Controlling static shocks on a belt grinder

Bob Ohlemann

Bob Ohlemann

Joined
Dec 5, 2013
Messages
1,180
Ok, new question. I'm waiting for USA Knife Maker to get the ceramic glass platen liners back in stock. I've read that they can produce a lot of static electricity and produce some pretty serious shocks. I've not yet built the stand for my grinder but it will be made of steel. I'm sure others out there have dealt with this situation and I'd like to avoid it entirely. I'm of the mind that I should be able to just run a ground strap from my grinder to the metal purlin behind it. My shop is all welded steel construction and is grounded. Will this work to prevent the buildup of static electricity in the grinder?

Bob
 
The shock is due to the running of the belt over the steel. It is YOU that would need to be grounded... A copper wire or something between you and the grinder body would do it. I get the shocks too, but never felt they were a real issue. Just little snaps. Some have been pretty good. Like a long blade and going back to center. POP! I used to work with a lot of PVC which can really build up a charge if you are doing anything that rubs it. Same thing...

If you keep the heel of your hand on the work platform and grind a little, you will see what I mean. No shocks. Again, the differing charge is building up on you from the grinding. I guess you could make some sort of pad to stand on that is grounded back to the grinder chassis. Again, I never found it to be a big enough of an issue to go that far with it.

Cheers.
 
I usually only have a problem with this during the winter months when the air is pretty dry here. I have found that spraying the belts with "Cling Free" or some other type of anti-static spray usually does the trick pretty well.

Kevin
 
  • Like
Reactions: HPD
Makes sense since the motor is already grounded and it is attached to the chassis of the grinder. An additional strap for the machine would be redundant. On a google search, I did see a knife maker demonstrating how he attaches a large alligator clip to the blade steel and a wire runs from the clip back to the grinder. It is apparently less of an issue in higher humidity which we usually have a good amount of here in DFW. I'm not a fan of getting shocked. My truck nails me every time I get out and go to close the door.

Bob
 
Using my jig I haven't had a problem and I guess that explains it. I am always in co tact with the grider.
I used to work for an auto dealer and when cars started coming with computers in them the mechanics had a wrist band that has a wire with a clip on it to keep them grounded.
 
Funny this should come up. At work we are aggressively trying to nail down some static electricity issues. Just in case anyone thinks they can't be serious... Trust me, they can. I didn't realize that.

Anyway, as far as the grinder goes, I get zapped regularly, but it doesn't bother me enough to do anything about it. At least not yet. Humidity is uncommonly low here. People will be marching on the state capital to raise a state of emergency for water. Hopefully the low humidity doesn't translate to more serious issues with the grinder. We'll see.
 
Last edited:
I don't think it ever occurred to me to use anti-ststic spray on the belts... neat-o.

In CO where it was always a lot dryer than here, I would keep the static cling type dryer sheets in a pocket or something. Rub down dress pants to keep em from sticking to my hairy old legs...
 
The belt rapidly moving across the roller on a dry day will remove electrons from it. This makes the grinder a small Van de Graaff generator. Your body is touching the ground, so you become a source for replacement electrons from the biggest repository around - the earth.

On the worst dry days of the winter it can get pretty bad. I have sent mini lightning bolts from my fingers to the grinder.
I made a static strap that I occasionally use. It has a 1 megohm resister in the center of a 5 foot long piece of 16 gauge stranded wire. On end has an alligator clip to attach to the grinder base and the other has a 1X4" strip of copper. I stick the copper strip in a pocket or in my waistband. This provides a path for static, but the resistor would prevent any current from passing to me if there was a ground fault in the grinder.
When I did electronics for the Govt. we regularly had to wear one of these ground straps to prevent CMOS chips from being fried by static.

Anti-static spray that women use to keep their skirts from clinging works well also. Spray the belt back and the roller areas with it. It creates a pathway for the electrons to bleed back to the rollers that they were pulled from.
 
Static electricity builds up easier when it is dry outside. The wetter the air is, the less likely you will store it up.

A humidity gage, and a grounding strap should work for you. I personally don't like the idea of wearing a grounding strap while working with electricity, like a grinder uses. But if the humidity is low enough that experience shows the zaps are too great, wear the ground strap.

Too late. sounds like bladsmth got it already... CMOS chips eh? We are looking forward to those being used as humidity sensors in my industry. :D
 
I had this issue and now use a wrist grounding strap. I get them from work as we have to be grounded to work on a lot of our communications equipment. One end is clipped to my grounded grinder frame and the other end goes around my wrist. The ones we have are safe around the grinder as the. Have a break free connection at the wrist, the grounded end and in the middle of the cord.
 
