Electric shock from belt sanders


Apr 28, 1999
I didn't think of the tool rest and the sparks going to that! I will get some static guard and a brass brush and do both. Really frustrating when you are grinding away and it just powers down and you get shocked!
Nov 11, 2021
I keep getting electric shocks when I touch metal on both of my belt sanders, including when I turn them off. It's a bit painful but mostly it makes me jump when I am trying to be careful and precise resulting in mistakes on my projects.

Does anyone know what causes this? And how to stop it? Grounding problem with the electrical outlet? Static build up?

Solve with rubber shoes? I'm at a loss.
Static build up wouldn’t cause that, especially on a grounded tool. You most likely have a loose wire inside, a grounding issue, or something could be arcing. I’d unplug it and open it up and inspect

Stacy E. Apelt - Bladesmith

ilmarinen - MODERATOR
Knifemaker / Craftsman / Service Provider
Aug 20, 2004
Nope, Pheonix, This issue is caused by the moving parts stealing electrons from an insulated objects. The wheels and belts are a simple electrostatic generator if the air is dry.
they steal electrons from you. This is made worse if you are standing on a rubber floor mat or dry concrete with rubber soled shoes. Eventually the potential difference will become great enough for the electrons to jump the gap and rectify the imbalance. Grounding the collector (you) or creating a better discharge path ( Static spray or a brass discharge brush) will pretty much eliminate it.

BTW, sweaty socks and leather shore will also help solve the problem if the floor is conductive enough. This helps continually discharge the static so it does not build a high charge.
Today, they make ESD shoes - ElectroStatic Dissipative shoes to solve the issue.

Fun Story:
In the pre-LED/LCD screens and LED lighting days I used to do electronics in the Blue Room - the static build up was severe to say the least.
Blue room - Air Traffic Control Center with radar screens. All the lights are blue so your eyes stay dilated to read the dim green/yellow screens on the scopes. The screens were sweep analog, so the controllers had to use grease pencils and put dots and lines on the screens to track the planes. You had to stare at the screens almost constantly to keep track of which plane you were guiding.
The rooms are chilled to around 60 degrees to keep the old analog CRT equipment cool. While most of the main decoding equipment was in the Radar Room nearby and was transistorized, the power supplies in the scopes to drive the screens and other circuits created a lot of heat. The air was dehumidified to a crazy low relative humidity to prevent other electronic issues. The air is heavily filtered to eliminate all dust. The carpets were nylon. This combo is a welcome mat for static electricity. People in normal shoes who came in got shocked every time they moved and touched something.
The fellows who tended the scopes all had grounding wrist straps and shoe tabs that trailed behind them. Even then, getting up and walking across the room to the door could create an inch long spark. Also, some of the guys just didn't care and expected the shocks. They would always lay a bare arm on the scope to stay grounded and walk around the room trailing a hand on the equipment. Someone discovered that spraying your pants cuffs, socks, and shoes with Static Guard would also eliminate most of the problem.
I used to demonstrate to people unfamiliar with the issue just how bad the static was by holding a fluorescent light tube in my hands and shuffling my feet (while ungrounded). The tube would glow eerily. Then I would reach it out toward a metal object and it would flash like a flash bulb as the static discharged. Obviously, I did this when it wasn't busy and with the controllers on the scopes alerted to close their eyes momentarily. Today, none of this is an issue anymore with computer terminals and different lighting.
When I installed the TPX-42 digital radar units with continuous digital images on the screens the guys thought it was Star Wars. You could program your station to follow a certain plane and do all sorts of other identification inputs for other planes. Each plane could be a different geometric shape symbol. The screen gave you all the planes in the air as the symbols you programmed and listed their altitude and bearings. It even had an alarm for any planes that were too close or on an intersecting flight path. The neatest things was a brand new code 7777 - Highjack. If the plane pilot flipped an innocuous switch, the code showed on the ATC screen and was surrounded buy a series of alarm triangles. All hell broke loose in the Blue Room when that happened. More times than the Govt. would like to admit, this happened accidentally by a pilot not paying attention as he switched on the cockpit switches, or when a maintenance worker in a plane on the ground accidentally hit the switch.
Last edited:
Feb 12, 2015
Agree with Stacy, this is most likely a static issue. However, you should probably use a gfci outlet to power your grinder. That will eliminate the possible wiring hazard.