Metal workers--Plasma cutting

[DouginUtah]

Please describe the smoothness of a cut done with a plasma cutter. Is it like a cutting torch or more like a cut made with a band saw or ??

[motohed]

Plasma cutters will cut a fine edge as long as you are consistent with the speed and distance from the piece of steel you are cutting. the edge is generally better than a torch . I made a little wheel  mine as I'm not as steady as I once was , you can also set them up on a machine head as well but they are expensive . you will also need a clean air  supply with a good regulator ,  and a good water , oil  separator is a must . I use several with mine . Make sure you have one thats big enough for our job , or all cuts will be ragged , mine will cut 1.25 inches and sever 1.75 inches . I have also used it to gouge out a crack for welding . Good luck  !

[zopi]

Torch or plasma will give pretty much the same results...just depends on the operator...I have a set of pinch dogs a friend made for me..came off an oxy acetylene plotter table...as clean a cut as with a bandsaw...did not even clean em up with a grinder...went right to the case hardening...

[scsmith42]

Doug, it depends upon the operator.  My experience has been that plasma is a bit smoother than oxy-acytelene, but not quite as smooth as a saw.

I sure do like using the plasma cutter though, and not spending $ on acytelene.

[Al_Smith]

Plasma or a torch depends on the operator .FWIW I've cut 1" thick cast iron with plasma which is one thing you can't do with a torch and it was pretty smooth.I've also seen some pipefitters that can cut pipe with a torch nearly as smooth as if it were saw cut .I can on occasion but not as the norm .

[motohed]

We also need to say that what ever you use , plasma cutter or torch the metal must be clean if you want a good cut . No rust ,paint , oil etc .

[Al_Smith]

Well I'll certainly have to say the price of acetylene has gotten outragious .Then I find out only about two companies in the entire world have the rest of the world held hostage .

Some use propane or MAPP but I personally think they both suck .Somehow in my life time I managed to acquire 4 complete sets of torchs .Three from holding my hand up too long at an auction and one I kind of inherited from my deceased father .I use so little of the stuff as a norm any more I only have two sets filled .One at the house and one at my shop .Lawdy if I got all 4 filled at the same time I'd have to mortgage the house .

[DouginUtah]

Let me ask another question here...

What do you guys use to mark on mild steel? (Cross-hairs) I used old, fine Sharpies but after a few marks, they didn't show anymore. Pencil doesn't show up very good.

I bought a white pencil at the fabric store but that didn't work either. What do you suggest I use?


(In case anyone is wondering, I am building a trailer. It was supposed to be just a light utility trailer but I have ended up over-building it.) 

[scsmith42]

Let me ask another question here...

What do you guys use to mark on mild steel? (Cross-hairs) I used old, fine Sharpies but after a few marks, they didn't show anymore. Pencil doesn't show up very good.

I bought a white pencil at the fabric store but that didn't work either. What do you suggest I use?


(In case anyone is wondering, I am building a trailer. It was supposed to be just a light utility trailer but I have ended up over-building it.) 

Doug, the best thing that I have found is soapstone.  Welding supply houses carry it, and I think that even the BORG's carry it in their welding section.

[DouginUtah]

Aw yes, now I remember. Thanks, Scott. Little rectangular sticks about 1/2"x1/8".

[caveman]

I use soap stone, chalk (in a pinch), silver streak pencils (they can be bought at welding supply stores), and silver sharpe markers.  The plasma cutter will usually leave a little slag or dross on the back side of a cut that can be chipped off relatively easily.  When making straight cuts, a piece of angle iron can be used as a fence to keep the cuts straight.  The biggest two benefits of the plasma cutter over a oxy/acetylene rig is 1.  The ability to cut all metals   2.  Speed, Plasma cutter cuts faster with less distortion to thin materials.  The torch is useful when needing to bend or anneal metal as well as cutting.  Caveman 

[Larry]

I don’t have a plasma just because they are so Dang expensive.  I do have O/A torches but don’t use them much for cutting.  I’m always brazing cast so can’t do without them.  A few saws help with the cutting.  Chopsaw, vertical band, and PortaBand.  Even a power hacksaw...I get a kick out of just watching it work.

In the last few years I’ve really started using a right angle grinder equipped with Metabo Slicer for cutting.  I could cut the parts for a trailer just with that one tool.

[Al_Smith]

FWIW in case anyone didn't know they also make soap stone in a round stick form plus a little device with a pocket clip  to hold it .Many including myself prefer this  type .If you so desire you can file,sand of in some way taper the soapstone down to a fine point like a pencil .

For that matter they also make a holder for bar type soapstone .Soapstone has been the time honored method of marking metal for torch layout and works as well today as it did 100 years ago .

[Coon]

Another thing I use sometimes for marking steel is a paint pen.  I try to find the fine tip ones when I can.  The paint inside the pen dries fast.  I get them at acklands grainger or some of the other stores that carry welding supplies.  Oh and don't let those paint pens freeze otherwise when they thaw and you tip them over to use them they will leak all over and make a heck of a mess....  Don't ask how I know.   

