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Power tools and water

Does what it says on the tin
MyNameIsUrl
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Power tools and water

#389838

Postby MyNameIsUrl » February 25th, 2021, 8:31 am

I have a mains-powered Dremel which I’m about to use to drill some small holes in pieces of glass. The usual technique is to hold the glass on a piece of wood in a shallow plastic tray of water, so that the glass is just a few mm below the surface.

Does this pose significant danger of electric shock? Although I use power drills, pressure washers, etc without feeling in great danger, something about having my fingers in water is worrying. Would it make the risk greater if the plastic tray was on a metal draining board next to a sink and taps?

Urbandreamer
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Re: Power tools and water

#389847

Postby Urbandreamer » February 25th, 2021, 9:22 am

The key danger is mains electricity finding a path through the heart.

Water is only the issue in that it allows a better contact between your skin and the electricity supply. Now plumbing. ARGH!
That is a HUGE risk. The sinc and drainer should be connected to one side of the electricity supply (earth), by regulation. DON'T work near the sinc.

Now if you are standing on a rubber mat or wearing boots/shoes with a synthetic sole, it will be more difficult for the electricity to travel through your legs to earth.
The plastic tray will ensure that electrcity can't pass through it.

Assuming that the dremel is faulty and either the handle or tool becomes electrified, either the hand holding it or the hand supporting the glass will be connected to the mains. But where will the electricity flow to?

You can improve on the safety. Wear new rubber gloves. That way your hands can't contact the dremel directly or via the water and tool. You could use distilled or deionised (available from a garage) water. They conduct electricity significantly worse than tap water. Distilled would be better, but harder to obtain. I'd simply use new kitchen gloves.

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Re: Power tools and water

#389854

Postby quelquod » February 25th, 2021, 9:50 am

Unless you’re system is already equipped with an RCD use a plug or adapter with a standalone RCD. Provided you test it from time to time as you should you will be perfectly safe. Trying to cobble together a variety of insulating methods is all very well and you’d have to be really unlucky to get a fatal shock from most recent pieces of undamaged equipment but a tested RCD is the way to go.

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Re: Power tools and water

#389860

Postby jfgw » February 25th, 2021, 10:02 am

It is the sort of thing I would do without worrying. How big are the holes? What type of bit are you using?

Do you have an rcd? This should trip before a shock becomes fatal. They are not intended to allow you to take extra risks though.

Can you avoid using the tray of water? Either keep dipping the drill bit in water or use plasticene, putty, Plumber's Mait, whatever to hold a small pool of water around the hole.

Distilled or deionised water will be conductive if it gets contaminated by sweat, dirt, etc.

How powerful is the Dremmel? You might be able to rig something using an isolated shaver socket. You would need to check the power though. Is this a one-off or an ongoing thing?

You could use a different coolant. Water has advantages though.


Julian F. G. W.

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Re: Power tools and water

#389875

Postby Mike4 » February 25th, 2021, 10:32 am

Never mind all the measured suggested above, I would suggest using a decent quality battery powered cordless drill. They are better than mains drills these days.

Edit to add:
P.S. don't use it on "hammer' setting :lol: :lol: :lol:

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Re: Power tools and water

#389913

Postby Mike4 » February 25th, 2021, 11:29 am

Mike4 wrote:Never mind all the measured suggested above, I would suggest using a decent quality battery powered cordless drill. They are better than mains drills these days.

Edit to add:
P.S. don't use it on "hammer' setting :lol: :lol: :lol:



Re-reading my post, I forgot to mke my main point which seemed so obvious to me I forgot to spell it out!

With an 18v battery drill there is virtually no chance of electrocution, whether or not you have one hand in the water.

Cue a string of posts citing people electrocuted by their 18v power tools!

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Re: Power tools and water

#390347

Postby csearle » February 26th, 2021, 5:51 pm

I think you'd have to be bloody unlucky to get a lethal (or any) shock. Keep all but the tip of the Dremel dry (obviously). You could wear a rubber glove on the "wet" hand if you really felt like it.

Providing the thing containing the water is non-conducting (e.g. a plastic tray) then you would be at no more risk than if you were just standing there holding it in the air I reckon because if the Dremel is:

  • class 1 equipment (Earthed) and a fault to Earth occurred within it and the MCB/RCD failed to trip, or
  • class 2 equipment (double-insulated) and both sets of insulation simultaneously failed,

then the water would not be a path to Earth anyway, so no current would be passing through the tissue of your heart.

Chris
PS Might be different if a fault occurred with the elbow of your "wet" arm is resting on a metal earthed bench, so watch out for that! :)

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Re: Power tools and water

#390366

Postby Redmires » February 26th, 2021, 7:15 pm

It's perfectly safe if you use Q20, as shown here*

https://www.youtube.com/watch?v=qtiyYBo4_38

I was searching for the Tomorrows World clip from the 70's but this is a modern equivalent.

* Don't try this at home kiddies

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Re: Power tools and water

#390709

Postby MyNameIsUrl » February 27th, 2021, 7:48 pm

Thanks for all the replies. Sounds like getting a shock is pretty unlikely, but to be on the safe side I've bought a 3.5v cordless Dremel. It's actually my wife using it, so I don't want to take any chances.

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Re: Power tools and water

#390714

Postby Mike88 » February 27th, 2021, 8:02 pm

Drilling holes in glass usually ends badly. After breaking several panes there are two golden rules. Use a glass bit and use the drill on the slowest speed and don't apply pressure to the glass; otherwise it will crack. It will take a long time to drill a hole but patience is essential.

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Re: Power tools and water

#390767

Postby servodude » February 28th, 2021, 3:09 am

Mike88 wrote: there are two golden rules. Use a glass bit and use the drill on the slowest speed and don't apply pressure to the glass;


I'd add a fourth to those two with "make sure it's not tempered glass"

But the spear tipped carbide bits are the tool to start with

- sd

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Re: Power tools and water

#390788

Postby Mike4 » February 28th, 2021, 7:36 am

Mike88 wrote:Drilling holes in glass usually ends badly.


This can't be universally true as glass merchants routinely drill holes in glass for not very much money. I'm sure they don't need multiple attempts after repeatedly breaking the workpiece!

So obliquely, the OP could perhaps get it done at the local glass merchant, if their attempts end badly as you suggest.


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