Question on capability of plasma for a particular job.

Rudd · Aug 13, 2016

I have a contract to repair a bunch of steel industrial windows in a guy's pretty nice house. He doesn't want to pull the windows out and so I can take them to the shop. So, I end up cutting out the rusted sills and parts of the jambs and welding in new shapes I have fabricated.
I have been using a 4 1/2" angle grinder and a dremel for the smaller stuff, but it would be nice if I could "surgically remove" parts - say where it hits a center jamb. The grinder throws sparks and grit all over the place, it is hard to shield it enough to keep the stuff off his floors etc.
To do what I want, the plasma torch would not always be at right angles to the work, and would really need to be able to cut into a corner, think cutting a piece of angle from the inside. The nose of the torch might make it where it isn't an optimal distance from the material as well.
I'm looking at the Thermal Dynamics 15C with built in compressor so I can run it from outlets in the house and not have to drag a tank around.. eventually I will be working on the second floor of the house.
The black lines represent the 1/8" thick steel shape, assume the lines are about 1" long. The red arrow illustrate what I think may be a problem.
Before I plunk down a kilo-buck, I thought I would ask.
Thanks for any advice.

LKeithR · Aug 13, 2016

I dunno...cutting steel frames "in the wall", "in the house" sounds like a recipe for disaster to me. A plasma uses heat to cut--what happens to the sparks and slag? Can't see a grinder being much better--all it takes is one tiny spark. :eek:

Hope you've got good insurance. I would have passed on a job like that...

Sea Farmer · Aug 14, 2016

Plasma blows some pretty hot slag around, usually through to the backside of the piece you are cutting. If the frame you are cutting is still mounted on the house, doesn't that mean the slag goes inside the wall?

This seems like a bad thing. :eek:

Rudd · Aug 14, 2016

It would be a bad thing, if the house weren't solid masonry. Brick and concrete block are pretty hard to catch on fire.

Mike C. · Aug 14, 2016

I'm in the "bad idea" camp. Plasma is pretty much just an electric cutting torch. If you wouldn't try this with a cutting torch, plasma is a bad idea, too. Might be a good job for one of those reciprocating cut off tools. Not going to be as fast as the plasma, but won't set the house on fire, either.

Zonko · Aug 14, 2016

Kind of thinking about it this way: When we were redoing our big building (1940s style steel frame with light masonry to keep out wind and weather) there was a lot of cutting and later welding. You don't think about a fire hazard at all ! There is NONE in the building.
Big, empty industrial place, only steel and mineral materials. Nothing flammable in any quantity worth a single thought.

We did set the lawn on fire, though, was a super hot summer and some nasty cutting OUTSIDE the building set fire to some hay, but living in northern Europe hot and dry means hot and dry enough for a few square foot to burn before it put itself out......

So, basically. In theory...yeah...sure....fire away.

In reality the stuff around you should concern you. The building isn't gonna catch on fire. Other stuff might. His personal belongings, the floor, the garden, stuff, junk, crap, things.....
Plasma slag on a nice hardwood floor would be infinitely worse than a few sparks and some grit you can vacuum up after waiting for a moment....

That said, i perfectly understand your pain. I had some real nasty construction work done at home (landlord paid for it, no say in it......) in 2014 and 15.....the dust is a bitch.....

Rudd · Aug 14, 2016

So I guess nobody has any idea if the plasma cutter will do what I ask of it.
And yes, I've considered dragging my little plumber's torch over there, but I need the clean cut a plasma rig gives.
reciprocating saw won't do it because there is not any room for the blade to reciprocate into.

fireman1 · Aug 14, 2016

Try Renting one and give it a try. My local gas supplier/welding shop rents them. Have a bucket of water/extinguisher around and some welding blankets and let it rip. I have used other plasma cutters (external air supply) and they work well, I would try it.

adama · Aug 14, 2016

I would say my hyper-therm 30xp probaly would do it, all depends on how hard it is to get to though, will easily take a leg off small angle in preping joints if thats the kinda stuff your trying to do? but it will do corners and stuff a 4 1/2" grinder won't.

Fumes and sparks are probably worse than a grinder though, hot slags got a lot more mass than hot sparks! Old paint will make a lot more smoke than grinding, i cut up a fair bit of old painted steel parts i have to modify with it and the plasma really dislikes thick old paint, anything much more than a typical coat and its a struggle stops the cut, deflects the plasma jet, melts to the sheild etc. Thick years of gloss + rust + old puttys going to be horrible.

