Weird, kind of freaky... Or is my lathe trying to kill me?

[Sam Fleisher]

I had a walnut bowl/platter that I was working on and was applying a wax finish because I hadn't for a while. Was using EEE paste and was wiping it off with my right hand with my left hand resting on the headstock.

First time I thought I'd hit a metal splinter with my left index finger so I got to looking and there was a minuscule spot of paint that had been knocked off somehow and when my finger touched it I was getting shocked. Shut everything down and started looking at all the wires and the plugs and the light sitting on top. Nothing. Called a buddy who is retired from ameren (local power company) and he said sounded like static electricity generated by the spinning wood to him since I wasn't blowing a breaker or anything and my outlet was installed by a licensed electrician.

And sure enough the only way I was able to duplicate it was by having the bowl spinning with dry wax on it and touching it with my right hand and then tapping my left fingers on that little spot of missing paint. If I didn't touch the bowl or the wax was wet, no shock anywhere else. And after he said that about static electricity I thought yeah it did feel kind of like that. Pretty strong though but it wasn't like what the 220 would have done.

Probably would have just went to ground except I had my OSHA approved crocs on.........

Is this pretty common or should I call B.s. and keep looking?

 

[Emiliano Achaval]

I’m looking forward to seeing what some our guys have to say. We have some experts here that will be able to shed a light on this. I have to say, I have never heard something like this.

 

[Sam Fleisher]

I’m looking forward to seeing what some our guys have to say. We have some experts here that will be able to shed a light on this. I have to say, I have never heard something like this.

I did find a post from 2007 I think where they were talking about similar and about dust collectors. The guy I called was a retired Master electrician. As opposed to a journeyman I guess.

 

[Richard Coers]

Use a multimeter and check voltage at that point to an earth ground to measure if there is any current there before you turn it on. Getting the shock with the platter spinning could be because the motor was running?

 

[Brent@TurnRobust]

Not sure if it's related, but static shocks when belt sanding metal parts are very common and hard to mitigate without grounding the operator to to the equipment. Google it, lots of references. We just learn to stay at least an inch or so away from the belt sander. Seems the sparks won't bridge a gap bigger than that.

 

[Mike Johnson]

VFD's can produce an induced voltage on a motor rotor shaft which can cause a shock, the voltage usually builds up and
arcs across the motor bearings causing bearing failure over time. When this problem occurs, they usually install grounding brushes
on the motor shaft to safely move the induced voltage to ground away from the bearing path. One hand on the bowl and one hand on the
grounded metal surface would create a potential for shock.

If you are using a dry cloth to polish the finish on the bowl you could also be creating a static charge on the bowl while it
is turning on the lathe, touching a grounded metal surface would provide a path to ground creating the shock.

 

[Sam Fleisher]

If you are using a dry cloth to polish the finish on the bowl you could also be creating a static charge on the bowl while it
is turning on the lathe, touching a grounded metal surface would provide a path to ground creating the shock.

That's similar to what my buddy said.
I was using a paper towel, one of those really soft viva ones and I tried lots of combos to re-create a shock while I was talking to him on the phone and it did only do it when the wax was dry with the bowl spinning. I had to be touching the bowl with one hand and then the other was on the head stock on that first spot or the screws holding the control panel on. I didn't think to try touching anywhere else while touching the bowl because it hadn't occurred to me yet. Touching anywhere else, motor running without my hand on the bowl didn't shock me. Touched the motor, lathe bed even the chuck. nothing. It just seemed bizarre after he said that because to me wood isn't a conductor.
First thing I was thinking was something was shorting out in the headstock but the operation wasn't affected at all.

 

[stu senator]

You are following in the footsteps of Ben Franklin, see:

https://inspectapedia.com/lightning/Benjamin_Franklin_and_Lightning_Rods.pdf

He also did a number of experiments in static electricity. Plenty of references on the web.

Stu

 

[Dave Landers]

In my previous shop, I wore crocks (diversion - the shop was downstairs thus connected to the house and I brought in less shavings with bare feet vs socks - put the crocks on as I went in/out - new shop will be detached and I'll come up with something else because walking barefoot thru the snow is not on my todo list). Anyway, crocks (and any rubber soled shoe) will insulate well and I'd get static shocks when buffing.
The solution is grounding yourself - for you since you're already resting your hand on the headstock, just hold your finger (etc) on bare metal there. I would slip my foot out of the crock and touch the foot of the lathe. Back when I used to work with electronics, we'd have a wrist strap (conductive paper/cloth/something grounded to the table to avoid zapping the circuitry. It's the air-gap that makes the spark (jumps the gap and you feel the shock) - give it a place to go without making a spark and it's more comfortable.

