone know who controls this in the govt?

I know of no mandated standards concerning HP ratings of motors. Electrical codes govern other safety requirements, but power ratings should fall under the general jurisdiction of the Federal Trade Commission "Truth in Advertising" rules. This issue should be quite simple - advertising copy should just say what's true. We can all see how well that's working...

As far as I can tell, this debacle all started back in the 1970s when a large retailer started "inflating" the HP ratings of the tools it was selling to make them sound better then they actually were. Soon other manufacturers and retailers simply followed along. First a 3/4 HP motor became a 1 HP motor, then a 2.5 "peak HP" motor, then up to 4 "max developed HP" - where does it end???

[Mike Henderson]

Many induction motors also include a service factor rating as part of their specifications, that quantifies how much over the rated power the motor can safely handle for short periods of time.
I think "service factor" is defined as a factor times the rated power of the motor, at which the motor can operate, and results in a 10*C rise in temperature, probably at some defined ambient temp.

So if you have a 2HP motor with 1.2 service factor, you can extract 2.4HP out of that motor but the temperature will rise by 10*C. That temperature rise will halve the life of the motor (if you operated continuously at the power level). So there's no free lunch.

Mike

[Randy Smith]

One thing that has been touched on by a couple people regarding router table vs shaper - I think bit tip speed is a big contributor to cut quality. I have a 3hp shaper that has a router collet that can be used with it. The shaper turns at 10,000 rpm which is lower than a router. With the smaller diameter of the router bit (compared to shaper cutters) and the lower shaper speed, you end up with a much lower tip speed. I just ran a bunch of shoe mold through the shaper with a round-over router bit and even with all kinds of feather boards holding everything in place, there was a fair amount of tear out.

So the lesson for me is that I need a basic router table for some of the small stuff I do, and I need to buy shaper cutters for common profiles that I make on a regular basis.

[Dec Olores]

The router is rated as "instantaneous" HP. This really means the effective HP for a brief moment, and I believe it also relies on the spinning mass of the rotor's momement.

Both induction motors and universal motors are rated, by specification, at their maximum power. The difference is, as you note, that universal motors (e.g. the router motor) must store energy to provide the peak HP and thus cannot sustain it for very long, while the induction motor (e.g. shaper) can supply it's rated power indefinitely.

A lot of woodworkers seem to think that peak HP ratings are deceptive, but it's really not. It's just that universal motors are rated a little differently than induction motors, by specification and code. Comparing them directly isn't really a valid comparison, more of an "apples and oranges" comparison, which is what I suspect leads to the confusion.

[Dec Olores]

W

Use tool amperage as the rule of thumb for a tools power

The problem with using amperage is that the efficiency of the motor is often not known. Efficiencies can be very low, particularly on a low end motor. Thus, a 10 A motor on a low end imported tool may really be 1/2 HP or less, rather than the 1 HP the current suggests.

[Joe Jensen]

Both induction motors and universal motors are rated, by specification, at their maximum power. The difference is, as you note, that universal motors (e.g. the router motor) must store energy to provide the peak HP and thus cannot sustain it for very long, while the induction motor (e.g. shaper) can supply it's rated power indefinitely.

A lot of woodworkers seem to think that peak HP ratings are deceptive, but it's really not. It's just that universal motors are rated a little differently than induction motors, by specification and code. Comparing them directly isn't really a valid comparison, more of an "apples and oranges" comparison, which is what I suspect leads to the confusion.

Yes, I understand completely. Seems a little silly to rate the two so differently. Especially since the way universal motors are rated is essentially useless. When I see something like that I smell lobbiest.

[Rick Fisher]

Mafell makes a router that draws 2200W.. As does Festool.
They are likely the most powerful hand held routers made, but neither would compare to a 3hp shaper..

I have a PC 7518 in my table right now, and while I am the first to admit that its not in the same league as my shaper, its a heck of a capable tool, and the cutters are much cheaper than my shaper cutters..

Try to imagine a router with a motor big enough to compare to a stationary shaper.. it would be brutal to lift and move..

Pin Routers are often 7.5hp .. They spin at 20K and are really 7.5hp .. they usually weigh at least a 1/2 ton..