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  1. #1
    JeffersonHouse is offline Plastic
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    Default Stanley 677 Grinder Capacitor

    Could anyone please tell me what size starter capacitor a Stanley 677 Grinder uses. When the old one gave out someone in there infinite wisdom simply through the old one out.
    Last edited by JeffersonHouse; 05-12-2012 at 01:26 AM.

  2. #2
    atomarc is offline Stainless
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    JeffersonHouse,

    Welcome to the forum. I don't have an answer for you! I don't think I have ever seen a pedestal or bench grinder in the fractional HP range that had a capacitor start motor. A typical capacitor start motor starts with it's pedal to the metal compliments of the cap. Most grinders wind up very slowly and won't spin their wheel off doing so. Are you sure this Stanley 677 is capacitor start. The pix on the net of this unit doesn't look like it is...but what do I know.

    Edit; I may be all wet on this...maybe the capacitor has such a small value the motor starts slowly but I don't recall hearing any centrifugal switch clicking in/out. I have a nice Baldor but it sure doesn't have any capacitor on board, at least any I'm aware of.

    Stuart

  3. #3
    JeffersonHouse is offline Plastic
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    A local shop informed me that these used a small starter capacitor under the motor, inside the base. I've got several other motors of this vintage that are similarly equipped. I'll be disassembling the grinder in a few days, but not being familiar with its wiring I'm at the mercy of others knowledge.

  4. #4
    wb2vsj is offline Hot Rolled
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    Quote Originally Posted by JeffersonHouse View Post
    A local shop informed me that these used a small starter capacitor under the motor, inside the base. I've got several other motors of this vintage that are similarly equipped. I'll be disassembling the grinder in a few days, but not being familiar with its wiring I'm at the mercy of others knowledge.
    Your local motor repair shop should be able to suggest a cap based on their experience (hopefully they are reputable) and HP rating of the motor.

  5. #5
    atomarc is offline Stainless
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    JeffersonHouse,

    I decided to educate myself a bit on this subject so I pulled the cover plate off the bottom of my 1/3HP Baldor grinder. I found a Aerovox oval run capacitor, 370 volts, 4 MFD. Grainger has these for $6.22.

    Stuart

  6. #6
    Bill D is offline Titanium
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    I think i have that grinder. the cap was bad on mine. I could spin it by hand and then turn it on. It slowly got spinning. bad bearing. I could not read any useful info off the cap before I tossed it. I will check in the morning since a bought a second one at a flea market.. the modern cap will be much smaller. the old one is the size of two paperback books. Make sure you get a run cap not a start one. That model was produced 1930?- 1937. I would expect it has pcb's, or maybe they did not make them yet?
    Does yours have the cap mount bar? If not I can describe
    I am still working on getting the first one's shaft straight. It is all apart in case you need inside info

    Bill D.

    is this the one


    VINTAGE STANLEY 7" BELT PEDESTAL GRINDER BUFFER POLISHER & WHEELS 115V | eBay

  7. #7
    JeffersonHouse is offline Plastic
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    I'd love any assistance you could provide and yes that grinder on eBay looks just like what I've got. I apologize for the delay in responding. I dislocated my wrist this weekend and that stopped me cold from doing anything (very right handed).

  8. #8
    Bill D is offline Titanium
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    There are two different wiring methods. One has two lights that come on with the motor. the other has no lights.
    As I remember there are two motor winding tied together direct to neutral at one end. At the other ends one goes to the switch the other through the cap to the switch. So the cap is in the circuit all the time the switch is on.
    I can measure resistance to figure out which is which.
    The cap mount is a sheet metal strip about 1+1/2 inch wide. bent up at 45 degrees at each end. it runs front to back centered in the base. two small screws hold it at each end. the the cap sits on top banded to the strip. The bearing are a standard size, originals are shielded not sealed.
    Bill D.

  9. #9
    JeffersonHouse is offline Plastic
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    Were you able to find any printing on the capacitor of the grinder you just acquired? It was explained to me at a local motor shop that horse power has little to do with capacitor size. Size is effected more by the gauge of the windings. If I'm off by more than 10% the motor will overheat.

  10. #10
    wb2vsj is offline Hot Rolled
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    Overheat? This is a starter cap, right? Start capacitors stay energized long enough to rapidly bring the motor to 3/4 of full speed and are then taken out of the circuit. You are talking about a couple of seconds (which if you started this thing multiple times every day over a long period of time may reduce motor life). Now if it were a run capacitor...definitely would be harder on the motor.

    BTW - A Caps normal tolerance is usually +/- 10% (I forget the exact numbers, I think it's worse than this).

    Walt

  11. #11
    atomarc is offline Stainless
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    Walt....it isn't a start cap, it's a run cap! That grinder has no switching mechanism inside to accomplish what you describe. These grinders don't 'rapidly start', they crawl to full speed in the proper rotation using a small RUN capacitor.

    Stuart

  12. #12
    JeffersonHouse is offline Plastic
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    I just got this thing apart and we were all wrong. It is definitely a 'start' capacitor. The first thing I saw when I removed the armature was a centrifugal switch. So now I'm back to the original question. What size "Start Capacitor" do I use for a 'Stanley 677' ? Or, How do I size a "Start Capacitor"? When this is all worked out I'm going to post the results and schematic because there are to many of these out there not to have someone else face this problem.
    Last edited by JeffersonHouse; 05-22-2012 at 01:31 PM. Reason: less confusion

  13. #13
    atomarc is offline Stainless
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    Well hell........I guess I had my head where it isn't sunny very often!

    Stuart

  14. #14
    JeffersonHouse is offline Plastic
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    What can I say, this whole thing has me confused. After questions on several forums and all the motor shops in the area everyone assured me 'No' fractional grinders ever used start capacitors.

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