# table saw rpm



## papazian (Mar 27, 2010)

I want to buy a 3hp cabinet saw. Some are 3450 RPM and others are 4300 rpm. Are there pros and cons for the rpm of the saw?


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## Ghidrah (Mar 2, 2010)

Thing is they're telling motor RPM but then you can change blade RPM by changing pulley diameter. If the prices are the same or close go with the higher RPM


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## Colt W. Knight (Nov 29, 2009)

Like Ghidrah said, motor RPM doesn't equate blade RPM. Sometimes they use higher or lower RPM motors to compensate for different pully and belt designs to achieve the same blade rotation.


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## knotscott (Nov 8, 2007)

That's honestly a spec I've never even looked at with any of my saws. I'd think setup and blade selection would make a more noticeable difference. Buy the saw and deal you like best.


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## cabinetman (Jul 5, 2007)

Some could be 3650RPM or 5000RPM. Actual blade speed can be changed with pulley size changes. Manufacturers determine the best efficiency considering the motor used.


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## jlhaslip (Jan 16, 2010)

Doesn't much matter what the motor rpm is, or the blade rpm... keep your fingers out of the way...


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## rrich (Jun 24, 2009)

Induction motors (Single Phase) typically run at about 3450 or 1725 RPM. These numbers are approximate as there is something called "Slippage". (The lower RPM is due to the motor design having half the electrical poles of the higher RPM motor.)

The way to think of the motor RPM is cycles per second times 60 seconds per minute less the slippage factor. 

A typical induction motor on North American electrical power runs at 3600 RPM less the slippage factor. The same motor being used in Europe will run at 3000 RPM less slippage.

Most manufacturers make a common frequency motor designed to run on 50 Hz or 60 Hz electrical current. The machine manufacturer determines the appropriate final RPM speed for the cutting tool. (Saw blade, shaper, jointer head, etc.) This speed is adjusted by the use of pulley diameters for the belt drive system. One should assume that machines intended for 50 Hz electrical markets would have different pulley diameters than those intended for 60 Hz electrical markets.

It is possible to alter the RPM speed of the cutting tool by changing pulley diameters. To do so would be unwise as the pulley diameter changes would negate both the machine manufacturer's engineering for the machine as well as the cutting tool manufacturer's engineering for the cutting tool itself.

*We interrupt this post to bring you breaking news.* 

The stated RPM of the motor is not an exact number. 

The stated RPM is close to the real number, however the distributed electrical power may deviate from the nominal which causes the motor RPM to vary. 

The actual motor RPM is affected by phase slippage in the design of the motor. The slippage factor is typically 2% to 3% HOWEVER may be as high as 7%. (7% x 3600 = 252 or a nominal RPM 3348.)

*We now return to your regularly scheduled post.*

For the obsessive among us, the only way to know for sure is to measure your motor RPM. (Probably could be done with a precision strobe light and a bit of white paint on the motor pulley.) I am uncertain as to what I would do with the information if I had the actual number.

e.g. I have no idea what the motor RPM or blade RPM are on my Unsay. All I know is that the saw cuts rather well and I haven't been able to stall the blade. I'm happy.

Even more . . .
Your variable speed router has 4 or 5 speed settings, Fast, Faster, More Faster, Very Fast and Extremely Fast. Extremely Fast is said to be 22,000 RPM on my PC 7518 and Fast is said to be 12,000(?) RPM. All that I know is that panel raising bits cut better at the Fast setting and round over bits work best at the Very Fast or Extremely Fast setting.


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## papazian (Mar 27, 2010)

*Thanks for your thoughts on motor rpm!*

Thanks for pointing out that the motor rpm can be different than the blade rpm due to different pulley diameters. I was surprised when I saw the different motor rpm ratings and didn't know what to make of it. It doesn't seem important now. Thanks for clearing that up for me. One less thing to think about. I guess the main issues form me go back to price, fence quality and maybe riving knifes. Thanks again. 
I'll probably look for a good used saw if I can find one. If not the Grizzly's look nice for the money.

:smile:


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## rrich (Jun 24, 2009)

If you are buying a new table saw, decide upon the fence system first. After the fence, you won't discover very much difference between saw brands 20 years from today. As long as you treat the saws well and maintain them correctly, in 20 years there will be little difference between brands.


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