Finally upgrading to a "real" grinder!

[DaveSmith]

I've got a brand new 2x72 Coote slapped together. I didn't want to mess around, so I just snagged a 3hp motor (3450 rpm).

 

That's a pretty high rpm, but I should be able to control that just fine with the appropriate pully choices, right?

 

Also, I've read that the linked drive belts are absolutely the way to go. Is that a generally shared opinion?

 

Another reason I created this thread was to keep all my questions confined to one place... after the appropriate search attempts, of course. So, expect more questions.

[Doug Lester]

That's the speed of my motor and I put a 1 1/2" pulley one the motor and a 5" pulley on the grinder to slow it down enough for the finer grit belts. I just went to 40 grit belts to speed up the rough grind.

 

Doug

[J.Arthur Loose]

Bolt that baby down good... I'm sure you've seen the recent Coote thread:

 

http://www.bladesmithsforum.com/index.php?showtopic=20319

 

Putting the grinder on a solid piece of 1/2" plate and adding the linked belt have made it totally solid.

 

I know that the recommended speed is 1700 RPM... I'd wonder if running it too fast could burn out the bearing. I know that the back-mounted small contact wheel assembly wants to run at the absolute slowest speed to prevent damage to the bearing, but it's a smaller kind of bearing.

 

I've got a 1 HP 220 volt motor and it seems just fine. 3 HP is going to be a force to reckon with!

 

Have fun,

[B Finnigan]

I break plenty of belts with a 1 1/3 HP grinder so I never saw a need for anything bigger. And mine goes up to 1800 but I rarely use that speed because there is a lot of heat produced even with a brand new belt. My learning curve has shown slow and easy is the way to go. Fewer mistakes, bloody knuckles and expensive belts.

[DaveSmith]

Okay, when I said "more questions"... I meant it.

 

After reading what people had to say about 3hp in various places, and realizing that the motor I bought was set up for 240v only anyway, I opted to take it back and replace it with a 2hp motor (Here's the motor).

 

Let me start by saying that I fall far short of being an electrical whiz. I hooked up the power cord (14g) as per the wiring directions that came with the motor. Some wires went to line 1, some to line 2, and the rest to ground (those wires were then clamped under the appropriate bolt as specified in the directions). How do I know which wire in the cord is line 1 and which is line 2? Does it matter as long as I have the ground correct? I assumed black was ground, and the other two wires could be line 1 or 2 indiscriminately.

 

When I went to plug it in, there was a spark and the motor turned on for about half a second, then stopped. When I pulled out the plug, the copper was melted a bit.

 

I checked the breaker and it had flipped (but the next try, it didn't). The breaker said it was rated for 20 amps, so I figured that wasn't the issue.

 

I tried a couple different outlets, and a similar thing happened. Now those outlets don't work, but everything else connected to that breaker still works.

 

Any clue what I'm doing wrong?

 

Where can I get a relatively inexpensive motor that's already wired so I can just hook it up to the dang grinder?

 

Any other useful info/suggestions?

[Alan Longmire]

That motor can be set up for either 110 or 220, and there will be a diagram for each. The setups are NOT interchangeable, and your description of line 1/ line 2 sounds like you used the 220 diagram. Oh, and the green wire in the cord is ground, and if running 220 both black and white are hot. If running 110, white is hot and black is neutral, green becomes equipment ground. I just switched my own motor over to 220, and in so doing I learned they lied about the wire color that makes it run CCW versus CW. The diagrams did not say which specific voltage they were for, rather they had in very faint print "high line" and "low line"

 

On the fusebox end,a 110/115 breaker will have the white wire hooked to the breaker and the black to the grounding bus, green is tied off to the panel out of the way on a separate ground bus. A 220/240 breaker has two poles (looks like two breakers glued together with a bar connecting the switches), takes both the black and white wires (one per side, not in the same clamping hole!) and green goes to the main ground bus.

 

If you didn't let the magic smoke out of it when you hooked it up, you may want to return it for another reason: That one has an open case, which means it will fill with grinder dust and grit, which is rough on the motor. Grinder dust is both abrasive and conductive, so it both ruins the bearings and makes for shorts in the motor windings. Look for a motor marked "TEFC," or Totally Enclosed Fan Cooled. They were made for that type of application. They're a little more expensive, but worth it since they'll last more than a couple of years.

[Brian Madigan]

I'm using 1/2 hp 110 volt 1475 rpm motor on a KMG grinder. I'm running a slight reduction pulley, and I've never had a problem with it bogging down.

I have a few 1hp motors, but I don't find the extra power necessary. My whole shop is runs on a pair of 20 amp slow-blow fuses, so I like to keep the motors below 10 continuous amps. When starting up loaded, a motor will usually pull more amps than when running at speed.

If you're frying outlets, try plugging them into a cheap power strip with a built in resettable breaker. The strip should load and trip at lower amperages than the outlets or main breakers will.

http://www.acehardware.com/product/index.jsp?productId=4001344&cp=2568443.2568454.2632223.1259253

 

I have everything in the shop on strips like these; 15 amps is enough for most motors up to 1 hp.

