ShopTalk Forums | Aircooled VW Tech & Restoration Help

I keep thinking about my chop top bug and have stock tempered glass, but no extra to experiment on.

Do you think I could put a sheet of metal under the glass and then cut the glass with the plasma?

The flame should be hot enough, I just wonder if anyone has tried it.

Kevin

I have no on plasma (too hot I would think), but I do know that a water-jet will do it.

John
Aircooled.Net Inc.

I thought a plasma cutter worked on an electric arc and air pressure to blow the burnt metal away. Kinda like an arc welder with air and high amps to actually burn the metal . Can't arc it through glass. Bill

i think thats what he was getting at with the sheet metal on the back side of the glass

I believe the heat will cause expansion and shatter the glass.

I predict you will explode the glass too.

If you want glass made, take a stock piece of glass and hold it in a stock window opening to see how it fits. Then make your template from thin sheet aluminum and get the glass cut to fit. Once its cut they will temper it for you. I just got a pair of rear windows made for $40cdn.

you can make you own useing poly-carbonate or lexan just be carefull not to scratch it up.

Only electrically conductive materials can be cut with a plasma cutter. Glass is not conductive. Sorry.

kevin @ No Dollars Racing wrote:Only electrically conductive materials can be cut with a plasma cutter. Glass is not conductive. Sorry.

thats why there would be sheet metal under it. To make the complete circuit.

I would like to try it, maybe I can find some tempered glass somewhere. for free.

Kevin

Bruce2 wrote:...Once its cut they will temper it for you...

Another option would be to have them cut from laminated safety glass (the stuff used in windshields). Cadillac started doing that long ago, both for safety and reduced noise & UV transmission.
http://computer.howstuffworks.com/question508.htm
http://www.alumaxbath.com/tech/tgp.htm

Note the trick of using polarized sunglasses to see if the glass is truly heat-treated.

I am a bit confused now, If you have glass between the tip and the metal backing plate, then you now have a non conductive unit in between, so why does it matter if you have metal under it or not if the conduction is not there to start??? Somebody let me know. I dont want to sound stupid but huh?

With my plasma as soon as I get about 1/2" ( it could be more since I have never really looked at how high above it starts) away from the metal it will start the plasma arc. Anything in the way would also get cut. It could be wood, leather, glass anything as long as I stay within the range for the plasma to keep the arc flame going. The key would be to have the metal stick beyond the glass so an arc could be started, then move it onto the glass and the arc will continue through the metal under it.

Kevin

A few times I was cutting away with my plasma cutter,then realized the ground clamp wasn't attached.It didn't seem to matter if it was connected or not.

glass is an insulator not a conductor and shouldn't let the arc reach the metal. if you started it with the metal and traveled to where the sheet of glass was, you would lose the arc. as far as the electricity was concerned the distance wouldn't be in a straight line but rather in a curved line around the glass and back to the metal. once that distance was greater than the 1/2" or so that you needed for an arc, you'd lose the arc.




at least i think.



paul

OK I cut my 1/4 window glass tonight with the plasma. I got about 1 1/2" into the glass then it shattered from the heat. I was actually surprised, I had thought while I was cutting this is way too easy.

As a note though, 1 time in the cut I went to fast, and the flame cut out since the glass did block the flame travel as it was not melted yet. As long as I went slow the glass was being melted. I used a sheet of 1/16" steel underneath to conduct the current.


Myth busted.

Kevin