Can't imagine having to try and do this in place, over here i have rebuilt more than a few metal frame windows including some seriously old ones, nothing beats starting with a good grit blast, repairs and a trip to the galvanises prior to repaint install and glaze. Kinda hard to see how your going to do much better than a patch job with em in situate. Way easier to remove, plywood up the hole and reinstall a fortnight later!

Rudd · Aug 14, 2016

Thanks Adama.. that sheds some light. The next window up is only about 3' wide x 5' tall, removal might be an option. The last one was maybe 8' wide x 5' tall.

Mike C. · Aug 14, 2016

Not a Sawzall, this; oscillates, not reciprocates...

Shop DEWALT 29-Piece 3-Amp Oscillating Tool Kit at Lowes.com

DDoug · Aug 15, 2016

Rudd said:
So I guess nobody has any idea if the plasma cutter will do what I ask of it.
And yes, I've considered dragging my little plumber's torch over there, but I need the clean cut a plasma rig gives.
reciprocating saw won't do it because there is not any room for the blade to reciprocate into.

I would take some of the scrap pieces you have from prior work, and mock it up in the shop,
to see nozzle access, cut quality etc.

cyanidekid · Aug 15, 2016

blowback, LEAD WARNING!!

the thing to remember with plasma is that it is not going to be sending the slag THROUGH the cut at all times. when starting a cut, when hitting rust, old paint or an inside corner, or especially all three, it WILL be blowing the slag back at you and all around the room as well. this is especially so if it is a small self contained unit (that will limit the total energy of the slag product, vs a bigger 220 unit, but it still will be much higher than the grinder).

WARNING!! plasma will vaporize lead paint, worse for you, and possibly contaminating the surfaces inside the house.

I don't quite understand why you can't use a recip saw? stay away from the little oscillating tool, be there all day, and two blades per cut also.

the plasma will require frequent swapping out of "front end parts", electrode and cap, especially when cutting dirty, rusty or painted stuff, and that gets expensive really fast.

battery powered band saw is my choice

adama · Aug 15, 2016

^ not if its a hypertherm it won't i have done all sorts of horrible shit with mine and it just keeps going, yeah cheap plasmas may eat consumables, but please don't assume they all will because they don't!

cyanidekid · Aug 15, 2016

well, both my TD drag-gun and my Lincoln 55 had a good appetite, maybe hypertherm is better?

DDoug · Aug 15, 2016

cyanidekid said:
well, both my TD drag-gun and my Lincoln 55 had a good appetite, maybe hypertherm is better?

Warning !!

Maybe your doing it wrong eh ?

adama · Aug 15, 2016

Honestly i have used up 2 sets of consumables in total on mine, both of thoes could be stretched longer - are in reserve for nasty jobs. hypertherm reckon about 2hrs of cut time, but give or take a fair bit on that. Whilst 2 hours is praphs overoptimistic, its proably a good bet im over a hour on both of the ones i have used up. Thats a lot of cut time and i have been gouging with it a bit too which is not really what this tiny plasma is made for, but it removes weld almost as nicely as i can weld :-) All of that cut times not running any filtering over a std self draining regulator.

Rudd · Aug 15, 2016

I think adama has convinced me that I need to convince the Owner to let me pull the window and do it n the shop. Cyanide's comment above about blowback on inside corners/rust/paint makes think the plasma could do the job, this and adama's comments on the smoke etc make me think it is maybe not a good idea for site use even if there is little to no fire risk. I think all I have to do is say "lead paint" and it will be a done deal.
I used a plasma cutter a little bit many years ago in a shop. I remembered the nice clean cut, but did not remember the hunks-o-slag on the floor below, and honestly did not know about the behavior of the plasma when trying to go through rust and paint. When I used the plasma it was on nice clean freshly purchased sheet.
thanks all

PlasmaOnTheBrain · Aug 15, 2016

Plasma can give you a real clean cut, IF your in optimal conditions...
In less than optimal conditions it can blow slag and sparks all over the place, and give you a cut that looks like it was chewed off with a rat.
Oh and the slag from plasma (or oxyfuel) is more than hot enough to mess up masonry work too... Might not light it on fire but it will chip/fragment and generally be a pain.

Rudd · Aug 15, 2016

I have a personal knowledge of exploding concrete. Not something I care to revisit.

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