More grindie questions...

BruiseLeee

BruiseLeee

Joined
Sep 7, 2001
Messages
5,946
Using the leather belt on the grinder this afternoon, I noticed that the belt and steel create a lot of static electricity. This discarges when the blade gets close to the metal parts of the sander. Sometimes with a 1/4" arc of blue elecricity. Not too much of a deal with a big blade. You can feel a little shock. However, I tried a karda....

The smaller size of the karda builds up and releases the charge faster than the large blade. Maybe twice a second with an audible click. The discharge being in close proximity to my fingers causes some mild discomfort. The karda goes click, click, click and I go ow, ow, ow. This makes it difficult to hold the blade still. Do I need to attach a chain to the karda before grinding to stop this?

Also... What grit belt does one use to set up the initial edge?

What grit for reprofiling?

:confused:
 
1) I wouldn't get anything near the belt that could get caught in it! I think you'll be saying more than "ow, ow, ow" if something gets tangled in the machine.

2) Other than waiting for a humid day, can't make any suggestions...

Take that back, I could imagine something like a grounded "brush" like in a electric motor that would take the charge on the belt to ground by an alternate route than you, but it would have to be carefully made to eliminate the chance of entanglement.

Ask the guys on the shop forum, I've seen this discussed there before.
 
Gee Bruise...I kinda like the snap, crackle, pop part of all this. Maybe you just aren't man enough to use grindie things yet?

Seriously, I just try to make sure I ground out every so often to get rid of the charge purposely. It doesn't seem so bad when I *know* it's going to happen.

As for the grits, it depends on how much metal I'm moving...I've gone as low as 80 but generally 180 is low enough. One thing I consider is that if the blade is getting too warm too quickly, I go to a lower grit (180 to a 120) so the heat buildup is less.
 
Bruise,
I have had a similar problem at work when using one of out cabinet blasters. I ended up making a ground strap that goes from me to the machine. This helped in my situation. Hope it can help in yours. :)
 
The discharge is happening on the surface of the belt because it cannot send the extra electricity back to the body of the sander.

The safest solution is to get 2 alligator clips, put a wire between them, clip one end to the machine, and one end to the metal you're working with.

This, unfortunately, is not very practical advice....:(

I just deal with the sparks and keep my fingers back a little when I use it. Still get shocked when I grind, though.

But not on my big grinder. Because there's a large enough metal platen behind the belt - it allows the electricity to go back into the grinder and not into me.

Electricity follows the path of least resistance.




By the way, those anti-static wrist bands that Radio Shack sells are to protect your work, not you. If it happens that you are carrying too large of a charge, it will dissipate through the band instead of the board. But should you recieve an electric charge from the board, it will go right through ya.



Another thing I do now is wear thin molded-latex gloves. See a thread I posted here a while back about it.
 
I've heard you should always put each foot in a separate bucket of salt water, and hang a 50W incandescent bulb around your neck.

That or it was never do that. Always or never, I forget which.
 
Have you tried a stainless steel mixing bowl worn like a helmet with an adjustable chin strap. Try the gallon size from Walmart. Not sure if it will help, but you'll look a lot more knowledgable and cooler than in a tin-foil cap.
 
:eek: :eek: :eek:

Sooooo, NOW we find out that the Belt-Grinder-Brigade has been self-dosing electro-convulsive therapy to themselves all along!!!!

Happy little bunch, aren't they, Sparky?

Probably grill cheese sandwiches in the aluminium wrappers while they zap-zap-zap away at themselves.


'Splains quite a bit, yes sireee ;)




Kis
We have so much.
 
What most of you dont know is that Bruise is a Weylan-Yutani model 605 "synthetic person."
His frame is a highly conductive titanium-copper alloy and the sparks are not coming from the grinder, they're coming from Bruise himself.
Bruise, if you must use that machine, please put on your Weylan-Yutani 941-0006345-A-241 20045 S.P.-Issued leather gloves to protect the machinery from your operating voltage.
 
