Grinder static!!!

F

FloWolF

Joined
Sep 15, 2017
Messages
70
So, is it just me that gets huge static shocks whilst grinding handles on hot dry days? I never noticed it before this summer, but now it keeps on getting me big time and my nerves are wrecked! NOT a good state to be in when at the grinder I'm sure you'll agree...

Anyway, anyone else suffer this problem and has found a solution? Do I need to go as far as a conductive wrist strap and discharge cord to the grinder body?..

Just to add - it's me that is collecting the charge, the properly grounded grinder is what I'm discharging to.

Cheers folks! I'm off for a long walk now to get the rest of these jitters out of me - it's already cost me 2 rally fine blade edges!

Shaun/FloWolF
 
No guarantees, but maybe change shoes ? Google "Electrostatic Dissipative Work Shoes".
 
This is a regular topic. You can use the search engine to read hundreds of replies.

The short answer is to use some way to dissipate the static.

The cause is dry air, usually cold dry air, but dry is the important wrd. This allows static to build up in you as the grinder sucks electrons off the knife that you are holding. When you touch or come close to a grounded object the difference in charge transfers all at one as a mini-lightning bolt.

There are all sorts of things like ground straps and shoe strips, but the easiest for a knife shop is to spray the back of the belt with "Static Guard Laundry Spray". Just a quick blast when you put the belt on will do it. You may not need to do it again even with another belt for a while.
 
J. Hoffman said:
I have one on each grinder. Works great.
Click to expand...
That's the sort of idea I was hoping for. I have a bit of electronics background and couldn't quite see past the anti-discharge gear sometimes used during circuit assembly. Your suggestion fits the bill, cheers!
 
I ordered a glass platen when I started making knives and after ordering it / before it arrived I read here that a glass platen causes static shocks ( and I bet I hate getting shocked as much as you, lol )so when it came in I tossed it in a box and never used it. Thats been 10 years ago. Instead ,based on advise from this forum, I use a hardened steel platen and have never been shocked.
 
Stacy E. Apelt - Bladesmith said:
This is a regular topic. You can use the search engine to read hundreds of replies.

The short answer is to use some way to dissipate the static.

The cause is dry air, usually cold dry air, but dry is the important wrd. This allows static to build up in you as the grinder sucks electrons off the knife that you are holding. When you touch or come close to a grounded object the difference in charge transfers all at one as a mini-lightning bolt.

There are all sorts of things like ground straps and shoe strips, but the easiest for a knife shop is to spray the back of the belt with "Static Guard Laundry Spray". Just a quick blast when you put the belt on will do it. You may not need to do it again even with another belt for a while.
Click to expand...

Thanks Stacy, I'd have likely thought of using the search function myself if I hadn't been in shock. Heh.

I'll take a look over here for that spray or evuiv. thanks.

I thought I knew what was happening was happening with regards to the generation of the charge as I'm into such things and I know when you rend many hard materials electrons are released as the molecules come apart, I just couldn't figure out why it had never got me before so to speak, and why I'd never come across it in forum chat and such.

However I don't now believe that is where the major portion of the charge was being generated - it seems the missing piece of the puzzle is my relatively recently added glass platen, the relevant fact of it being there escaped me completely in the moment (I'd been zapped several times, and then in a rattled state state I managed to grind little chunks out of the finished edges of 2 almost completed knives, my adrenaline had gone through the roof and I was blazing mad to say the least) - that it was not only an insulator for any charge that section of the belt was carrying, but it is also a major point of static generation as the belt fabric slides across the surface, much like some of the old static experimenters did with a glass rod and a soft duster - it is in essence just a Van De Graaff generator, and me with the knife in hand am acting as the collector.

Still the solution should be the same regardless - I'll look out for the spray, and J. Hoffman's chain suggestion too. Cheers!
 
You can find the static guard in the grocery with the laundry soaps and dryer sheets.

It is not free electrons coming from molecules being torn apart.
As one insulating or insulated object moves across another one will capture electrons from the other, making one more positive and one more negative. Now, the earth can take a lot of loss and never show any change in charge, but a small, insulated object can amass a large charge differential. That object is called the storage well. Rub a balloon with a piece of wool and it will cling to the wall or discharge a tiny spark to a doorknob - the balloon is the well. Run a rubber belt across a phenolic wheel in a Van De Graaff generator and it will build up thousands of volts of static energy. The dome at the top is the well. Allow clouds to stream across a layer of dry air and billions of volts build up until they jump to ground as lightning. The cloud is the well. The grinder is a very simple Van de Graaff generator, especially with a glass platen. You are the storage well. In all cases, the discharge is eventually into the earth. If you allow the charge to bleed off continuously, it never builds up to the point it makes a large potential, thus no sparks or shocks.
 
Stacy E. Apelt - Bladesmith said:
You can find the static guard in the grocery with the laundry soaps and dryer sheets.

It is not free electrons coming from molecules being torn apart.
As one insulating or insulated object moves across another one will capture electrons from the other, making one more positive and one more negative. Now, the earth can take a lot of loss and never show any change in charge, but a small, insulated object can amass a large charge differential. That object is called the storage well. Rub a balloon with a piece of wool and it will cling to the wall or discharge a tiny spark to a doorknob - the balloon is the well. Run a rubber belt across a phenolic wheel in a Van De Graaff generator and it will build up thousands of volts of static energy. The dome at the top is the well. Allow clouds to stream across a layer of dry air and billions of volts build up until they jump to ground as lightning. The cloud is the well. The grinder is a very simple Van de Graaff generator, especially with a glass platen. You are the storage well. In all cases, the discharge is eventually into the earth. If you allow the charge to bleed off continuously, it never builds up to the point it makes a large potential, thus no sparks or shocks.
Click to expand...
Not posting this from an argumentative standpoint, just to let you know where I was coming from - when covalent/electron-sharing bonds are broken, the electrons that were being shared return to either parted body - when they are shared evenly between the two they call it homolysis/homolytic and no extternal static charge is created, but when the breakage leaves an uneven charge it's referred to as heterolysis/heterolytic, and in this latter case the charge gets pulled and builds on whatever is already predisposed to that charge due to environmental and other factors, and this happens with quite a number of such molecules, and some molecules will behave either way depending on outside factors. -

- My first introduction to this phenomenon was decades ago whilst working at a plastic injection molding department (I've worked in a couple situations for that company with high risk of large static discharges), and the plastic regrinding machine generated a ton of static right as it sheared the plastics. If you opened the door and took out the bucket and ran the thoroughly pre-discharged machine up, then chucked a chunk of plastic in, as soon as the bits are past the blades they start to float and attach to the machine walls.

At first I'd wondered in my stunned state if a similar thing was happening with the polymer stabilised wooden handles on the 60 grit belt. It took a while to click but as my head cleared from the adrenaline fog, I began to see the real picture.

It's been a long time since I studies the sciences and paid attention, so I don't always recall the commonly used terminology, but I can usually make things clear enough so people understand what it is I'm referring to.

Cheers again, and thanks for helping keep such an invaluable resource all that it is,

Shaun/FloWolF
 
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