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Induction vs Universal Motor and Shaper vs Router

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Forum topic by JakeT posted 09-13-2011 06:15 PM 5309 views 0 times favorited 8 replies Add to Favorites Watch
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JakeT

9 posts in 2491 days


09-13-2011 06:15 PM

Topic tags/keywords: induction universal shaper router

I am aware of some of the functional differences between the two motor types, but no the technical reason the induction generates so much more torque. I read once induction motors are more efficient.

It occurred to me the other day while cutting 3/4×3/8 dadoes using a dado stack on read oak on my 1 1/2 hp contractor saw that this could be done in one pass, while my supposedly 2 1/4 hp router would have needed at least 3 passes to do that depth.

Both pull 13 amps at 110.

Does that mean even a relatively low HP shaper, like 1 1/2 hp, would produce significantly more power than a router, like cutting raised panels in one pass?


8 replies so far

View ajosephg's profile

ajosephg

1878 posts in 3027 days


#1 posted 09-13-2011 06:59 PM

The reason a 3/4×3/8 dado can be cut in one pass on a TS vs many cuts on a router isn’t related to horsepower.

A dado stack has bunches and bunches of cutting surfaces and a big path to conduct heat away from them. They have some time to cool between each time they meet the wood. A router bit has only two cutting surfaces and a somewhat limited cooling path. And, at 25,000 rpm the time between cuts is like zilch.

I don’t have time right now to talk about all the pros and cons of universal and induction motors. Without getting too technical two reasons are:

1. Universal motors are less expensive to manufacture.

2. Universal motors are smaller than induction motors of a given HP, with the caveat that the universal motor is going to have a much higher rpm to develop equivalent HP. (I think)

-- Joe

View PurpLev's profile

PurpLev

8523 posts in 3114 days


#2 posted 09-13-2011 07:09 PM

Since Joe addressed the motors I’ll address your 2nd question:

Yes, a 1.5Hp shaper will have much more torque then your 2.25Hp router and will be able to take deeper cuts = dadoes and raised panels in 1 pass.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View WoodDweller's profile

WoodDweller

36 posts in 1197 days


#3 posted 10-04-2013 11:43 PM

I came across this old post … and might reply as I wondered, and looked, up the same thing. Cant find the reference but …

Induction motors are big and heavy, but quiet and last long. So they are used on big machines like table saws. Universal motors are small and noisy. So they are used on handheld power tools like routers. The horse power rating on the universal motor, mean different things compared to the horse power ratings for induction motors.

If i understood it correctly. The universal motor rating means how much power would be going through the motor just before it self destructs. For induction motors, the horse power rating, is about normal peak power usage. You could keep the motor at this power for more than just a moment, and it wouldnt break.

Cheers

View Loren's profile

Loren

8313 posts in 3114 days


#4 posted 10-05-2013 12:39 AM

There are special router bits that clear chips better you can
get for production router dadoing. They mitigate heat
build-up.

Also, I have a 20,000 rpm router in my shop with an induction
motor. It has pulleys to step up a 3450 rpm motor to 10,000
or 20,000 rpm. It is not a handheld unit, but it is still a router.

I know this is an old thread.

View JustJoe's profile

JustJoe

1554 posts in 1504 days


#5 posted 10-05-2013 12:56 AM

Loren my biggest complaint about routers is the noise. Can you elaborate on this 20,000 rpm induction-motor router please?

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Loren

8313 posts in 3114 days


#6 posted 10-05-2013 01:12 AM

It’s an ru-50 overarm router made by Invicta. It’s still pretty
loud due to the air churning and it has a spindle of course and at
that rpm I expect the bearings may make some noise. It
doesn’t emit the screaming partials hand-held routers do.
I have never stepped outside the shop while it was running,
so I don’t know how the sound carries.

View JustJoe's profile

JustJoe

1554 posts in 1504 days


#7 posted 10-05-2013 01:35 AM

Thanks – I have no neighbors within 1/4 mile, so I can run the planer at midnight with the doors open, but the high-pitch of a router just annoys me to no end.

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jonah

687 posts in 2765 days


#8 posted 10-05-2013 02:58 AM

Your router is not developing anywhere near 2.25HP. It’s physically impossible for a universal motor running on 60hz 120V AC to develop more than about 1.5-1.75HP. Yours, pulling 13 amps, is closer to 1.5HP.

See here:

http://home.roadrunner.com/%7Ejeffnann/WoodWorking/Shop/HP/Horsepower.html

and here:

http://www.kevinsbrady.net/motors.pdf

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