Suffering for my art...Owww!

J. Neilson

J. Neilson

Joined
Feb 6, 2001
Messages
3,621
OK, I've got a question for you electrical or science gurus out there. I've got one of my Grizzly grinders shocking the hell out of me.
COLD%20SHOP-GRIZZLIES.JPG

The Griz on the right is the one I use for hogging profiles and all rough work. When I'm using it you can see (and feel) it arcing right from the platen, around the belt and into my work piece and me. Now I don't mind a little shock every now and then...keeps the old heart going but, this is getting out of hand. I'm now getting zapped on the grinder and again when I go to cool a piece of metal in the water bucket. Big zaps now, it's actually arching out of the bucket. Two for one. The maching has a grounded plug, I've tried a rubber mat, rubber soled shoes, the outlet??? This started as cold weather set in so I thought it was a static charge since it happens on occasion with other machines but, this one has gotten totally out of hand. Help! I've got way too much hair to have it stand on end like this.
 
Check you ground plug and make sure it really IS grounded. Mine did that a while back when I had it hooked up to a varistat. Blew all the metal dust out of it and it quit.
 
Is that a concrete or wooden floor, J? You can physically ground your machinery to an earth ground and that will help dramatically. You may need to buy a ground rod and drive it into th eearth outside your shop. Attach a 12 gauge piece of stranded copper line to your grinder, and the other end to the grounding rod. I've had to use that appraoch many times with the printing presses here. You should see what that static electricity will do to a piece of paper that is supposed to lay flat when it goes through a press!
 
J. is it just static build up with the cold dry air of winter. I noticed a lot more static getting in and out of my truck now and its all because of the super dry air. This is what I do when grinding and statics biting the heck out of me. I ran a ground wire to a steel peg drove about 1 ft. in the ground. I put a little gator clip on the in shop side of the wire and I clip it to my sock against the skin when I 'm grinding, I don't have anymore problems after that. Just be sure that its static elect. and not a short in your grinder motor. Be careful.

Bill
 
First J. Jeff is right. You should have everything to a dedicated ground for safety....but....I don't think that's the problem. You don't normally see arcing like that from normal AC Circuits. It will shock the he!! out of you, but not arc.

I think Bill hit it dead on. I have that happen once in a while when the weather is right. The slack belt grinder is worse than any of them for some reason. Try Bills idea or get an anti static wristband like computer techs use.
 
I've had the same trouble grinding handle material on my 1x30" slack belt. When it gets too bad I put a little chain around my wrist and clamp the end of it to the grinder. I've also noticed the problem is worse when I'm grinding barefoot with my feet in the quench bucket. -chris

__________________
Chris Crawford Knives

 
If I understand your situation correctly, here's what's happening:

The belt contacting the blade is creating a static charge that is being displaced back to you rather than back to earth. This could happen for a few reasons:

1 - you have a insulating platen (are you using pyroceram?)

2 - your platen is small or thin (not enough steel to absorb the extra juice)

3 - your ground (on the motor) is weak or disconnected

4 - your motor is generating static charge (does happen) - more than the ground can handle...leaves a leftover charge at the platen.

5 - (can't think of another one....will come back if I do)



To solve the problem, you want that extra electricity to go back to earth through a metal connection - and not through you.

If you are not using a pyroceram platen, then you can just simply connect a 10ga wire with alligator clips from the platen to any large piece of unpainted metal or concrete or a rod buried in the ground. The current wants to get back to earth and will take the path of least resistance. Humans contain a lot of water...and make great capacitors (store electric charges). So, buy not having a proper ground, the charge is building up inside you and discharges when it find a conducting element....such as a bucket of water, or a piece of steel, or your cat.....(we could have some fun with this one.....:eek: )

Personally, I solved my zap problem by taking an old set of jumper cables (for your car) and clipping one end to the grinder (steel) and the other end to a metal stud fastened to my concrete floor.

You could also get a bigger platen, or weld up a large piece of steel behind your current one to absorb more of the charge. You'll still need a ground, though.


Now, if you have the pryoceram platen, then you're screwed....:D

No, seriously, though.....it does complicate things. Email me if that's the case and I'll try to help you figure it out.


Just remember a few things NOT to do:

1 - Don't buy one of those wrist-strap electronic insulator things.....they're made to protect what you're working on....not to protect you.

2 - Don't ground yourself to anything - just makes you a conductor. You won't get zapped....but if a surge of electricity comes through, you'll feel it then.

3 - Don't wire a ground between machines - each one needs its own ground. They can all go to a common ground, but shouldn't be wired one to the other, etc.



Took some reading and researching to figure this all out, but I no longer get any zaps at all - even if I'm grinding with one hand and have the other in a pail of water = not recommended...but I have done it.....the steel got too hot and burnt the index finger on my left hand (grinding with my right, supporting with left). I reached over and dunked it in the pail before taking the knife off the platen....didn't even think about it until afterwards...but apparently, I had a pretty darn good ground.


Final note - grinding in the slack area will also result in a static charge - because there is no immediate path for the extra electricity. It can travel down the belt some...but only a very small percentage.

There are some who advocate a little WD-40 (or other spray) on the back of the belt - seems to help with the static - I believe what's happening is that the fluid helps carry the charge back to the platen.
 
I used the ground wire in the sock trick. One time the wire wasn't in good contact with the skin - so it arced there. My leg was hopping like a dog gettin' his belly scratched.


