Running motors at 40-80% power OK or risk of damage?

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Forum topic by Thuzmund posted 12-10-2013 05:14 PM 1080 views 0 times favorited 7 replies Add to Favorites Watch
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148 posts in 1625 days

12-10-2013 05:14 PM

Topic tags/keywords: question

Hi everyone,

I will say something that amazes you, then say something that will probably make you scratch your head, then ask a question.

- I do a lot of woodworking in a basement apartment in the middle of a 5-apt unit. My two neighbors both work during the day and don’t mind the noise at night. I make them things and it’s a good fit. I am the luckiest idiot around! But I would never take this kindness for granted, so…

- I had an idea to use variable speed controls (like those used with routers) to run my noisy table saw at 75% power. It’s much quieter, and actually the quality of the cut is good! Seems like a win-win: I can work a bit later at night and my basement doesn’t sound like a jet engine laboratory.

- The only drawback would be if this practice risks damage over time. I don’t know much about electronics so I thought is best to ask. I run 15A Craftsman table saw most often. What do you guys think?

PS, assuming that this is not a foolish practice, i suggest others give this setup a try. You have to play with the setting because each motor has a diffierent minimum level of power. TS: 75-80% power, BS/Miter Saw/Sander: 40-65%, etc. Play around with it. I mean, isn’t less noise a big selling point on some high-end tools?

Looking forward to reading everyone’s insight.

-- Here to learn

7 replies so far

View Dallas's profile


3599 posts in 2483 days

#1 posted 12-10-2013 05:23 PM

If your Craftsman has a universal motor, you could conceivably do this, although I would think heat build up would be significant and the brushes would wear more quickly.
If it has an induction motor, (with capacitors), NO!
You will kill the motor.

the less noise feature of the larger, ie: cabinet saws is that they are better balanced, have heavier motors and a lot less vibration.

-- Improvise.... Adapt...... Overcome!

View Fred Hargis's profile

Fred Hargis

4984 posts in 2490 days

#2 posted 12-10-2013 05:28 PM

If that table saw has an induction motor (bump(s) on it) that speed controller won’t work. About the only way you can vary an induction motor’s speed is with a VFD (variable frequency drive). You might have a saw with a universal motor ( a screamer, with brushes) and the speed control would slow that down. If it (the controller) doesn’t burn out, the motor will suffer some damage. There are motor made for having their speed controlled, look at any expensive lathe. It will probably have a 3 phase motor with a VFD. I’d suggest you give up on your plan. You could move to doing hand tool work late at night.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Loren's profile (online now)


10382 posts in 3644 days

#3 posted 12-10-2013 05:53 PM

I have one of those router speed controls and I tried using it on a
15 amp circular saw. It blew the fuse in the speed controller
the first time. There was too much start up load.

View bigblockyeti's profile


5112 posts in 1717 days

#4 posted 12-10-2013 06:16 PM

Bad idea, it only make sense with smaller routers as you can get the bit speed down to where it’s safer to use. Those who designed your saw knew what they were doing when determining what the blade and motor speed should be. While universal motors can be connected to a variable speed controller, the motors on tablesaws are usually close to the same size as the very largest routers, also needing much more start up current due to a moment of inertia much higher than even a big panel raising bit. Motors not specifically designed for this will lead a shorter life due to the reduced airflow cooling the field and armature, combined with the greater heat generated by using more current. It won’t work with an induction motor at all.

View exelectrician's profile


2327 posts in 2424 days

#5 posted 12-10-2013 06:24 PM

Try doing what I do – Install a 7 1/4” ultra thin kerf DeWalt blade on your 10” saw,

The results are truly amazing!

-- Love thy neighbour as thyself

View Thuzmund's profile


148 posts in 1625 days

#6 posted 12-10-2013 06:33 PM

Thanks for all the sagacious advice! See, that’s why it’s good to be an idiot in public, instead of keeping it all to yourself! :-D Looks like I better halt this idea ASAP

-- Here to learn

View Loren's profile (online now)


10382 posts in 3644 days

#7 posted 12-10-2013 06:42 PM

A table saw with a belt drive induction motor is very quiet
with no blade on it. Most of the noise comes from air
turbulence, so running a small blade makes for quieter
cutting. I have a couple of table saws with belt drive
and smaller blades and they are not too loud, though
I still wear hearing protection.

Early table saws ran on foot power or jackshafts powered
by water wheels. They ran a lot slower.

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