[Alan Longmire]

Brian, I don't know how you do it with a 1/2 hp motor, I can stop my 1 hp when it's on the high-speed pulleys... I do have to lean on it, but I can stop it dead. Well, that was when it was on 110, I haven't had time or occasion to try it now that it's on 220.

 

Dave, after reading your question again, it seems I was typing too early and didn't bother to explain what happened.

 

IF you hooked it up for 110 in the wiring box on the motor but used the green (or bare) wire for one of the non-ground lines, what you did was cause a direct short-circuit to ground. The outlets no longer work because you probably vaporized the connections inside them. This can have implication for your circuit elsewhere, as it suggests you may have a ground fault somewhere in the system.

 

If I were you I'd hire an electrician and tell them what you did. You'll need a few new outlets anyway, and you may even want a dedicated line put in for the grinder. It shouldn't cost a heck of a lot, and you'll have peace of mind knowing you aren't about to burn something. Oh, and get a switch for the grinder, it's not a good idea to control it by just plugging it in and unplugging.

[B. Ellison]

If I were you I'd hire an electrician and tell them what you did.

 

^

That is the best advice ever. If you are not familiar with wiring a motor, having a qualified person come out is a small price to pay to avoid personal injury or further damage to your property.

 

Also, Beaumont Metal Works has motor-mounted toggle switch kits for $38: http://www.beaumontmetalworks.com/110089-setup.html

 

ETA, short clip of motor-mounted toggle switch:

 

Congratulations on the Coote, and be safe.

Edited October 18, 2011 by B. Ellison

[Sean McGrath]

it's not a good idea to control it by just plugging it in and unplugging.

No, it's not. I was doing that with the 1 1/2hp 110v motor on my KMG, and while it did work, the instant draw ended up blowing the end off one blade of the plug, which also ruined the outlet. I ended up leaving a plug on it, but cut the cord in half and ran it through a common light switch. The switch is only rated for 15 amps, but so far I haven't had any problems with it. However, I don't generally put heavy loads on it, and the switch may very well fail if I do so.

 

Whatever you do though, operating it simply by plugging it in and out of a wall socket isn't a good idea.

[Alan Longmire]

Mine is controlled by a standard 15 amp light switch mounted in a metal "handy box" type switchbox bolted to the front of the motor wiring box door. Works fine, even on 220. All you have to do is cut the white or black wire and run it through the switch terminals, leaving the other two wires intact at that point. This works for both 110v and 220v, no need to spend the extra $20 to find a dedicated 220 toggle switch. I think the wiring, switch, handybox, switchplate cover for said box, and a plug terminal set me back about $10. That's just the part between the motor and the wall, of course.

 

Oh, and seal the box with a foam gasket or electrical tape to keep out that darned conductive dust.

 

I used 14/3 wire and ran it into a wall socket. I did put a new 220v outlet in, and just switched out the plug end for one that fit.

 

Wiring can be simple, but it is extremely unforgiving of mistakes. You can easily electrocute yourself with a bad ground (makes every metal part of the grinder hot!), and a single poor connection can cause a fire. You may want to discreetly check your local codes as well. I just had an electrician upgrade my old 100-amp fused main house service to 200 amp breaker service, and while he was here I was talking about how I did the grinder and the power hammer and the other stuff I've run from the subpanel in the studio. He told me that if I were inside city limits (I'm about half a mile out) that would have been illegal and I could face fines for doing my own wiring in my own building! Gotta watch those darned bureaucrats as well as stray electrons.

[DaveSmith]

Okay, so my buddy wired up the motor for me... it purrs now. When he told me how he did it, it seemed so simple. The instructions that came with it were just a bit vague (at least... that's what we'll blame it on).

 

The grinder stand is built, so in the next few days I'll get to slap everything together and see how it works.

[DaveSmith]

Thanks for any and all advice. The grinder is working great now.

 

My newest issue is that I have cheap belts. I'm thinking I'll notice a huge difference if I upgrade to some of the Trizact "Gator" belts.

[Alan Longmire]

You will indeed notice a difference, especially on the higher grits. Get some normal GOOD belts for hogging and profiling, and use the Trizacts for finishing. I like the Norzon ceramics and the Klingspor blue zirconia belts in 36 to 80 grit, and Trizacts for everything above that, except for handle work. For handles and other wood I like the Klingspor gold J-flex belts in 220 and 400 grit. Trizact belts do not work on wood, nor will they work wet.

 

Also remember Trizact grit size is listed in actual microns, not screen number. This means the higher the number the rougher the grit, which is the opposite of "regular" grit sizing.

 

I like to start with an A300 after the 80 grit blue Klingspor, followed by A120, A65, and A45, then go to hand rubbing with 220 through 400 grit wet-or-dry paper lubed with synthetic motor oil or windex, depending on the material.

[DaveSmith]

Thanks for the advice Alan.

 

The gator belts should arrive tomorrow, so I'll pop in real soon and let everyone know what I think.