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Forum topic by mvh posted 08-13-2009 10:28 PM 1278 views 0 times favorited 9 replies Add to Favorites Watch
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18 posts in 2912 days

08-13-2009 10:28 PM

I am thinking of buying a different table saw as the old Ryobi BT3100 literally isn’t cutting it any more. I think it definately lacks in power amongst other things. Based upon the voltage and amps it seems to be about a 1.50 hp universal motor. I got this by taking volts (120) times amps (15) multiplied by a motor efficiency of about 60% then divide that by 746 watts, which is 1 hp. The saw is also rated at 4,800 rpm’s. It starts to labor while cutting 5/4 cherry.

I have read all the table saw reviews on this site and others several times over and people with contractor or hybrid saws with induction motor ratings of 1.50 to 2.0 hp seem to say that these saws have plenty of power. Most of these saws seems to have a rpm rating of about +/- 3,450.

My question is this- Since I have about a 1.50 hp saw now, would see a big difference in the ability to cut thicker stock if I were to obtain a saw with a 1.50-2.00 hp induction motor? I am guessing that I would some improvement, exactly how much I don’t know. My reasoning for thinkng this was is that slower blade speed equals more torque to the blade. But I am not sure. Just trying to find out if 1.50 to 2.00 hp motors will be enough for my needs.

Since I like old stuff, the ideal saw would be an old unisaw from the 50,60, or 70’s and fix it up, but unfortunately 3 hp cabinet saws of any age don’t show up in the online or paper classifieds very often. And I can’t go buy a new Griz 1023 since my wife already complains about the hobby. I am trying to broaden my chances of obtaining a used quality saw that will last many years and meet my weekend project needs- mission type household furniture, etc.

Any information would be greatly be greatly appreciated.

9 replies so far

View Mike57's profile


61 posts in 3327 days

#1 posted 08-13-2009 10:50 PM

Not sure where you’re located, but if you’re in Michigan there is a used wood equipment store in Holly (“Holly Wood Equipment”). I picked up a 3hp 220V unisaw and a 15” planer for a pretty good price – and they delivered and setup the machines.

You might also try Craig’s list or a local woodworkers store for someone local who might be looking to sell what you need.

View mvh's profile


18 posts in 2912 days

#2 posted 08-13-2009 10:54 PM

Utah- I check craigslist, but our local news has a classifieds that is pretty extensive.

View knotscott's profile


7147 posts in 2800 days

#3 posted 08-13-2009 11:18 PM

mvh – I had a BT3000 in the shop for a while…it’s a nice little saw with some limitations. I’ve read many posts from people who’ve made the jump from a BT to a full size contractor saw or hybrid, and most seem pretty impressed with the perceived power difference, and feel of the additional mass. Induction motors in general tend to have a bit more torque than universal motors. You’ll also be gaining considerable table space, and mass. Even though the BT is capable of cutting to full blade height, it’s slower and labors more than most contractor saws or hybrids. Keep in mind though, that blade selection and alignment are significant factors in the final performance of any saw.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

View RedShirt013's profile


219 posts in 3086 days

#4 posted 08-14-2009 12:05 AM

Maybe trying a new good quality blade would give you the result you are looking for on your current saw. New saw or old saw you will need to buy a nice TS blade anyway.

-- Ed

View Beginningwoodworker's profile


13347 posts in 3097 days

#5 posted 08-14-2009 12:52 AM

I have a older model Unisaw that I restore check out my blog, I painted it added a 1-1/2 hp motor and it works fine.

View EEngineer's profile


1055 posts in 3038 days

#6 posted 08-14-2009 04:30 AM

First of all, universal motors are less efficient overall than induction motors. For the same specs you quoted for your universal motor, an induction motor will deliver ~2HP (60% vs 80% efficiency).

Second, universal motors tend to operate differently under load than induction motors under load. Specifically, the efficiency falls off faster under increasing load with a universal motor than with an induction motor. Efficiency vs load curve with an induction motor is “flatter” than the curve for a universal motor. End result: an induction motor is better for power tools than a universal motor when heavily loaded.

As for old tools: as copper and iron costs increased, the amount of copper and iron they put into newer motor designs decreased. An older induction motor is most likely more powerful, under load, than a newer induction motor and will most likely survive longer under heavy load conditions.

So, yes, buy an older tool and recondition it. You’ll be happy. I am on record here on Lumberjocks many times recommending this. I run a 60’s era saw with a 1HP motor and haven’t found any reason to upgrade it yet (but I haven’t sawn 5/4 cherry, just 3/4 cherry and oak so far).

-- "Find out what you cannot do and then go do it!"

View mvh's profile


18 posts in 2912 days

#7 posted 08-14-2009 06:11 AM

Thanks EE, what you said about the load curve makes a lot of sense. From the sounds of it, a 2 hp would fit my garage shop needs since I’m not into production.

View EEngineer's profile


1055 posts in 3038 days

#8 posted 08-14-2009 01:30 PM

Hmmm, maybe I wasn’t clear. My point was that maybe a 1.5 HP induction motor would be sufficient given the difference in motor characteristics. The same circuit you have now (provided you can meet the startup surge – both kinds of motor take more current during startup) would support up to a 2HP induction motor. If you can find a 2HP induction motor, by all means go for it but 1.5 HP seems more common on table saws – I am not sure if this is the case with older Unisaws.

There are many reasons not to like universal motors:
1. They take less copper and iron than induction motors which is why manufacturers like them; they cost less to build. For hand tools, the reduction in weight is an obvious advantage. But the reduction in thermal mass makes them easier to burn up. In general universal motors are used for intermittent duty; continuous duty applications will have an induction motor.
2. They tend to produce less torque. That’s why they are designed to run faster. mechanical HP = torque X RPM, so with less torque, you need higher RPM to get the same HP.
3. Brushes are a pain – in fact, most of the differences I described between universal motors and induction motors are due to losses in the commutation process. As brushes wear out, losses increase. That brings up an interesting point: if you have many hours on your old saw, you might be able to get some more life out of it by replacing the brushes.

-- "Find out what you cannot do and then go do it!"

View mvh's profile


18 posts in 2912 days

#9 posted 08-14-2009 06:41 PM

Thanks EE, you were very clear EE. The start up surge is not a big deal as I have a 20 A 240 V line to the garage already. The only reason I said 2 hp is that there is a used Delta 10” Tilting Arbor Saw with one in the classifieds. It is not a unisaw, but looks like an older hybrid model or something. Not having much luck finding info on the internet that matches the classified picture. It has the old jet lock fence, cast iron table, but stamped wings. I am trying to find out more info such as model number and stuff from the owner, but have not heard anything yet. It is posted for $220, but depending on the information supplied I think $220 might be a touch much since it looks like it needs a little work.

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