Cutting with torch, need advice,1st time.

[pa.rich]

Alright you great metal workers, I really need help. I am working on an old dump body. It has lots of rust. I cut most of it out with a saws all and grinder. Then comes the part I need advice on. The body is off the truck, lying bottom up in my garage, and it has 2" corrugated metal under the flat bed plating and the corrugated is sandwiched inbetween the frame members and the plate steel They are not thick, but about 1/8" thick each. I want to save the frame but cut across the corrugatedand the floor plate and dispose of them I want to replace the corrugation with something else. Here is my question. I never used torches before today. I was able to cut the plate where the corrugation was gone, but I couldnt cut both. Through the valleys of the corrugated, it would cut, but the humps I could only get through the tops. Is this something impossible because of the 2" air space? Do I have to go back to reciprocating saws all again? I already went through many blades.Please help, cant afford to buy a body ,so I would spend some sweat instead.Spent alot of bucks on this torch set only to be disappointed.Can someone advise?BTW, using a #1 tip and followed directions in the manual for the pressures at the regulators.

 

[rdixiemiller]

It can be done, but the torch has to maintain a constant distance from the steel. If you are cutting corrugated, you will have to move the torch up and down with the corrugation pattern. If there is flat sheet over the corrugations, it will have to be cut loose first. You will not be able to cut through the flat and the corrugated at the same time unless you have a really big torch tip. You might try a demolition saw with a 10 or 12" abrasive blade. They are pretty good for this kind of work.

 

[pa.rich]

I was afraid of that. Thaks RDM, guess I will go back to sawing.I may just cut out the hoist area and scrap the rest of the bed floor. Looking at the bright side, at least I made some progress.

 

[Blythewoodjoe]

You can cut with a torch an inch or so from the surface, if you start cutting near the surface. In other words if you start to cut the corrugated metal where you can reach it with the tip, you might be able to cut the lower parts if you don't loose your cut. You will never be able to start a cut with the torch an inch aways.

One other thing you might consider is taking a welding machine, turn it up all the way and us it to cut the steel out of the way. You will use a lot of rods and you must pay close attention to the metal that will be produced but you can cut anything 1/4" or less in thickness this way. You have to make sure the metal is falling away from where you want to separate the metal. If you are not careful you will build up a bunch of steel and make a bigger mess.

I have demo'ed a lot of junk like this over the years, but I have almost 20 years experience with the torch and welder. This will be a challenge for the beginner.

Good luck,
Joe Trapp

 

[Jones]

Here's something else to consider. If the corregated material is ex-roofing or siding; watch out for galvanizing. The zinc released by cutting is very bad for you if inhaled. Stay safe.

 

[derby]

Good point on the galvanized metal.What if you were to cut the corregated material,and then go back and make a parallel cut an inch away,pull out the corregated and then you would have a clear shot at the steel deck? you will use more gas/oxy but sawzall blades aint cheap either!

 

[acetomatoco]

I would suggest a good course in metalworking and cutting etc from your local community college.. Maybe you could bring your own work there and have expert help and get credit for it... been done many times before.. Some High Schools even have their students in Shop Class work on outside projects just for cost of materials.. ACE

 

[pa.rich]

The corrugate isnt galvanized, but thanks everyone for the cutting advice. That was 1st time cutting and had no idea how. Yes, I could use a class or series of classes. Each trade deserves respect for the skill and knowledge it takes to do it. I build buildings and knowledge is one thing, but the associated skill is something that can take years to develop to become good at the trade. I didnt mean to insult any welders here , by saying one class would make me able to do it. Thanks for the help, though, and I appreciate all the help from everyone. This is really a great site. I am going to send some pictures when I get time, maybe Sunday.

 

[jimk]

More stuff,
Cadmium, as in plated fasteners and parts, is -very- toxic too(death). Manganese, used in many steels, can cause permanent nervous system damage(arc welding rod have it too). Cutting tips need to be cleaned often (with small reamers) to get the best, and cleanest cut. The preheat holes tend to get smaller while the O2 hole cuts best when perfectly cylindrical(thicker stuff). The pre heat (outer) flame's blue tips should just touch the work. That is the hottest part of the flame. Too much preheat can weld thin sheetmetal back together, behind the cut. A neutral flame is preferred,especially for fab work, as other flames contaminate the cut surface with oxygen or carbon. The metal needs to be hot enough for the O2 blast to work.Bright red.A cut cannot be initiated without this. When [after]O2 burns the steel it generates enough heat to cut with out any preheat though this best done only as a demonstration.It can be employed to burn out a broken ex. manifold stud.That dirty thread interface can be used,with a gentle hand [and only O2], to get just the stud.Stainless cannot be flame cut. O2 pressure is usually 2-4X the acetylene. Keep a fire extinguisher(s) nearby. Be aware that spatter balls can roll quite some distance and ignite combustible materials including lint and sawdust under the sheet rock of a stud wall and poly fuel cans. Never use a butane lighter. Horror 'stories' exist of the guy who had a red hot balls of spatter cut a hole in lighter inside the pocket. Turn tanks off when done.Chain bottles so they can't fall over.If they do fall the valve may break creating a unguided missile. Grass fires a concern outside in dry weather.Some fires(inside or out)can smolder for hours, so try and monitor work areas a bit before going away. A fat straight edge can help make real neat cuts.The cut can be increadable thick, with the correct tip and enough O2- Pictured over 5 feet thick in one book I have.JimK

