Why is my miter saw arcing at the dust port

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Forum topic by RichardDePetris posted 02-28-2015 06:37 PM 781 views 0 times favorited 3 replies Add to Favorites Watch
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44 posts in 1109 days

02-28-2015 06:37 PM

Topic tags/keywords: question mdf

Yesterday, I was cutting some compound miter joints on some MDF . I noticed that my Ryobi 7 1/4” miter saw was arcing between the dust port and the hose connection point. It happened somewhat regularly depending on how long it took to make the cut. The dust port appears to be made of cast aluminum. The saw only has a two prong plug and I considered taking it apart and grounding the metal part of the saw, but decided to see if it is worth doing.

Why is this happening? Is it the MDF? Should it be of serious concern? Thanks.

3 replies so far

View Matt Rogers's profile

Matt Rogers

69 posts in 1393 days

#1 posted 02-28-2015 06:48 PM

It is the static electricity. Has nothing to do with the material you are cutting, other than the fact that MDF makes more dust than anything on earth. I was blowing cellulose into my shop walls and when the static electricity built up it would jump from the hose to my body making a huge cracking sound and arcing 4-6 inches. It hurt like hell and afterwards we took to wrapping a bare copper wire around our body and running it back to a grounding screw on the blowing machine, which was grounded by the power cord.

I would not worry about it as there is such a little chance that the spark could ignite any of the material or dust. But you could just connect those parts with a quick little piece of copper to stop it happening.

I also get shocked by my dust collector hose when I drag it around to pick up all the dust on the shop floor. THe more dust I suck up, the greater the static build up in the hose.


-- Matt Rogers, and

View bigblockyeti's profile


3587 posts in 1144 days

#2 posted 02-28-2015 06:52 PM

Sounds like you could have static that’s building to a certain voltage then arcing to the nearest ground. Is the hose connection point not the same as the dust port? It could be dangerous as the dust could become the fuel and the arc the ignition under just the right circumstances. A three wire cord with grounded plug could solve the problem if you’re willing to dive into it and you can find a good surface to ground inside the motor housing. A much simpler solution would be to wrap a copper wire around both the dust port and hose connection and run them both to a know good ground.

View JoeinGa's profile


7383 posts in 1430 days

#3 posted 02-28-2015 07:43 PM

This time of year I always find myself getting reminded how fun it is to get ZAPPPED every time I touch something metal. Getting into the car is a real trick in itself. Yep, it’s Static Electricity Season !

-- Perform A Random Act Of Kindness Today ... Pay It Forward

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