Daniel Koster said:
By the way, those anti-static wrist bands that Radio Shack sells are to protect your work, not you. If it happens that you are carrying too large of a charge, it will dissipate through the band instead of the board. But should you recieve an electric charge from the board, it will go right through ya.
Click to expand...

Dan,
The wrist straps have a 1 megohm resistor in them. Would that prevent dangerous current from killing you if it became connected to a live wire? I always thought that was the reason for having it. If Bruise wore one and connected it to the metal of the grinder, would that help? Or would it help to take a solid copper wire, attach it to the metal frame, and let it rub against the leather belt?

Steve
 
I'm partial to the rack.

Also it temporarily corrects the some of the symptoms of osteoperosis.

Theoretically, I think the grounding strap would work. However having something on the wrist whilst using the grinder would be kinda iffy. Perhaps if it were on the ankle...

Stainless steel mixing bowls on my head make me feel like a WW2 war hero. I only use em' on special occasions. I should start a culinary WW2 re-enactors guild.
 
ferguson said:
The wrist straps have a 1 megohm resistor in them. (1) Would that prevent dangerous current from killing you if it became connected to a live wire? I always thought that was the reason for having it. (2) If Bruise wore one and connected it to the metal of the grinder, would that help? (3) Or would it help to take a solid copper wire, attach it to the metal frame, and let it rub against the leather belt?
Click to expand...
Answer to (1)

Are they covered in a insulating material? (not intentionally being a smart-alec)

The strap is to protect the work, not you. In other words, if your board suddenly becomes live with current, it's going to dissipate in the coiled strap not you. The other purpose of the strap, is to keep you from discharging your extra electric current into the board.


Answer to (2)

Think of it this way:

You have an object in front of you that is "live"(*). You attach the wrist strap to it and put it around your wrist. Fine. You don't get shocked. But you still can't touch the object. Once you do, the current will follow the path of least resistance and you, being filled with lots of fluids, will glow like a lightbulb (since you are now the path of least resistance.)

So, having learned your lesson, and having combed what remains of your hair back down onto your head, you throw away the wrist strap, take a healthy-sized wire and hook it from the "live" object to a large piece of metal (hereafter called "ground"). :D Still a bit shaken from the previous experiment, you reach your finger out and quickly touch the "live" object. Amazingly, nothing happens. You touch it all you want....still nothing happens. Why no discharge? Because despite all the coffee you had before the experiment, your boney, rubbery-skinned hand is no match for solid metal and it is no longer the path of least resistance.



(*) in this particular story, "live" equates to a significant difference in "charge", that is, electron count. The "live" object could be carrying too many electrons, and you could be short a few yourself....:p.....when the two come together, current flows via your finger and...zap! This is static electricity. Different story with applied current (like in a light socket).....but still equally illuminating.....:footinmou



I've done metal grining in a shorts and a t-shirt, wearing wet shoes on a one-inch thick layer of ice (don't ask why)....from all outward appearances, I should have taken quite a zapping, but since my machine is properly grounded, any "buildup" in positive electron energy is dissipated to the ground, instead of me. :D


The most practical way to solve your static problem is going to be this:

Take a metal wire, strip the ends off a good inch or so. Tape it to the back of your platen (or anywhere on the machine close to where you work) and run the end down to a concrete pad, a metal column, a railing, a tool stand, etc. - anything big, heavy, metal-ly.....

If you get any extra discharge, it will follow that path instead of you.


Answer to (3)

Almost got it..!!

You don't want to hook it back to the machine permanently because while the heavy metal of the sander can certainly absorb occasional outbursts of electrons (much like Twisted Sister) - it will still buildup and suddenly discharge sending your knife into the belt, or worse your hand. (wonder how I know these things....?:D)




Answer to (4)

:p :p :p


You can also spray the back of your belts with WD40. And it will supposedly cut down on the static. There's something else some guys do in ShopTalk - another chemical to spray on the backs of belts...can't remember though....but it's not paint.....


:footinmou
 
Bruise just dress in black leather chaps and vest, and then you can start charging to shock people :eek: :rolleyes: :p :barf:
 
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