 

[Jones]

All excellent points jimk. Another quirk is that cast-iron can't be cut either.
Avoid synthetic materials for clothing as it'll melt and fuse to skin. Wear leathers or other heavy protection 'cause a red hot drop of metal down the glove, waist-band or boot-top can sure take your mind off keeping the torch pointed in a safe direction. Mind your hoses as the red hot slag can burn through them too. I've personally seen a set of hoses turned into a writhing snake with fiery head. Very impressive and can clear a shop in milliseconds. Some brave soul had the nerve/presence of mind to shut off the gas and oxygen on the way out or the entire shop would have gone up.

 

[devilman96]

Also slam down a glass of milk after welding or cutting on anything you think is galv... This will keep ya from getting sick which often times starts with a head ache, skip the Advil and get some milk in your system...

 

[ARMYMAN30YearsPlus]

This sounds like great time to use a metal cutting circular saw blade and set it to the depth of the lower corregation. I have torch plasma cutter and often forego them to use the saw for difficult cuts like this.

Oh and to add this if you are working near anything galvanized drink lots of milk before and after you weld or cut it.

 

[pa.rich]

Thanks again, it all helps. Another question, how should the flame lookon the torch for cutting?Blue but how long? And does the flame get angled towards the direction of cut or 90 degrees to cut?

 

[Jones]

For preheat: a ring of short 3/8" to 7/16" bright blue points inside the cone of flame. Tips of this ring of flame should just touch the work-- the tip of the cutting torch will be about the same distance off of the metal's surface. Allow the metal to become bright red to orange before pressing the oxy lever; otherwise, the oxy jet will actually cool the metal to below cutting temp.
Everybody's got a different technique that seems to work best for them. I tend to hold the torch tip at a little rake back away from the direction I cut. Seems to blow the slag and molten metal away from the cut so it doesn't flow back in behind me and reweld itself. Mechanical flame-cutting set-ups hold the tip(s) at 90 degrees to the surface because they're cutting clean, flat plate and don't have to worry about the operator's variations in tip speed and distance over the surface. Guys who run a torch on a regular basis can do nice work be it thick or thin but for anything thinner than 1/4" I swear by a plasma torch. Just my two cents.

 

[jimk]

Yea, plasma the best way. Torches, like stick and MIG, the operator needs to study the behavior and make adjustments as needed. Just looking at the work[done] tells a lot. I find thin stuff a pain and for demolition just butcher away.I find anything over 1/8 can be done very neatly(fab). I use a solid 1"x 3" bar(5' long) as a straight edge.Heavy enough so usually don't bother to clamp it.Heavy so does not melt. I drag side of tip on side of bar. It'sfairly easy to keep blue tip on work. I might even grind the surface quickly before hand so pre heat hits a clean,flat and uniform surface. Roughness,paint rust can cause cut to waver. Rate is important. Too fast and cut drops.Too slow and preheat melts surface.I try to think of myself as a machine. Resulting cuts can almost look sheared .This saves time grinding/fitting. I always use 90 unless I want a bevel edge(like for butt joints). Angle can be used to punch holes as keeps stuff from blowing back in your face. Chisel up a burr if stuff real thick. Saves some preheat time. For nice work I usually try and hold torch in one hand and stabilize forearm(or torch) with the other hand [arm]coming in 90 degrees from the side . This seems to give better lateral control.JimK

 

[pa.rich]

Thanks for the tips, I didnt realize that the rust was a problem. And I will try thr heavy bar for a straight edge when I cut something important. Now I see why I was having so much trouble. Back to the job with some encouraging words.My flame was all wrong too, and my distance away from the steel, I wass doing it all wrong.Thanks for the help everyone.

 

[Jones]

Yeah, cutting through heavy rust is like cutting a box of 4th of July sparklers. All that oxygen in the iron oxide gets liberated at once as the torch tip goes by and it can be spectacular. Like JimK sez, a heavy straight edge (1"X3") is a must. I watched a guy waste a sheet of plate because, as he cut, his 1/4"X1" straight edge warped with the torch heat. Long, pretty, sweeping curves though.