Restore 1953 unisaw or put motor mount on new Shopfox W1837

[Reggie Burnett]

There is a shopfox avilable up here new but with a broken motor mount. They want $500 for the shopfox and I already own the unisaw. The unisaw is 1HP.

Opinions on which way to go? I'm literally on the phone with woodstock right now trying to find out how much it will cost to get a new motor mount.

Thanks!

[Ryan Lloyd]

Do you have the time and knowledge to restore the Unisaw? It can be a lot of fiddly work to bring an older, potentially neglected, tool back into shape. If you are up for it, I would go with the Unisaw for the better rails and fence alone. Used table saw motors are readily available, if you require more power.

Once restored, the Unisaw will maintain resale value. You will be hard-pressed to get that $500 back out of that ShopFox saw.

The only thing that would tip me towards the ShopFox is if going that way will get you up and running immediately, versus a long delay in making the Unisaw operational.

Good luck.

Regards,
Ryan

[Reggie Burnett]

I have the time and though I have never restored one I'm pretty hands on and I think it can't be that hard. I've had it awhile and already restored the table to a nice finish and have already put a shopfox fence on it some years ago. So at this point I was just going to pull the guts out of the unisaw and clean everything up, paint the cabinet, and likely replace the bearings on the arbor. I also plan to rewire the bullet motor to 220v

I was leaning on staying with the unisaw mainly because I already have it and I like the castings and trunnion assembly better than the hybrid saws. The only negs on the unisaw are right leaning blade and no riving knife.

[Bill Dufour]

New bearing are around $30 for both. If the arbor threads are good it can be reused forever. If worst comes to worst a new arbor with two new bearings is a little over $100.
Remove the top,four bolts, wash out the moving surfaces with penetrating oil mix and apply triflow, that is it for the rebuild. Maybe a new belt.
take your time to align top carefully after relube to reduce kickback and keep accuracy.
Bill D.

[Mike Cutler]

You already have the UniSaw. I say put some elbow grease into the one you have.

[Mike Henderson]

A 1 HP cabinet saw is underpowered. I'd definitely look for a bigger HP motor if you're going to restore the Unisaw. I expect that back when that Unisaw was made, higher HP motors were expensive and perhaps that's why they only put a one HP motor on it. I expect most people would recommend 3 HP as the minimum for a cabinet saw today.

Mike

[Matt Day]

A 1hp motor will be fine for a large majority of work if you’re doing general furniture and plywood cutting. If you want to rip 12/4 oak all day, yeah, 1hp is underpowered.

For thicker stock, you’ll just need to slow your feed rate.

If you want to fix it up as a “user” saw and not paint, you can leave the guts in and do a good cleaning of the gears with the top off.

Bullet motors will need more maintenance than a couple bearings like most motors would. Check the OWWM Wiki for a good tutorial.

[Mike O'Keefe]

I've had a 50's vintage Unisaw for 20 year's now. I've never had a problem with the saw being underpowered. I've cut 2" ash-white oak never had a issue. I would stick with the Unisaw. Mike O'Keefe

[David Kumm]

If the uni motor is original it will be a repulsion induction motor. I've never used one but they tended to be large with lots of copper and ran cool, had lots of torque for their size, and low start up amps. If in good condition, they are preferred by the old iron guys as they outperform relative to their hp ratings. I'm not advocating, just sending you to do some reading. Dave

[Mike Henderson]

If the uni motor is original it will be a repulsion induction motor. I've never used one but they tended to be large with lots of copper and ran cool, had lots of torque for their size, and low start up amps. If in good condition, they are preferred by the old iron guys as they outperform relative to their hp ratings. I'm not advocating, just sending you to do some reading. Dave

A repulsion induction motor is just an induction motor once it is up to speed. And all motors of the same HP and RPM have the same torque. The definition of HP is torque times RPM times a constant.

You can certainly cut wood with a 1 HP saw, but it's a lot easier and quicker with a 3 HP saw. If you stick with the 1 HP motor, use a thin kerf blade.

Mike

[Bruce Wrenn]

Hundreds of thousands of these bullet motors have labored faithfully in woodworking shops since 1937. Most of their lives was spent spinning steel blades, which dulled quickly as compared to carbide blades. This meant they were under a greater load most of their working years, yet they faithfully chugged right along. I wouldn't dismiss the bullet motor just because it is only rated 1.0 HP. When I taught shop, we had a 1.0 HP bullet motor Uni, and a 3.0 HP induction motor Uni. "When the rubber met the road," there was no difference in performance between the two. Most of my students chose the bullet motor saw as it had the better fence system ( Biesemeyer clone) on it.