I live in a pretty damp climate so I only seem to get this when using the J flex belts.
My solution? I rest my hands on the tool rest, or maintain some contact with it with a wrist. I like Stacy's approach.
 
Why would you be getting shocked from a grinder unless it isn't properly grounded. Perhaps you need a copper ground wire running from the platen to the grounding point of your motor/VFD.

Twice a year, I rig up the drill press to drill out bricks for the forges. It involves a 2½" forstner bit, a shop vac, and a LOT of very dry firebrick dust. The last batch of bricks was around 300 and produced about 12 gallons of dust. Even on a muggy day in August, there is enough static created by the dust going through the hose that it will give a very nasty zap 2-3 times per second if your skin is within a couple inches of grounded metal. My solution was to wrap bare copper wire around the end of the hose with about 2" sticking inside the hose. The wire is about 6' long and the other end has a small magnet on it and attached to the screw holding the coverplate on an outlet. I never get shocked now.
 
Zaph,
This has nothing to do with AC current and its grounding. The grinder can be grounded properly and the same thing will happen. It has to do with electron depletion. The grinder belt carries away electrons from the rollers. This makes the assembly positive. Once the positive charge builds up to a sufficient potential, the fastest path for replacement electrons from the earth is anything that comes close enough for the air gap between them to become ionized. This is your hand usually. The spark jumps from your hand to the grinder to deliver the needed amount of electrons. FYI, lightning does the same thing. jumps from the ground to the cloud to restore the positively charged cloud to neutral. Your eye does not see the electron discharge, but it does see the super-heated plasma that forms along the path. This heats from the cloud to the ground as the current flows. Also, pointed objects are the best source for electron flow ( it concentrates there, somewhat like a fire hose nozzle makes the stream go farther)....thus the shape of lightning rods.
 
The human body is NEVER an easier path to ground than copper. Add some copper grounding to the platen or tracking(in the case of a glass platen) on your grinder and you shouldn't get shocked.

However, the thought of a wrist strap dangling around a grinder, buffer, or drill press is like long hair and an untucked shirt around a wood lathe.
 
zaph1 said:
The human body is NEVER an easier path to ground than copper. Add some copper grounding to the platen or tracking(in the case of a glass platen) on your grinder and you shouldn't get shocked.

However, the thought of a wrist strap dangling around a grinder, buffer, or drill press is like long hair and an untucked shirt around a wood lathe.
Click to expand...

NEVER is a big word.

I never feel that comfortable teathering to rotating machinery. Hell even reciprocating ones too.
 
Perhaps this only happens with glass platens- they're so great to have, I guess there had to be a down side.
There's no path for static discharge if the belt is in contact with only glass and rubber, as I see it.
Grounding to the machine by resting my hand against it works great- you could also ground to the motor frame, like Stacy says, far away from the spinny parts.
What I hate is flinching from the shock and putting a divot in an otherwise nice grind line....not that I've ever DONE that....
 
elementfe said:
Perhaps this only happens with glass platens- they're so great to have, I guess there had to be a down side.
There's no path for static discharge if the belt is in contact with only glass and rubber, as I see it.
Grounding to the machine by resting my hand against it works great- you could also ground to the motor frame, like Stacy says, far away from the spinny parts.
What I hate is flinching from the shock and putting a divot in an otherwise nice grind line....not that I've ever DONE that....
Click to expand...

You bring up an interesting point. It has definitely been noted that the shocks are far worse with a glass platen, now you mention the rubber wheels. Is it the specific combination of glass platen AND the rubber wheels above and below it? I actually have a rubber wheel on top and an aluminum wheel on the bottom. I've yet to run my machine but is it possible that the aluminum wheel could offload the static being generated by the friction between the glass platen and the belt?

Bob
 
elementfe said:
What I hate is flinching from the shock and putting a divot in an otherwise nice grind line....not that I've ever DONE that....
Click to expand...

+1

Maybe my grinder isn't properly ground. I have a steel platen and get zapped. Otoh it could be when I have the platen pushed back.

I hate grounding straps. Included in the bevy of "fixes" going on at work is a strap and grounded steel wand for touching to the problem area. Obnoxious, but it's kept me out of the ER. Can't see that severe a problem at home, but who knows.
 
zaph1 said:
The human body is NEVER an easier path to ground than copper. Add some copper grounding to the platen or tracking(in the case of a glass platen) on your grinder and you shouldn't get shocked.

However, the thought of a wrist strap dangling around a grinder, buffer, or drill press is like long hair and an untucked shirt around a wood lathe.
Click to expand...

Like I said the strap has three seperate, very weak break away points and is designed to be used around fans and machinery that is static sensitive
 
You must log in or register to reply here.
Back
Top