What you're describing *is* the outer case of really old capacitors (especially electrolytics), so it's good you didn't try to open it up. Capacitors that old are almost guaranteed to be bad, so it would be worth replacing if you can find one. Note that caps usually have a pretty broad tolerance range (often -20% to +80% of stated value), so you can often get away with one that is close to the stated uF value, provided that the voltage rating is at least the same as the one being replaced.
Show us Your Vintage Bench Grinders!!!!
- Thread starter 48James
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austin870
Member
How do I find a new capacitor if there is absolutely zero information on the capacitor available? I don't even have a starting point for the 20/80 rule. There might not even be any information inside so if I took it apart. With it working fine I could then be screwed. Someone here replaced the capacitor in their prewar Craftsman but they didn't remember any of the values. You can probably tell electronics is not my strong skill.
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torqueman2002
Well-known member
What about removing it from the circuit and testing it's value? You'll need to disconnect one lead and then use a DMM. Use caution, if it is storing a charge, it can deliver a nasty surprise - discharge it to be safe.
How to measure capacitance - https://www.fluke.com/en-us/learn/b...measure-capacitance-with-a-digital-multimeter
If you make your way over to OWWM website's electrical section, there may be a post and/or a member who has direct knowledge of your model. link - --> http://owwm.org/
Try some of the links Google suggests when you search "how to determine capacitor size needed".
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austin870
Member
Thanks for the info. I was told by a capacitor manufacturer/distributor the values from a 70 year old start capacitor would not be reliable. They would be better than nothing but not much. They also said older ones would have significantly different values than more current ones given same horsepower, phase, cycles etc. I guess I have to fish around more to find some information. Luckily it is working fine right now.
torqueman2002
Well-known member
What he needs is a starting point. Then he'll need to do some trial and testing.
"A single phase AC induction motor will not spin inherently, there are no relative rotating magnetic fields, there are just two fields that are expanding and contracting. The rotor may eventually spin, but the direction will be random and the acceleration will be so slow that you likely will not get it to full speed before the windings burn out because of excess current. So to START an AC induction motor spinning in a CONSISTENT direction, they use several tactics, several of which involve capacitors. I'm not going to go into detail on that here, that's what search engines are for. But the upshot is, the capacitors are generally used to create a delay in the formation in one of the magnetic fields by virtue of the Capacitive Time Constant, which states that a capacitor can only charge at a specific rate. So in the motor, by placing a capacitor in one set of windings, the delay it causes in the resulting magnetic field created by that winding makes for a relative shift in timing of that field getting to full strength. The winding that gets power first induces the rotor to create it's own field, the stator field that gets to full strength a few cycles later makes it repel the rotor field and start spinning. Once spinning, the process perpetuates itself, that's why the starting capacitors are taken out very quickly.
As to sizing, as was mentioned it is all over the map, because the motor designer has to take into account the rotor mass, friction, windage, torque requirements, magnetic permeability of the laminated steel cores of the stator and rotor, wire resistance, etc. etc. etc. In most cases when a NEW motor design is created, this is actually determined by testing, essentially trial and error. Remember, for them, they only need to do that once, then repeat a million times.
There are sometimes two sets of caps in a single phase motor, a Start cap and in some designs, a Run cap. Start caps can be +-10% of whatever was selected, they are not in the circuit very long. In fact, some motors, like refrigeration motors, sometimes have options tor "hard starting caps" that exceed that +10% value to take care of the need for higher torque because of having to start against a closed head. The trade off is added motor heat, but in refrigeration compressors, moving heat around is what they do! But doing that on everyday motors can cause premature failure, so stick to the +- 10%.
Running caps MUST be the correct size, otherwise you can kill the motor windings by over or under exciting them continuously. Over exciting causes increased heat with no increase in work, which eventually cooks the insulation; under exciting causes a loss of torque at the square of the decrease in relative voltage, so the motor under performs and overloads."
https://cr4.globalspec.com/thread/17240/CAPACITOR-SIZES-FOR-CAP-START-and-or-RUN-MOTORS
I recommend he head over to OWWM's Everything Electrical. There's a wealth of experience with these vintage motors.
"A single phase AC induction motor will not spin inherently, there are no relative rotating magnetic fields, there are just two fields that are expanding and contracting. The rotor may eventually spin, but the direction will be random and the acceleration will be so slow that you likely will not get it to full speed before the windings burn out because of excess current. So to START an AC induction motor spinning in a CONSISTENT direction, they use several tactics, several of which involve capacitors. I'm not going to go into detail on that here, that's what search engines are for. But the upshot is, the capacitors are generally used to create a delay in the formation in one of the magnetic fields by virtue of the Capacitive Time Constant, which states that a capacitor can only charge at a specific rate. So in the motor, by placing a capacitor in one set of windings, the delay it causes in the resulting magnetic field created by that winding makes for a relative shift in timing of that field getting to full strength. The winding that gets power first induces the rotor to create it's own field, the stator field that gets to full strength a few cycles later makes it repel the rotor field and start spinning. Once spinning, the process perpetuates itself, that's why the starting capacitors are taken out very quickly.
As to sizing, as was mentioned it is all over the map, because the motor designer has to take into account the rotor mass, friction, windage, torque requirements, magnetic permeability of the laminated steel cores of the stator and rotor, wire resistance, etc. etc. etc. In most cases when a NEW motor design is created, this is actually determined by testing, essentially trial and error. Remember, for them, they only need to do that once, then repeat a million times.
There are sometimes two sets of caps in a single phase motor, a Start cap and in some designs, a Run cap. Start caps can be +-10% of whatever was selected, they are not in the circuit very long. In fact, some motors, like refrigeration motors, sometimes have options tor "hard starting caps" that exceed that +10% value to take care of the need for higher torque because of having to start against a closed head. The trade off is added motor heat, but in refrigeration compressors, moving heat around is what they do! But doing that on everyday motors can cause premature failure, so stick to the +- 10%.