[David Kumm]

Mike and Bruce, I understand that in theory there should be no difference between two motors of the same rating, new or old. In practice, my old large frame cast iron motors seem to outperform their ratings- at least when woodworking. Makes no sense but my old machines had lower hp motors than my new ones yet don't bog down or burn up as I would have expected. I can't speak to the uni motor but I've replaced or rewound more motors less than 20 years old than motors over 40 years old. A new Chinese motor of 3 hp may have more power but probably also a shorter life. Don't get me started on most Euro motors in woodworking machines. I don't like them much either. Dave

[Mike Kees]

Reggie ,keep the Unisaw. I have experience with at least three of them now that I have owned. One of my employees bought one with a 1.5h.p. motor and it works fine.

[David Buchhauser]

I think that perhaps some of the older motors were "under rated" as far as the stated HP, and some of the newer motor ratings are for 'Peak HP", not continuous. I'm sure that this varies from manufacturer to manufacturer. Just my opinion.

[Pete Staehling]

I'd keep the unisaw. Depending on what "restore" includes I might or might not bother with some or even all of what you plan. Personally, I'd only do the stuff required to put it in good working order. Paint and polish I'd skip. Just me though. If that stuff floats your boat have at it.

[Mike Henderson]

I think that perhaps some of the older motors were "under rated" as far as the stated HP, and some of the newer motor ratings are for 'Peak HP", not continuous. I'm sure that this varies from manufacturer to manufacturer. Just my opinion.

I highly doubt this. Making a motor that was "under rated" would cost more than making a motor that was accurately rated and there was competition "back in the day" just like there is today.

And new induction motors are not rated at "Peak HP" (whatever that is), they are rated for continuous power output at the specified HP. The big difference between modern motors of the same HP rating is in the efficiency.

Mike

[Mike Henderson]

I have a theory about why some people think that those older repulsion-induction motors were more powerful than they are. I have to start with a short discussion of how induction motors work.

First, induction motors are rated with temperature as one of the limitations. A 1 HP motor can be operated continuously at 1 HP and will not exceed a specified temperature if operated within the ambient limits. You can operate that 1 HP motor a bit beyond 1 HP but it will draw excessive current (beyond nameplate) and will eventually overheat and fail.

The rated RPM of a motor is the RPM at the rated HP. A 60 Hz two pole induction motor will normally be rated at 3450 RPM. When it's not loaded it will run at close to 3600 RPM. If you overload it, it will operate at less than 3450 RPM.

A standard capacitor start induction motor, when used for something like a table saw, will start to slow down as you push the work into the blade. If you have a low powered motor, you can fairly easily push too fast and bog down the motor. In other words, what you're trying to do will require more HP than the motor has. This will slow down the RPM and as you slow down the RPM, you reduce the HP of the motor since HP is directly related to torque and RPM. The more the motor slows, the lower the HP and fairly quickly the motor stalls. Anyone who has used a low HP motor on a table saw will be familiar with this.

Now, let me discuss the repulsion-induction (RI) motor. The RI motor has a starting technique which produces a high torque. This method is useful if you have a load with a lot of inertia - it provides a way of getting that load up to speed where the induction portion of the motor can drive it.

So why put an RI motor on a table saw, which starts with essentially no load?

Let's look at a low HP RI motor in the situation described above. As you push the work into the blade and overload the induction portion of the RI motor, the motor will start to stall, just as described above. But when the motor slows to about 2500 RPM the starting circuit cuts back in and provides sufficient additional torque (and, of course, HP) to prevent the motor from stalling. The operator will generally notice the slower speed (must be BELOW 2500 RPM) and slows down the feed rate, allowing the motor to recover to 3450 RPM. This recovery causes the starting function to be disconnected and you're back to normal induction motor operation.

So, can you do more work with a 1 HP RI motor than a 1 HP capacitor start induction motor? No, unless you're willing to operate the motor at under 2500 RPM continuously where you're gaining extra torque and HP. And if you tried to do that, you'd burn the motor out because it's drawing excessive current.

But what it does do is keep the motor from completely stalling and gives a better experience to the operator. The operator does not have the blade stall in the work and have to figure out how to recover from that. They just have to back off their pushing and they can keep working.

So back to my question - why did they put RI motors on a table saw? I believe it was because they recognized that the motor was under powered but the RI motor would improve the operator experience.

So why don't they use RI motors on modern table saws? RI motors are more expensive than standard capacitor start induction motor and they use brushes which are a maintenance issue. And since they were used only to improve the operator experience with a low HP motor, you don't need them if you have a motor of sufficient HP.