 

[Darryl Fective]

I wonder if your lathe is not grounded. I would think if unplug the lathe, you should have continuity between your ground pin on the plug and the bare metal spot on the lathe. (and motor, VFD, etc.) If not, you need to find out why.

 

[Dave Landers]

So in regards to the grounding of the lathe - I expect the lathe is grounded and what’s happening is that Sam is not so he’s building up a charge (by applying the finish). When he’s charged up enough the static electricity will discharge across the gap between his finger and the ground (that is, the lathe).
If he gets grounded then the charge will dissipate and not build up.

 

[Richard Coers]

How do you build up static applying a layer of finish on wood? There a continual layer between the wood (insulator) and the cotton cloth ball (another insulator). In my experience a static discharge on my hand or finger is an instant pop with pain. NOT like a metal splinter went in my finger.

 

[Darryl Fective]

So in regards to the grounding of the lathe - I expect the lathe is grounded and what’s happening is that Sam is not so he’s building up a charge (by applying the finish). When he’s charged up enough the static electricity will discharge across the gap between his finger and the ground (that is, the lathe).
If he gets grounded then the charge will dissipate and not build woodturning.

So what you're saying is that because it's never happened to me, we can assume I just feel more grounded in my turning?
.
I like your answer way better than mine.

 

[Lou Jacobs]

How do you build up static applying a layer of finish on wood?

I assume (I know, dangerous, as this is just an uneducated guess) the same way you charge a balloon by rubbing it on your shirt or sweater and having it stick to the wall.

 

[Daniel Henry]

I assume (I know, dangerous, as this is just an uneducated guess) the same way you charge a balloon by rubbing it on your shirt or sweater and having it stick to the wall.

Or the same way you build a static charge by rubbing your leather soled shoes on certain types of carpet.

 

[Dave Landers]

I assume (I know, dangerous, as this is just an uneducated guess) the same way you charge a balloon by rubbing it on your shirt or sweater and having it stick to the wall.

Yep. Or like a glass rod (insulator) rubbed on a cat (which is similar, electrically, to me or Sam).

Triboelectric effect - Wikipedia

en.wikipedia.org

 

[Marc Banka]

If the feeling of electricity is constant, that you can feel the 60 cycle vibration, you have a grounding problem. If it’s a single discharge, that would be a static thing.
Are you having dry weather in illinois?
I suspect that it’s you discharging to your machine, not the other way around.
The test would be to repeat your sanding, but instead of touching the lathe, touch something else that you know is grounded.

 

[Gabriel Hoff]

This did happen to me once when buffing, I could feel little sparks or shocks. Was weird but it won't kill you

 

[Mike Novak]

I installed a harbor freight motor on my bandsaw. After I did, I was getting shocks occasionally. Felt like static, but it was happening too often. Double and triple checked everything and could not find a problem. I couldn’t get a reading on a multimeter either. Turned out to be a problem with the motor. They swapped it for a new one, I installed it and no more problems.

I confirmed it was the motor by taking it off the machine and ran it clamped to a bench. Still got shocks.

I’d try touching the spindle when doing other things. If it only shocks when polishing, it’s static. Not likely to build up static while cutting.

 

[Mike Johnson]

As I mentioned in my post above, anyone using a VFD on a 3-phase motor you have the potential for induced shaft voltages on your motor.
This is a major problem in the commercial and industrial world, in some instances the arcing through the bearings can create arcing pits in
the bearing race over time and destroy the bearings if the induced shaft voltages are constant. There have been a number of white pages
published in the IEEE and NEC standards over the years. Not all VFD's or motors will induce this phenomenon, but many do, One facility I
worked at had about 300 VFDs on the site, we had to install grounding brush systems on about 25% of the motors to reduce motor and
bearing issues on the bigger more expensive motors and measured the intensity of the induced shaft voltages on the others to determine
the cost benefit of installing shaft grounding brushes or replacing the motors when they failed.