Need help with old Craftsman radial arm saw electrics

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Old 06-18-14, 04:52 PM
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Need help with old Craftsman radial arm saw electrics

Hi folks,

I recently obtained my Dad's first radial arm saw, made in the mid 60's, don't have the model number at hand but not sure that's important - I tore it down and rebuilt it, corrected the bad wiring (120 VAC), works great, with one problem:

The motor is ancient, of course, has brushes, and no "soft start" capacitors or anything else to slow down the inrush current, which is pretty darn high - when I turn it on, the fluorescent light fixture above the saw goes out momentarily because the current draw is so high - both are on an isolated 15 or 20 amp breaker.

What I want to do, if possible, is to add a startup capacitor to the motor somehow, but not sure how to do it. I found this capacitor for a newer model Craftsman saw:

Start capacitor 124-140mfd, 125 volts | STD376112 | SearsPartsDirect

Start capacitor 124-140mfd, 125 volts
PART NUMBER: STD37611

only $6.50, could be worth a try if I knew how to hook it up (and if it would actually solve the problem) - anyone ever done something like this, have schematics or tips? I'm pretty handy with AC/DC electric wiring stuff, but "electronics" tends to be out of my pay grade ;-)

Would very much appreciate any help/pointers with this problem, as I have a similar problem with my Grampa's old 1937 Craftsman drill press, another strip down/total restore job I also did recently. Tried using a voltage controller on that to slow down the startup, didn't work, motor wouldn't turn over until voltage was high enough to dim the liights above *that* workbench.

TIA to what I hope is an elegant and easy solution!
 
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Old 06-18-14, 06:08 PM
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Unfortunately there isn't an inexpensive and elegant solution. That's a universal type of motor and a capacitor can't be used to soften the start up as there is no start winding. You could use some type of PWM (pulse width modulation) controller but they can run around several hundred dollars depending on where you find them.

Have you considered upgrading the motor ?
 
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Old 06-19-14, 09:33 AM
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Ah, nuts......see, I told y'all I didn't know much about electronic stuff.....didn't know about start windings.....thought brushless induction motors had the soft start built in because of their construction, obviously wrong about that. Replacing the motor is much more work than I want to undertake, alignment issues being the biggest concern - that was the hardest part of the rebuild, getting all 3 axis perpendicular to the table and fence.

Since the saw was free (just my labor and elbow grease), and I don't use it much (prefer my table saw, much safer), guess I'll just have to live with the light dimming, although I assume it's going to take it's toll on the ballasts at some point? Not worried about the electric circuit itself, used 12 gauge wire, so it's not going to overheat.

Thanks for the help, bad news or not ;-)
 
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