Steve
 
copper insoles and quick disconnects :D :D :D


probabably keep you from getting arthritis too.
 
peter nap said:
First J. Jeff is right. You should have everything to a dedicated ground for safety....but....I don't think that's the problem. You don't normally see arcing like that from normal AC Circuits. It will shock the he!! out of you, but not arc.

I think Bill hit it dead on. I have that happen once in a while when the weather is right. The slack belt grinder is worse than any of them for some reason. Try Bills idea or get an anti static wristband like computer techs use.
Click to expand...


I agree
I'll get it from the rubber wheel also and my buffers.
BUT
I would hook the ground wire from out side to the machines also just in case they short out so you are not the complete grounding rod.
if it was AC currant arching that far you'll be dead right now.
it only take 1 amp ac to kill you if you are completely grounded.
the winter dryness is causing it..you'll see you get it worse grinding on bone don't you :D

swaping shoes will help some are better than others. I have felt the spark up through the soals of the shoes. That's cool :D
 
peter nap said:
You just had to know either George or I would do this:

afdbhead.jpg
Click to expand...
YEP!! He should put it on the other head. That way he would save on foil. :eek: He would be lucky if he used a 1/4" square, that's what GrassHoppa told me from his last visit. :D
 
The belt on your grinder is acting like the belt on a Van De Graff generator. The piece of metal that you are grinding is acting like the big dome on top that collects static charge. These are the machines that you see in science museums and bad sci-fi movies producing foot long arcs of static electricity. The failure rate of electronic components, due to static charge, peaks every winter due to the reduced humidity levels, especially in the colder, northern areas.

Daniel is right. Wrist-straps, and other devices that dissipate the static charge on your body, are designed to protect static sensitive devices by, usually semiconductor devices like microprocessors and memory chips not you. They dissipate the static charge gradually rather than just short it out.

Please DO NOT just stick a grounded wire in your sock or around your wrist. It will get rid of the static charge but if an electrical fault occurs in your machinery, you could be electrocuted. It is generally recognized in the electrical/electronics industry that only 5 mA (0.005 Amps) through your heart is enough to disrupt it's function. Those wrist-straps used in the electronics industry have a high-value resistor in series (about 1 MegOhm) to limit the current to a value well below the 5 mA level. Oh yes, the frame of your machine should be grounded for safety. That is one of the things that UL looks for before certifying a piece of equipment.

The solution is to provide a path to ground for the static charge that is of lower resistance than the one through your body.

Making the belt slightly conductive and grounding your machine would do it. There are anti-static sprays meant for use on work surfaces and anti-static floor coatings but they may be hard to get a hold of. Large janitorial supply places might carry such stuff. I have heard that liquid fabric softener works. I don't know what any of these materials might do to your belts. Drawing a couple of pencil lines on the back of the belt, along it's length, might do it.

A method that I have seen used on rotating machinery is to install a strip of something that looks like those tinsel "ropes" that one decorates Christmas trees with. The tinsel rope would be placed so that it brushes lightly against the back of the belt, somewhere. The tinsel rope would be grounded through the chassis of the machine.

One last method used in the electronics industry is to increase the humidity of the air. Arrange a humidifier so that it blows over your grinder. The humid air will provide a path for the static charge to go to the earthed frame of your machine.

There is a whole sub-industry related to dealing with static electricity that is parasitic on the electronics industry.

Hope this helps.

Phil
 
peter nap said:
You just had to know either George or I would do this:

afdbhead.jpg
Click to expand...

dang IG wants to play with my helmet again he's just wishing again.. :eek: ;)


I'm not sure I want to humidifi my shop :eek: but the other stuff sounds OK

Thanks Phil. :D
 
Wow!!! You guys really know your stuff...George, your just a sicko. ;)

I double checked the ground for the shop...the shop has it's own breaker box and ground, that was good. Double checked the outlet and machine ground for both connection and dust...good. It's funny that it's only this machine though. I get nothing slack belt grinding on it. I'll try some of these suggestions..except for a few :rolleyes: ...and let you know. By all means, keep them coming. I'm going to print and save this for future reference, no doubt.
 
hmmmm I wonder if you'd get any changes if you wire the two grinders together. grounding wire?


OR
if you are on an old Indian burial ground you may be standing on someone's head move the grinder and problem solved. :eek: :D
 
J

The rubber on your contact wheel may have a bit of metal dust stuck to it making it a bit conductive an allowing the static charge to bleed away.

Slowing down your grinder should help reduce the static build up too.

Is it just my imagination, or was last winter the last time that someone posted about this topic? It also seems that it was the makers in the areas that get really cold and dry winters that noticed this, not those in places like Texas, Georgia or Florida. It would be interesting to hear what George Tichbourne has to say about this topic since he lives in the Toronto area (very cold and dry winters) and he has run a metal polishing business for many years. I am guessing that he has/had multiple grinders/linishers in addition to buffers.

My wife just saw the picture that Don (Peter Nap) posted ten minutes ago. She is still chuckling about it. She will probably never let me go to the Blade show to meet up with you guys now...
 
I have a pyroceram plate on my platen, been getting a pretty nice light show the last couple weeks! I've gotten used to the bite by now but it's been fun to watch my buddy Steve; he ain't used to it at all. :D If you dim the lights, the spark is a nice purple color. Kinda restores some of more nostalgic moments of my misspent youth... ;)

Maybe I'll give in and direct ground the machine. I think that's a good idea all around.
 
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