Running caps MUST be the correct size, otherwise you can kill the motor windings by over or under exciting them continuously. Over exciting causes increased heat with no increase in work, which eventually cooks the insulation; under exciting causes a loss of torque at the square of the decrease in relative voltage, so the motor under performs and overloads."
https://cr4.globalspec.com/thread/17240/CAPACITOR-SIZES-FOR-CAP-START-and-or-RUN-MOTORS
I recommend he head over to OWWM's Everything Electrical. There's a wealth of experience with these vintage motors.
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Gzuz
Member
I just made created my first thread/post but here's a picture of the bench grinder I recently picked up
https://photos.app.goo.gl/pEYstWGMTi7pX3LKA
https://photos.app.goo.gl/pEYstWGMTi7pX3LKA
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Tylermorris
Well-known member
cmccuist1
Well-known member
Ever since I saw Nortonscustoms big *** Cincinnati grinder (attached) I've been looking for something similar.
I finally found one on Craigslist and pulled the trigger. I know I paid too much for it, but it's just so awesome I had to have it. This will go well with my 8" Craftsman block and my 10" Thor.
It's a 12" Queen City, 3hp, 3 phase. It's missing the eye shields and a part of one of the guards, but I think I can fab a part to cover that up.
I finally found one on Craigslist and pulled the trigger. I know I paid too much for it, but it's just so awesome I had to have it. This will go well with my 8" Craftsman block and my 10" Thor.
It's a 12" Queen City, 3hp, 3 phase. It's missing the eye shields and a part of one of the guards, but I think I can fab a part to cover that up.
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bagged89s10
Well-known member
so I bought this 1HP black & decker grinder on a stand. As I wheel it out to my truck with a hand truck and put it down on the gravel, it falls over and the mounting tabs crack off. And a crack on the left side. Is it worth trying to braze back together? I either try to repair and the sell it or sell it as is.
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Don't forget the cracked wheel guard and the left side. That material looks so thin and flimsy I don't see how you could repair it with brazing. Good luck, but I think you now have a boat anchor.
bagged89s10
Well-known member
bagged89s10
Well-known member
i’ll experiment braze aluminum on it but most likely i’ll probably just part it out. some of the parts look similar to a craftsman block but i’ll have to compare later today.
Man that awesome! Do you have projects that require the wheels that far apart or so you just like em that way? [emoji39]
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cmccuist1
Well-known member
I like the wheels that far apart. you can stand right up close. I was going to try and powder coat the arms and guards, but I don't think I can get those arms in my oven!
454ragtop
Well-known member
I wonder what kind of magic is in that B&D grinder to produce 1 HP on 7 amps...…..
Me thinks they may be stretching the truth...…...
Me thinks they may be stretching the truth...…...
PeterPeter
Well-known member
Here's my first post here guys, so be gentle :^)
Ok, it's not a grinder, but it's a pedestal for a grinder. I got tired of looking through the thread, so I cut to the chase: anyone have the grinder that goes on top of this beauty? Or how old it might be? Sure doesn't look like any Black and Decker I've ever seen. It has the B&D logo embossed, and on the foot says B&D 625
Ok, it's not a grinder, but it's a pedestal for a grinder. I got tired of looking through the thread, so I cut to the chase: anyone have the grinder that goes on top of this beauty? Or how old it might be? Sure doesn't look like any Black and Decker I've ever seen. It has the B&D logo embossed, and on the foot says B&D 625
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PeterPeter
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PeterPeter
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PeterPeter
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Will McRay
Well-known member
- Joined
- Oct 20, 2013
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davethorik
Well-known member
davethorik
Well-known member
Thanks to a tip, I believe these JC Penney grinders were made by Baldor. I also think the E in the one part number stands for "extraction"- check out differences in side covers and guards. The E model side covers are much thicker. Edit: also, it looks like the spark arrestors are only there on the non-E model. Oh well.
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chrisnazzy
Well-known member
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davethorik
Well-known member
Yes I'm happy about that, always thought Baldor would be a luxury brand, but this was a nice surprise. I've seen jc Penney ratchet and socket kits but never a bench grinder.
Grindyguy18
New member
I have, and it was in a lineshaft shop, not that new fangled techonology you seem to be running.
PeterPeter
Well-known member
I can smooth out wooden spoke wheels for my tin lizzy faster than you can say dad-gum with this here grinder.
Everything old is new again. Peter
PeterPeter
Well-known member
Oops. I did it again. Came home today with one of the most unique Craftsman grinder 410.16990. 8amp, 3/4 HP, 8"? wheels, complete, and lightly used, made by Brown and Brockman, the maker of the legendary B-Line. Anyone know when they made these?
Pinch me, I think I'm dreaming.
Pinch me, I think I'm dreaming.
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Straightgrain
Well-known member
I think you mean "imported by Hartford Machine Tool". That grinder screams Asian-made to me.
Agree, the rotation direction stickers really sell it for me.
Straightgrain
Well-known member
Have you ever seen an Asian import with "Los Angeles, California" stamped on the manufacturers plate?
454ragtop
Well-known member
Note it doesn't say "Made in Los Angeles, California". Those stamped tin wheel guards also scream Asian import.
PeterPeter
Well-known member
A quick check of the Vintagemachinery.org site finds no Hartford Machine Tool listed, in LA or anywhere else
Dibiase77
Well-known member
trijeff
Well-known member
Looks like a Wissota made unit, nice pick up
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Dibiase77
Well-known member
This is my first grinder. Sorry for the naivete. What is wissota?
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