Hot rod table saw

[Tony Jester]

Hi, The motor on my old Craftsman 10" table saw finally burned up a few months ago. My wife and I are building a house and I am constantly needing to rip long lenghts of 2-by material. I'm sure a new blade would have helped, but the saw would always overheat badly and want to stall. I always wanted a new motor, so even though I'm completely broke because of the house, I was almost happy when the old one gave up.

I thought about Harbor Freight, but the ones I used on my air compressor just didn't last. I ended up buying a 230v 3 hp (14amp) Marathon brand air compressor motor from Enco for $162, part number 891-4959. I was surprised by the quality, it seems like a very nice piece for the money. It is, however, very open and therefore needs some kind of a home-made sawdust shield. I wired in a dedicated 20 amp recepticle and bought 35 feet of #8 SJT with large twist-lock plug and used the original power switch.

As the new motor uses a 56H frame, it mounted right up with no problems. At the same time I got a new Freud rip blade. WOW! What a difference. That thing doesn't even slow down. It literally cuts like butter. When you start it, it INSTANTLY comes up to full rpm. It's REALLY amazing. Really worth the money. The long dedicated power cord is great also, something I should have done a long time ago. No more plugging and unplugging. That actually may be the best part.

Anyway, I thought I'd post because there are so many of these old saws out there and I am really, really happy with the results. Now, if I could only afford a good fence system...

-Tony-

[todd]

Good luck with that motor. A replacement motor would have had a a service factor of at least 1.0 and would have been totally enclosed, which would have kept out dust. I'd be really reluctant about putting a non-TEFC motor into a table saw. Hope it works out.

todd

[Denny]

Same thought Todd... I'm concerned about a dust fire with an open motor... Keep it clean, Tony... OTOH, I know how good it feels to have a saw and blade that just eats wood like it's a marshmellow puff...

denny

[Charley]

An open motor on a table saw is just looking for trouble, and using the original switch that was probably intended for 1 horsepower and 120 volts on the new 3 horse motor also spells disaster. The saw's wiring also needs to be upgraded as well as the power cord. If the switch doesn't short out and electrocute you it will surely burn up very soon, or it may weld itself in the ON position at the exact time that you really need to shut of the saw "right now" because of some saw cutting disaster. One of these stupid mistakes will likely burn down your new house that you have worked so hard to build, electrocute you, or saw your arm off because the saw won't shut off. If you still think you've made a great improvement in your saw, then I can only say that you had better have your insurance paid up.

[LRod]

I won't go quite the gloom-and-doom route of other posters, but I will point out some things that you may not be aware of:

A 3 hp motor is serious overkill for a contractor type saw. Due to the design of the motor mount, the only tension provided on the single belt is from the weight of the motor. Because of the single belt and only moderate tension available (and varies with the height of the blade) a lot of your 3 hp (probably half--maybe more) will never make it to the blade. A true 1½ hp (not a Sears 4 hp "developed") motor would have been plenty. When I replaced the motor on mine many years ago, I used a 1 hp and never found it inadequate.

#8 wire? Good grief. #12 would have been absolutely fine, although no one would have shaken their head at #10. But #8? Total waste of your money. Also, good luck getting that wire into anything rated at 20 amps.

If your testing was a rip, then your new rip blade would account for quite a bit of the difference in performance you noted.

The switch. A lot depends on what kind of switch was originally there. My old Craftsman had a simple toggle switch; sort of like the kind you'd find on a radio. It seemed fairly heavy duty, but it just looked like a toy compared to one of those cool green-on/red-off switches, which would be okay for your motor. If it was one of the more modern switches that Sears used on their saws, jointers, etc., it's probably okay (so long as it's a DPST). However, if the contacts were only rated at say 10 amps (not unlikely for the original 1½ hp motor), it's not beefy enough for the 3 hp current draw. You need to look at the ratings on the switch.

Marathon motors are considered decent, but with that open frame, don't look for a long life. That was a good price for a 3 hp Marathon, but not really the right motor for the saw.

[Leon]

Not likely, no sparks and most Craftsman machines were not equipped with TEFC motors. Nor was my Rockwell drill press.

[Tony Jester]

ENCO sells TEFC motors as well. Unfortunately for me, they are twice the price. I tried to make the point that, at the moment, I am seriously short on fundage. With the shield I mentioned, I think it will be fine.

[Tony Jester]

Wow, you have no spirit of adventure at all, do you. You expecting to live forever or something?

[Tony Jester]

The instructions that came with the motor were very specific about using #8 wire for anything over 25 feet as I recall.

