Grinder Motor for Garage Shop

Adiniram7

Adiniram7

Joined
Dec 19, 2005
Messages
28
olks,
I am looking for a 1 hp/3400 RPM or better TEFC motor to power my 2 x 132 knife grinder. Got it on ebay, amazing find. Looks like the ones in RW Wilson's shop that he makes. The caveat is that I need a motor that will run on a standard Nema 5-15 (15A 125V) power circuit. I don't havethe investment capital for the electrical work required to run my current 20A 115V motor. Could you recommend a model that would suit my needs? Or, any one have experience getting a 20A 115V motor to work on a Nema 5-15 15A 125v circuit?
 
I doubt you will find a motor powerful enough to run on 110 15 amps. It would be cheaper to run the wire yourself and use your existing motor, which still might not be strong enough for what you will ask of it.

Rewiring your shop isn't all that hard, but you need to make sure you know exactly what you are doing.
 
You're looking for a 3400 rpm motor... what size is your drive wheel on that grinder? If it's 6" or larger, I'd recommend a 1725 rpm motor. At a 6" drive wheel, 1725 rpm will yield 2708 sfpm. With a 3400 rpm motor, you'd get 5338 sfpm. That's FAST for general purpose- I've known people to rough grind that fast, but nothing with much finesse. A 4" drive wheel at 3400 rpm yields 3558 sfpm, or about as fast as I'd want in a single speed grinder.

Also, have you tried running your 20A motor on your 15A circuit? Is it installed in the grinder, so that you could try to start the motor with a belt (load) on the motor?

I had a grinder at my Maui shop that had startup draw too heavy for the breaker. It was an old Square Wheel grinder. It would start with no load however. So, I'd keep the belt loose, start the motor, and immediately tighten the tracking/tension arm when the motor came up to speed.

The fact that it was a Square Wheel with a dust housing made this a bit more safe than it would be on other grinders. I don't necessarily recommend this, it's just what I did to make it happen for a while. Starting the motor is where it draws the most current, after that it drops and levels out. Maybe try spinning the contact wheel by hand with a belt installed just before you flip the switch.

If you have tried the grinder on your circuit and it doesn't work, maybe try to find a 20A outlet somewhere and make sure the motor actually does start up fine. You never know, you could have a blown start capacitor or something. If you can spin the shaft/drive wheel hard by hand, flip the switch and then it starts, you probably do have a cap problem.

Is your chosen spot for the grinder anywhere near a 20A outlet? perhaps you could use a heavy extension cord if the wire run wouldn't end up being too long. Does your shop have its own breaker subpanel? Is your wiring fairly exposed? There are circumstances in which is really pretty easy to add a circuit yourself.

I guess all this is my way of saying that if I was you I'd look for a way to make your 2hp motor work. For a grinder with a 2" belt width, 2hp is much nicer than 1.

Just my $.02. Someone will probably post after this about how I'm giving you dangerous advice and never to mess with electricity, go by the book and don't risk your home and shop. And they may even be slightly right. :rolleyes:
 
I have found that a 1 hp 3400 rpm motor draws 12 amps which is appropriate for a 15 amp circuit.
but the same 1 hp in 1700 rpm is over that and will trip a breaker.



I can't recommend a motor without knowing your mounting style

I couldn't find any info on that grinder either.

56 frame?
C face, or base mount?

Giving you a model # won't help much unless you go buy that motor new.
There are hundreds of motors that would fit.

You are better off searching ebay or something for a motor with the specs you need.
 
If you have 12 gauge wire on your 15 amp circuit you can just change to a 20 amp breaker. Many circuits are run that way, at least around here. If you have 14 gauge wire don't upgrade the breaker without pulling a bigger wire. I don't know of a 15A 1hp motor.
 
Another critical detail to remember when sourcing a new motor is shaft size. It should match your drive wheel. If you really have to, you can bush a motor shaft or bore your drive wheel hub, but try to avoid that like the plague.
 
Thanks for the replies guys, they are informative. So far I have been making knives with an Angle grinder, files and a little 1" Harbor freight grinder and a LOT of elbow grease and patience. All I knew about grinders is that 1) I needed one. and 2) I can't afford a $2000+ pricetag, so I jumped on this grinder when I found it. (link below) I'll try to hit the queries in order:

Salem: You're looking for a 3400 rpm motor... what size is your drive wheel on that grinder? If it's 6" or larger, I'd recommend a 1725 rpm motor.
- I think it's a 6". Thanks for the heads up.

Also, have you tried running your 20A motor on your 15A circuit? Is it installed in the grinder, so that you could try to start the motor with a belt (load) on the motor?

- No I haven't yet. What I read so far sait that it would be a no go.

- As for the 20A circuit on the house, there is one in the kitchen but it would require investing in a 100 foot extention cord to run out to my detached garage. The cord is the price of some motors I've seen. So if I were to spend that much I though it a wiser investment to just buy a brand new motor and know that it will work in the garage as opposed to the used one that I was told ran fine, but have not been able to start. There's nothing in the garage outside two 15A sockets.

1-10
It's a base mount.

Woodsman
- Interesting, I'd have to look. Any WWW how tos that you would recommend?

Thanks Guys!
http://www.ebay.com/itm/KNIFE-MAKER...=LH_DefaultDomain_0&hash=item4aae93f46e#payId
 
If none of the other suggestions work out and you find you really do need a new branch circuit and can't afford an electrician, perhaps you could swap favors with someone who knows how to route a new branch circuit? Make them a knife or do some other favor for them?
 
