1953 delta unisaw help in deciding if its a good deal

[Mike Henderson]

This is a motor that can do 1 HP continuously; modern motors are branded with the max HP, which is what they generate just as they stall out. A modern "2 HP" is likely closer to 1 HP continuous duty. (Different vendors stretch the truth by different amounts, though).


Terry Therneau

I'm afraid that's not true. Induction motors are rated honestly and really can deliver the nameplate HP continuously. So, to take your example, a modern 2HP motor will deliver a constant 2HP if you load it to that level, say to operate a fan.

The reason your motor does not stall out is that when you start to load it down, and slow down the RPMs, the starting circuit cuts in and provides some additional torque. [Added note: The starting circuit cuts in at about 70% of rated RPM. So for a 3450 motor, you'll have to stall the motor to about 2400 RPM in order to get the centrifugal switch to cut in.] However, the motor was not designed to operate that way and if you loaded the motor to that level continuously, you would burn up the motor from excess heat (because you're drawing excess current - beyond the rated current for the motor). The reason you get away with it is that you pull back when the motor starts to stall out so you limit the amount of heat generated in the motor. Then you probably allow the motor to run with no load for a while which allows the fan to cool down the motor. But whatever you do, the important thing is that you don't operate it continuously at that reduced RPM and you allow the motor to cool down.

So, no, your 1HP motor only delivers 1HP in normal continuous operation. A modern 2HP induction motor will deliver a constant 2HP in continuous operation and not overheat.

As a side note, Repulsion/induction motors have brushes which eventually wear out. Plus they have more parts which makes them more expensive. That's the real reason all the manufacturers moved away from repulsion/induction motors. Additionally, Repulsion/induction motors have high starting torque and that's generally not needed in woodworking tools because we start them unloaded.

The standard induction motor is much better suited to woodworking tools.

Mike

[A modern induction motor will not stall out at it's rated HP - it will operate just fine. Note that some modern induction motors have a service factor. That's the amount you can exceed the rated HP and the motor will increase in temperature by 10 degrees C. However, operating at that heat level will degrade the life of the motor. So if the service factor is 1.1, and you have a 2HP motor, you can operate the motor at 2.2HP and it will get 10 degrees hotter - and it's life will be degraded.]

[You're probably thinking of universal motors which are rated at their "stall HP"]

[Cary Falk]

The Saw Center used too rebuild the arbor for $100 if yo don't want to tackle it yourself. I'm not sure if i would trust any machine shop. I did it and it is not hard but it takes some care and the part is getting harder to find.make you check the trunnion wherenit meets the cabinet. That is a weak spot.

[Matt Day]

I don't have a Unisaw but have restored a Powermatic 65, a Delta turret radial arm saw, and am working on a Northfield 12" jointer now. You will find soooo much information on rebuilding a Unisaw over on OWWM, you really need to do some research over there.

[Michael Dye]

I'm not sure where everybody stands as far as purchase price goes, but I'll pay $500 and up for an older Unisaw, any day. Ramon, your $150 saw is a steal. I know these values are subjective, but let's say you put $150 into the purchase, $50 into new arbor bearings, $400 into a bigger motor, and another $300 into a quality fence. Less than a grand for that saw, which will run circles around anything available today...........that's a steal even if you paid $600 for the saw. JMHO. For what it's worth, I buy and rebuild these saws all the time. Not just Delta/Rockwell, but Powermatic and the occasional Walker/Turner, as well. Whenever a potential buyer shows up, they are always amazed at the quality of the old saws. Haven't missed a sale in 30 years. Sadly, band saws are a completely different story.

[Charles Taylor]

Induction motors are rated honestly and really can deliver the nameplate HP continuously.

I think you're right that the PP is thinking of universal motors, whose HP ratings are pure fiction. There are some notable exceptions to the usual honest rating of induction motors, though, such as big-box store air compressors and, well, anything labeled Craftsman in the last 20 or 30 years.

[mark mcfarlane]

'What's a riving knife'.

A good friend of mine, an electrical engineer, was working in our community wood shop last weekend. He learned to operate a table saw by watching others in the shop. He was ripping a board on an old Unisaw without a riving knife and experienced his first kickback, which shot the board through the wall at the other end of the shop. Luckily he wasn't behind the cutoff. He had never even heard of kickback before this event.

Manuel, whatever you decide, do spend some time learning about how to use table saws safely before you turn one on and try to cut wood. Read a book on table saw safety. There are techniques to reduce the chance of kickback, including safety devices like riving knives, and there are ways to minimize the chance that you get seriously injured, like where you stand, jigs to hold the wood,... Kickback doesn't just throw wood, it can also be the cause of your hand to slip into the blade resulting in serious personal injury/amputation.

In 2003 there were 38,000 table saw accidents in the USA alone. http://tablesawaccidents.com.

I don't mean to sound too alarmist, but if you aren't familiar with what a riving knife is then I suspect you don't have very much woodworking experience, so the caution to do some safety study is appropriate. Table saws can be used safely, but you need to do your homework and then decide what's best for you.

[manuel ramon]

Just wanted to thank everyone for their input in restoration, motor,bearings, and most importantly safety .soon as i get her home ill start the pics .....i wanted to ask a question. Is there such a thing as bearings for the blade

[Chris Fournier]

Sounds like a good deal. Looking at the insert it seems that the saw came with a blade guard, sorry I'm too lazy to look up parts diagrams. If this is so there is a mounting point for the blade guard. Make your own kerf splitter and you have a very safe saw. Don't get hung up on "riving knife", a kerf splitter will do. I made mine out of hard maple and it served me well for over 10 years!

[ken carroll]

Manuel,

The 1hp bullet is a fine motor. I have a 1952 unisaw - just like yours and would not hesitate to use it to rip 2" hardwood even though I have a 1946 5hp Oliver alongside it. A sharp thin kerf carbide blade is required for best performance, and yes, $150 is a great price.

You will not kill yourself because you don't have a riving knife but advice to learn how to use a table saw properly is good advice. I have no riving knife or splitter on my Uni and I am still around.

One final thing I don't agree with the advice to automatically replace the arbor bearings. I guess I always get in arguments about this on OWWM. The bearings sound and feel will tell you if they need replacing. Would you automatically replace the wheel bearings on a used car?

[John TenEyck]

No, only the arbor bearings.

John

[Matt Day]

The hole in the blade goes over a threaded "bolt" and tightened up with a nut. That "bolt" is called the arbor and the nut is an arbor nut. The arbor spins on bearings which usually need replacing on a saw of this age (assuming they haven't been replaced before).

[Mike Goetzke]

I put a SharkGuard splitter/blade guard/dust collection on my 1950 Uni. Watch out it's addictive- I only planned to clean mine up a bit and use it and ended up completely restoring it including the motor.

Mike

[manuel ramon]

Ken,ill make sure i take my time and not rush in and start replacing everything at once which i normally do with other things.then go to find out it wasnt even needed .i guess if it aint broken why fix it .im probably just excited bout getti g the unisaw.