Yes, I believe I made that point.

Yea, I realized after I posted I should have put a disclaimer in about the switch. All I need is a magnetic starter. Sometimes you can find used ones pretty cheap, especially 3-phase, which of course work fine for single phase also. If I ever find one, I promise to install it to make you guys feel better.

-Tony-

Shamelessly hotrodding everything he could get his hands on since WAY before that!

[Toller]

Don't post if you don't want advice. The person who owned my saw before me put a magnetic switch on that was too small for the motor. He "compensated" by using two poles rather than one, figuring the current was divided. Well, it fused closed. There are right way and wrong ways to do things; and you innovate at your own risk.

A new blade for $50 would have saved you from spending $160 on a new motor that is inappropriate for your saw. But go ahead doing things your way. Geez, I hope you are a troll.

[Greg O]

My Delta TS I bought new 5 years ago had an open motor. Delta's top-o-the-line contractors saw. I would not worry about it! Greg

[LRod]

Okay, then answer this for me: in your original post you said, "I wired in a dedicated 20 amp recepticle and bought 35 feet of #8 SJT with large twist-lock plug and used the original power switch."

I read that as the 20 amp receptacle was wired with 12 ga wire, true? If so, then you accomplish nothing by plugging 8 ga wire into that circuit. It's like coupling a 2" fire hose to a 3/4" garden hose. You're not going to get anything more out of that 2" hose than can be delivered through the intervening 3/4" hose.

What does the label on the motor say for FLA (full load amps)? Very likely 15-18. Even if it were the truest 3 hp motor on the planet, and operating under a constant heavy load (not possible with the contractor saw lashup) it might still run on a 20 amp circuit (12 ga wire) and would be absolutely comfortable on a 30 amp circuit (10 ga wire). Even 5 hp machinery is happy on a 30 amp circuit. This is what I'm getting at; 8 ga is way over the top. Toller must have written those instructions, that's how unrealistic it is.

I don't fault you for "following instructions", I'm just saying it was a waste of resources.

[Sailaway]

Charley wrote: An open motor on a table saw is just looking for trouble, SNIP

Ok, this I gotta disagree with - it smacks of the same argument that's been passed around a bunch of times about the DC's exploding from sucking dust.

My Craftsman TS has had the same open motor hanging off the back it came with 50 years ago, and it hasn't exploded or burned anyone's house down yet. Heck, it never even seems to get hot. I know that many older contractors saws came with open motors, and even some of the newer cheaper ones with the universal motors that are stuck up under the table have open housings. None of those are exploding or burning the owner's houses down.

While dust may be a hazard under certain circumstances, the speed at which that dust blows through this motor is at such high velocity and with so much air going in with it I just do not believe it is an issue.

BTW, this TS has been used all that time without any dust collection at all, unless you can count the old burlap bag hanging off the bottom - so yes the motor has been exposed to a large amount of dust over the years.

FWIW I am not advocating forgoing safety and common sense. Just that some things are straw men issues.

[Sailaway]

Charley wrote: >and using the original switch that was probably intended for 1 >horsepower and 120 volts on the new 3 horse motor also spells disaster.

Just wanted to add that I fully agree with this part - the OP is asking for disaster with this one. The original switch was a good one when it was made, but by today's standards it is not a high quality switch. In addition it is old and most likely worn, and I just cannot believe it is not seriously under-rated for the new 3hp motor.

[Mike Marlow]

[Mike Marlow]

Apparently your sense of humor is broken today Toller. Tony's comment is obviously a tongue in cheek comment.

Ummmm... didn't he state that the original motor bit the dust? That $50 blade won't do much once the magic smoke escapes.

[LRod]

I've been whoring myself since long before '99, too. It's just that it became easier to do when I got a webpage up. What I'm whoring, actually, is the Norm's Tools part of it, if you didn't know that already.

[Robert Bonomi]

I'm going to _disagree_ with your dissertation, but only 'somewhat'.

The "I2R" losses in the wiring between the breaker-panel and the motor are related to the _total_ resistance of the wiring between those two points. Using lower-resistance wiring for part of the run _does_ decrease the total parasitic loss.

With the start-up load being in the range of 2-3x the rated FLA, there is likely a measurable benefit to that 35 ft of 8 ga., vs an equal length of say 12 ga. -- *regardless* of what the rest of the wiring is (gauge _or_ length).

[Toller]

No, he said the motor overheated because of a lousy blade; but he wanted a new motor so he let it burn out. Then he bought a crap motor and a new blade.

[Mike Marlow]

A crap motor? Please Toller - don't do this to yourself.