Nice find on the grinder!
This is just my opinion, but I'd try to adjust the electrical supply to fit the motor. Also some motors have two ways to hook up, a 110 volt connection regimen and a 220 volt connection regimen. Usually there will be a little diagram next to the plate that the wires enter the motor from. I believe that if you use 2 wires for the 'hot' wires in 220 (220 is superior to 110 even though it works out electrically the same) that would be good for 20 amps, but if you used that same gauge wire in a 110 volt design-one 'hot' wire and one neutral , it WOULD NOT be good for 20 amps (need 12 gauge or bigger). With 220 volts, you are 'sharing' the current, with 110 volts, I don't believe that you are. You also need a ground wire in either 110 volt or 220 volt. The distance from the breaker to the motor is significant if it's over a certain amount, say 40 feet or so. If you have a Home Depot, or Loews, they frequently employ a electrician in the electrical section of the store, you can call them and ask if they have a electrician on duty that day. They will try to avoid getting themselves in trouble legally (after all they aren't making any money off your advice) but they can tell you how to do the hook up if you (and they are too) are patient. It's really just a question of looking at a chart and seeing where your variables of load and distance meet where it will show you what size of wire you need. That and doing the connections and other things (like grounding) according to code. Another resource (if you own the house) is to get a permit-when the inspector comes out, he will make sure everything is 'kosher'.
Also, I think much of the cost of running another wire (or a bigger set of wires for maybe a sub-panel?) is the digging and placing of conduit (I think it usually needs about 18" deep unless you put a shovel of concrete on the conduit to protect it (maybe a couple or 3 inches thrown on top before covering it with dirt again) and putting a string or wire to pull the fish tape through later. You could route the conduit into the garage and put it into a electrical box that will be the place where you eventually get power from, and also route the wire into the service entrance (make sure you turn off the power before working in the box and understand that even when the switch is off in the panel, there are STILL places you can be shocked if you are not aware of them)
If you are careful and use the pulling 'jelly' (slippery to avoid damage from friction) you could place the wire, and when an electrician comes out, they would only have to charge you a maximum of a hour to do the hook up, if you have all the parts (breaker, etc.) on hand and have done all the 'grunt' work for them.
Another reason for adjusting the voltage to fit the motor and not vice versa, is that if you ever plan to have a heater, or some other shop tool(s) out there, you will have the electric capacity already, and it will be merely a job of running a couple more wires!
Good luck and congratulations on your ebay find!
 
To check your wire size:

A. TURN OFF POWER TO THE SHOP. Flip the breaker that goes to the outlet you will be testing. Then, check to make sure it's off with a volt meter or at the very least, an appliance that you KNOW works.

Take the faceplate off the outlet. Unscrew the top and bottom outlet mount screws. Pull the outlet out enough that you can unscrew one of the wires from a terminal. Measure the end with a micrometer or calipers- 12 gauge wire is .080" dia., 14 gauge is .064" dia. Another common but slightly less reliable way to tell is that 12 gauge wire will be in a yellow sheathing, and 14 gauge will be in a white sheathing. This is now standard, but was not always so. Or, you can use your wire strippers to check your wire gauge size. The correct gap will be slightly larger than the copper of your wire.

Digging your own ditch and installing conduit is not a bad idea- maybe have a conversation with an electrician about what you exactly want for power in your shop. I've installed long runs of conduit and heavy wire before- no need to "fish" it through per se, you can run conduit sections down over the wire pretty easy before you glue them together. No lube necessary.

Nice score in the grinder.
 
I think the general concensus is that you need more power rather than a smaller motor. Save your pennies until you can afford it. I have learned the hard way that if it worth doing, it's worth doing right, which usually cost more $$$
Jason
 
Ok all,

I think what I will do is temporarily run an extension into the house where there is a 20A outlet. (The ones in the garage won't handle 20A at all right now, so I will have to get that run from the main breaker.) Once I sell my first 10 or so knives (well, at least sell for full price to ppl who aren't close friends that I didn't want to charge fully for my practice knives) I'll get the garage wired.

I'll keep you posted on the progress. I'll also post some shop pics where appropriate here too. Salem - Your site is AWESOME. How the heck did you forge a rose???

Anyway guys, sage advice. Thank you.
 
Another thing that might help is filling out your profile to let us know where you are, you might find another maker pretty close to you that is willing to come over and help you get set up.
 
Thanks, man. A rose ain't too tough, and they get better with practice. Lot of torch work.

Mike's right, it's good to fill in your profile if you plan to hang out here a lot, I hope you do as it's a great resource for a knifemaker of any skill level. Good people here too.
 
I have an air compressor with a 20 or 21 amp 2hp 110v Baldor motor. It takes very little time and effort to put a 20 amp breaker in, and it has never tripped the 20 amp breaker. It won't run long on a 15 amp breaker. On 14 guage wire, I know it's not the best, but I bet it would work perfectly fine. Lots of houses are wired with 14 guage 20 amp circuits. It isn't normally the way it is done any more.

You will lose voltage running a cord. That's what normally fries motors, is the voltage drop.
 
Mike Davis said:
Another thing that might help is filling out your profile to let us know where you are, you might find another maker pretty close to you that is willing to come over and help you get set up.
Click to expand...

Thanks Mike. I put a little about myself on my profile, including my name and company name. Take care.
 
Salem Straub said:
Thanks, man. A rose ain't too tough, and they get better with practice. Lot of torch work.

Mike's right, it's good to fill in your profile if you plan to hang out here a lot, I hope you do as it's a great resource for a knifemaker of any skill level. Good people here too.
Click to expand...

Thanks guys. I put some basic info down. More to come when I actually get a site up. I'm in Northern VA though, right outside DC. "Rose ain't too tough" modesty is a good quality....
 
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