A 3 HP motor (for example) would not be overloaded enough times to take advantage of the repulsion start function.

So one more question - if the RI starting circuit can provide all that extra torque, why take it out of the circuit at a certain RPM? Why not just leave it in and get a two (or more) HP motor out of the combination? The answer is heat. To get that extra HP, you have to put more current into the motor (at rated voltage) and that generates excessive heat which will eventually destroy the motor. There's no free lunch.

Mike

[Earl McLain]

Great info Mike--i appreciate it.
earl

[Charles Lent]

If the uni motor is original it will be a repulsion induction motor. I've never used one but they tended to be large with lots of copper and ran cool, had lots of torque for their size, and low start up amps. If in good condition, they are preferred by the old iron guys as they outperform relative to their hp ratings. I'm not advocating, just sending you to do some reading. Dave

I agree with David. That motor will perform better than the 2 hp induction motors of today. Keep it, and restore that Unisaw. Your children will inherit it.

If you pull the top off, keep track of the locations of the spacer shim/washers between the cabinet and the top and put them back in their original positions. It will make getting the top back on and flat much easier. New bearings in the arbor and motor, and new belts will likely be all of the new parts that you will need. Cleaning, lubricating, and maybe paint are the rest of the job and mostly labor. I cleaned up a 1983 Unisaw in 1998, and my saw search is over. I couldn't want a better saw, and my son will inherit mine.

Charley

[Reggie Burnett]

Thanks guys for all the info and discussion. I'm going to keep the unisaw and try to do a full restore (or at least clean up the inside and paint the cabinet back to stock Delta gray). I like the idea of really cleaning it up. I don't think the power of the motor really bothers me. If it does I'll look into a more powerful motor.

[Mike Henderson]

I agree with David. That motor will perform better than the 2 hp induction motors of today.

Charley

I'm afraid that's not a true statement. Please see my explanations about this earlier in the thread. A 1HP RI motor will provide the same HP as a modern 1HP induction motor. There's an easy way to verify this and that's to look at the input voltage and current. There's no free lunch - to generate 2HP you have to put a certain amount of electrical energy into the motor.

A HP is a bit less than 750 watts (745.7) - I'll use 750 as a round number. But a small motor, such as a 1HP, is only 70 to 75% efficient. Let's use 75% to be generous. That means you have to put in 1000 VA (volts times amps) to produce 1 HP. At 120 volts in, that means about 8.3 amps in. At 240 volts, it would be 4.15 amps in. For 2 HP, double those numbers - at 120 volts, you'd need about 16.6 amps and at 240 volts you'd need 8.3 amps.

If the motor is less than 75% efficient you'd need more amps. At 70% and 120 volts you'd need about 9 amps for 1HP.

You can't get more out of a motor than you put in.

Finally, if these motors were so wonderful - more powerful than a modern induction motor rated at twice (or even three times!) the RI motor's HP - manufacturers would still be installing RI motors in modern cabinet saws. But we haven't seen any RI motors in modern cabinet saws for many, many years.

Or, we'd have commercial shops buying up all the old cabinet saws with RI motors so that they'd get more power for less electricity usage. But we don't see that either. Most commercial shops will have cabinet saws with 5 HP induction motors.

Mike

[Larry Edgerton]

I just gave a friend a 1hp Unisaw, and it cut a lot better then the Hp rating would lead you to believe. When it was in my shop it performed better than a PM66 I had with a 3hp. Only reason I let it go was I moved and had four saws, two had to go. I would not even consider a hybrid over a Uni/PM. I hate gray, so the one I gave away had a flame paint job, just a thought..........

[Chris Hachet]

I have the time and though I have never restored one I'm pretty hands on and I think it can't be that hard. I've had it awhile and already restored the table to a nice finish and have already put a shopfox fence on it some years ago. So at this point I was just going to pull the guts out of the unisaw and clean everything up, paint the cabinet, and likely replace the bearings on the arbor. I also plan to rewire the bullet motor to 220v

I was leaning on staying with the unisaw mainly because I already have it and I like the castings and trunnion assembly better than the hybrid saws. The only negs on the unisaw are right leaning blade and no riving knife.

I would suggest a shark guard for the uni or something similar. Unisaws are pretty simple machines, and the knowledge base on them is pretty high.

[Chris Hachet]

Reggie ,keep the Unisaw. I have experience with at least three of them now that I have owned. One of my employees bought one with a 1.5h.p. motor and it works fine.

Pretty much this.