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post #1 of 18 (permalink) Old 11-30-2014, 03:26 PM Thread Starter
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I have an old craftsman 10inch table saw.The motor is starting to show it's age I was thinking maybe a new motor but not sure what to get the old one is 11/2 hp and 3200rpm should i get more HP or more RPM or both.Thanks in advance ernie
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post #2 of 18 (permalink) Old 11-30-2014, 03:37 PM
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I would def match the rpm,as far as hp,thinking your machine is single belt so why go any mor hp unless you find a deal
My 2 cents
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post #3 of 18 (permalink) Old 11-30-2014, 03:58 PM
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The only thing I could think of is wiring the next motor for 240 if it's capable . The extra torque is always nice . I sure noticed a difference with my cabinet saw as it is tough to stop the blade now.

I donít always insulate , but when I do .
Ok ,I never insulate

Last edited by RainMan 2.0; 11-30-2014 at 04:53 PM.
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post #4 of 18 (permalink) Old 11-30-2014, 04:05 PM
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A 3200 rpm motor is an oddball. Stock off the shelf rpm is 3450. The extra rpm won't make a difference so to speak. Your biggest issue may be finding a motor that is the same mount. The existing is supposed to have the mount code on the spec plate. You might find one with more hp and the same mount but if it is larger diameter it might affect the tilt or how much the blade extends above the table.

The option is to have yours refreshed with new bearings and any other wear parts. That might be more cost effective and a rebuilt electric motor can be just as reliable as a new one.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
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post #5 of 18 (permalink) Old 11-30-2014, 04:09 PM
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Excellent points and advice,Chuck
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post #6 of 18 (permalink) Old 11-30-2014, 10:47 PM
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Thanks Al.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
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post #7 of 18 (permalink) Old 12-01-2014, 07:02 AM
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Quote:
Originally Posted by RainMan1 View Post
The only thing I could think of is wiring the next motor for 240 if it's capable . The extra torque is always nice . I sure noticed a difference with my cabinet saw as it is tough to stop the blade now.
Once agaaaain, you have the same two windings... each have 120VAC across them, each winding has the same amperage flowing through it, whether wired for 120VAC or 240 VAC. Only time you should notice any difference would be if you have inadequate or borderline wiring. The 240VAC does pull less line current(half that at 120). The wattage is the same. The motor doesn't know or care which voltage it is running from... all looks the same to it!

Yet this tired old myth persists. 1.5HP is 1.5HP! Got a 240VAC outlet to plug it into? Sure, wire it 240VAC! Otherwise it will work just fine on 120VAC.

Also there is a safety issue if the power switch is single pole. The motor would be hot all the time on 240VAC, whether running or not! If your switch is double pole and breaks both sides of the line... you should be ok rewiring for 240VAC. Otherwise you would have to change the switch as well!

And speaking of safety, I don't even want to know how(or why for that matter) you are trying to stop the blade.

Many of the newer saws are running 1.75HP or 2HP. Most of these have a serpentine belt capable of delivering that extra HP. The single v-belt is more apt to slip under the larger load. Won't notice a difference unless you are really pushing it hard, though.

I would not recommend more than 2HP in any case... remember the rest of the saw is not designed for it! 1.5HP at 3450RPM(Chuck's correct... 3200 is an oddball) should do anything that saw was designed to do!

I have found that hand tools are the best choice when I want to make mistakes at a slower rate of speed.

I don't suffer from insanity. I enjoy every minute of it.

Last edited by Dmeadows; 12-01-2014 at 07:25 AM.
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post #8 of 18 (permalink) Old 12-01-2014, 11:15 AM
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Go to the nearest High School, and see if they have a Class that re-motors. I took the course in my High School; it was called Electrical Trades.
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post #9 of 18 (permalink) Old 12-03-2014, 04:11 PM
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As an Electrical engineer I agree with everything that Duane stated about dual voltage single phase motors. I especially appreciated the safety comment about using a double pole switch for 240 volt motors. In the USA, 240 VAC is supplied with two lines while 120 VAC is supplied with one line and ground. While a single pole switch will turn the 240 VAC motor on or off, it will only switch on/off one of the two lines. This will leave the other line directly connected to the motor and the motor will have voltage applied to it even if the switch is off. UL will not allow any manufacturer of a product that uses a 240 VAC motor that is built into the product to use a single pole switch to turn off the motor.

On capacitor start single phase motors, there is a start winding that has a capacitor in series with the winding. The purpose of the capacitor is to provide a phase shift on the start winding. This will help the motor start by providing extra starting torque due to the phase shift. These motors also include a centrifugal switch that is internal to the motor that will open its contact and will remove this capacitor and start winding from the motor circuit once the motor has reached an adequate speed. If this switch goes bad and stays switched on, the motor will quickly overheat and will likely also burn up the start capacitor. If the capacitor is open or the centrifugal switch doesn't engage, the motor will not start and will also quickly overheat.

Some manufactures of products will incorporate dual voltage/dual frequency motors into their design. Typically these are 120/240 VAC, 50/60 Hz, 2875/3450 RPM. These motors have been specifically designed to run on either 50 or 60 Hz without burning up. This is a compromise. The motor actually will only run at optimum efficiency at one frequency. In the case of a dual frequency motor, the motor manufacturer will design the motor to be optimum at 55 Hz, but will run sufficiently efficient at either 50 Hz or 60 Hz to not overheat. The reason that the product manufacturer has included a multi-frequency product is so that it can be used around the world, without having to have different stocked items for different voltage products. A similar thing is often done on voltages. Some motors are listed as 208/240 VAC, 50/60 Hz, 2875/3450 RPM. Again this is a compromise. A motor can only be efficient at one voltage point for the winding. If the motor has a voltage range instead of a fixed voltage, it just isn't as efficient as it could be. In this case, the motor will have a maximum efficiency at 224 VAC and 55 Hz. But it will run cool enough to work well at both voltages and at both frequencies. The reason I am telling you about this is that while these types of motors help the manufacturer of a product reduce the number of SKU's (stocking units) that he has to produce to sell products around the world, it is costing you in inefficiency. These motors will draw more current than fixed voltage/fixed frequency motors. Usually this is about 10 - 15% more power consumption. So don't go for these range of voltage/range of frequency motors if you can avoid them, unless of course you don't care about spending more money for power than you need to.

Glenn

Last edited by oldwoodenshoe; 12-03-2014 at 04:16 PM.
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post #10 of 18 (permalink) Old 12-03-2014, 06:15 PM
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My bad , your right Daune . I know ohms law off the top of my head so it only makes sense that a motor that allows for either type of wiring would still be drawing the same current in the end .
The reason I notice an improvement is my new cabinet saw is probably twice the HP of my of old contractors saw .
I can't remember exactly but I know the motor draws more than 20 amps , so the only way to run it is if it's wired for 240

I donít always insulate , but when I do .
Ok ,I never insulate
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