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Forum topic by Dusty56 posted 03-24-2013 06:07 PM 932 views 0 times favorited 12 replies Add to Favorites Watch
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Dusty56

11660 posts in 2354 days


03-24-2013 06:07 PM

Topic tags/keywords: question unisaw table saw motors craigslist tablesaw

Hi , ” New 1.5H.P. 120v 1725rpm Equal to 3250rpm 3 H.P.” Quoted from a craigslist posting today for a Delta Unisaw.
1) Is this possible ?
2) why would we want a table saw blade to turn this slowly ?

http://westernmass.craigslist.org/tls/3699711051.html

thank you : )

-- I'm absolutely positive that I couldn't be more uncertain!


12 replies so far

View AndyM1949's profile

AndyM1949

14 posts in 556 days


#1 posted 03-24-2013 06:20 PM

Hmmm don’t sound right to me. my blade turns around 3600 rpm. If you put a slower motor on you saw (less rpm) with less hp. Its not going to preform as well. The motor speed and size of the pulleys on arbor and motor shaft determine the blade speed. hope this helps.
Andy

-- Andy, SC

View sprucegum's profile

sprucegum

323 posts in 664 days


#2 posted 03-24-2013 06:48 PM

1.5 hp is not the same as 3 hp pure and simple. Table saw motors are almost always 3250 rpm, 1725 is too slow unless you use unequal size pulleys to speed it up ( big motor pulley to small arbor pulley).

-- A tube of calk and a gallon of paint will make a carpenter what he ain't

View amagineer's profile

amagineer

1385 posts in 1263 days


#3 posted 03-24-2013 07:22 PM

I contacted the owner yesterday about the saw. He said his brother in law fried the original motor and replaced it with the 1-1/2 hp motor. I agree with the pulley ratio to up the rpm’s. A 4” pulley on the motor and 2.18 pulley on the blade arbor will give the increased rpm. I decided not to buy the table saw, looked like to much work to restore.
-don

-- Flaws are only in the eye of the artisan!

View JamesT's profile

JamesT

102 posts in 578 days


#4 posted 03-24-2013 07:44 PM

Rockwell/Delta Unisaw made arbor and motor pulley sets for both 1725 and 3450 RPM motors. The blade would turn the same speed with both set-up’s But of course they are not the same power, 1.5 HP uses approx 1119 watt of power, 3HP approx 2238. If someone installed a 1750 motor without the correct pully set, the blade speed would be one half what it should be.

-- Jim from Doniphan

View runswithscissors's profile

runswithscissors

967 posts in 691 days


#5 posted 03-24-2013 08:45 PM

Not only that, but a large motor pulley to a smaller arbor pulley yields less torque at the blade. Burt it was typical many years ago to use 1725 rpm motors that way. I’m guessing 3450 rpm motors weren’t that common or were too expensive.

View unbob's profile

unbob

419 posts in 569 days


#6 posted 03-24-2013 09:05 PM

The very old Unisaws used a repulsion induction motor, of 1725 and apparently 1425rpm. Those old motors had plenty of torque, and run very smooth, with a larger motor pulley. One problem is, newer motors do not fit correctly, and the right hand opening has to be cut larger, or one can not get full 45 blade tilt.

View Dusty56's profile

Dusty56

11660 posts in 2354 days


#7 posted 03-25-2013 01:02 AM

Thanks for all of the info / knowledge , Gentlemen.
I knew it didn’t seem to be correct , but I had to check with you pros anyway : )
Very interesting to read about the pulley size changes , and I believe those old beastly motors were called Bullet motors due to their shape.
The condition of the saw doesn’t make it very desirable for that kind of money in my book , Unisaw or not.
Thanks again : )

-- I'm absolutely positive that I couldn't be more uncertain!

View runswithscissors's profile

runswithscissors

967 posts in 691 days


#8 posted 03-25-2013 01:29 AM

Just looked at the photo for the first time. That is an “open, drip proof” motor, not good to use around sawdust, as on TS. Should be TEFC (totally enclosed fan cooled).

View Dusty56's profile

Dusty56

11660 posts in 2354 days


#9 posted 03-25-2013 01:45 AM

More good info . Thank you : )

-- I'm absolutely positive that I couldn't be more uncertain!

View David Dean's profile

David Dean

524 posts in 1565 days


#10 posted 03-25-2013 06:42 AM

Your not realy thanking about buying that are you I still have my grand father’s table saw and the same motor that came with it like he siad you take care of your tools they well take care of you. Let the owner sale it for srape.

View Dusty56's profile

Dusty56

11660 posts in 2354 days


#11 posted 03-25-2013 10:29 AM

No , I wasn’t wanting to buy it , I was just wondering about his statement regarding the HP being equivalent.
Another Craigslist Cukoo for Cocoa Puffs moment !! LOL

-- I'm absolutely positive that I couldn't be more uncertain!

View REO's profile

REO

615 posts in 740 days


#12 posted 03-25-2013 04:50 PM

in a word. No. it takes a given amount of force to remove a chip regardless of speed. In the case described here you will be able to make 1 1/2 HP worth of chips. this takes into account force, time and distance. You will only be able to do half as much. If you increase the speed with different pulley you will increase the speed but give away torque so you can only make a half sized chip. often the reason blades burn is not because they are dull but because they are not fed what they need to stay cool. When the proper feed rate is reached the chip takes the heat away and helps cool the blade as well. It really depends on whether you need to use 3 hp. Cutting 3/4 plywood you will be fine with 1 1/2 hp. Production runs of 6/4 oak and you will want the extra hp.

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