[Stump Jumper]

Doug get yourself a scribe to mark the line. The finer the line the more accurate you will be just be sure to wear those glasses.

[Bill Gaiche]

Its really all about the operator and quality of equipment in making great cuts. O/E is more versatile, cutting, brazing and to heat and bend metal. I bought a chop saw when I built my band mill and they make some good quality cuts. bg

[SPIKER]

Plasmas also require consumable parts, the tips and electrodes do get ate up when cutting the higher the amperage the more the tip wears.   so when cutting use the lowest amp setting for the material.   like noted plasma cuts all metals equally well.   mostly good for flat work not quite as well on say I beams or Channel Iron ect...

mark

[DouginUtah]

Yet another question...

What do you guys use to prep metal for painting? To get rid of the dirty, oily film.

I guess I could find someone with a pressure washer but water = rust, so I'm asking if there is a better process.

[shelbycharger400]

doug... 

marking metal.. i use paint pens on dirty or oily, or scaly metal
soap stone is nice, dosnt work on dirty , or wet
the kids side walk chalk works good, in many colors too

metal prep...
light oil, dish soap
heavier oils, i use grease lightning or simple green, i have used an acid wash for light rust too,  anything from a floor broom to a hand held scrub brush and gloves.

cutting ...   
 i love plotter table..  out of my price range
shear...  works awsome...dont have one...
plasma cutter...  its all down to operator AND the machine.  a $1500 chinese plasma cutter... will give you a bad cut!
grinders work as do saws.

[Randy88]

plasma cutters are generally used in thinner metals where a torch will warp the metal, sheet steel is an excellent place to use a plasma cutter, as for the cut, it depends on the thickness of the metal if your comparing it to a torch as to how it cuts, torches don't tend to cut thinner material very well with a smooth edge whereas a plasma will do an excellent job at that, in thicker metal they are about the same, depends on the tip condition and the operator.    As a general rule of thumb around here we use a plasma on thin stuff and a torch on thicker material, say over a 1/4 inch thick and above is torch below is plasma.   Plasma also cuts cooler thus lower warpage on thin metals.

 As for metal cleaning, the best all around way I've ever found to do it to take the finished product to a galvanizing plant and have them hot dip it for me, they acid treat and wash it then dip in in galvanizing and its done, for a fraction of the cost of painting and all that, but that's mostly for projects I make for outdoor use, signs, an atv trailer, strobe brackets on trucks, toolboxes, those types of projects, anything else its back to using mineral spirits or some form of wash type product and painting it.

[Al_Smith]

When you talk metal prep it can get rather involved .First you have to have it clean,all the mill slag off etc .Slag would require sand blasting .Then acid prep it with "triple etch " or some other product .Give it a good shot of red oxide primer then shoot it with paint .On galvanized  acid prep it then a coat of zink oxide followed by red oxide then paint .

I personally use Rustolium brand myself ,it's never failed me yet but that's just a personal preference .

[mometal77]

Plasma cutters are a great way to cut steel when you do not know if it is Ar400 or T1 steel.  And comes out of a scrap yard.  And you could mess up you ironworker shear not knowing what it is.  The history of plasma cutters are just like the invention of leaf blowers.  Invented by 2 guys in a shop and they went wrong by trying to get their invention out there as the story goes.  There are stories and ideas online where you can build your own online machine.  Thermal Dynamics i think makes the best machine out there.

http://www.plasma-cutter.com/  Just an idea for information.

Plasma cutters have come a long way from just having a transformer and weight in at a few hundred ibs of copper and not being able to cut more than a few gauges of metal.  I have heard of plasma cutting machines that could cut 6 ft thick and rubber walls/thicknesses of nuclear subs.  I cannot wait for the technology to come out we're all you need is a ''small'' box and consumables that never need changing and are reliable.  But then again companies would go bankrupt if not selling merchandise that lasts.  Kinda like that pizza in back to the future 3 or chicken in the fifth element.

Safety:
If you ever cut stainless steel use a respirator and cover yourself from Uv hazards.  When I worked for Haskell Corp. 3 journeymen sheetmetalworkers went to the ER over no masks were used. And never work in a confined space when using them.

http://www.metalwebnews.org is a great site if you have ideas or projects.

[Al_Smith]

Well yeah T1 is some tough stuff .I haven't seen any in years myself .That which was was cut on a flame cutter .Big buckets for Michigan front end loaders and Madsen asphault plant dust collecters back in the day .Lawdy though that day was 40 some years ago when my hair was all one color which it's soon to be again although somewhat lighter than the coal black in the days of my youth .

[mometal77]

T1 is some tough stuff.  Repairing buckets at the quarry. I would use old broken drilling rod. Or it makes good stuff when material goes from a conveyor into a shaker. We're I am you never know what you will find at the recyclers.  A friend of mine ran into a nice sheet of Titanium and they thought it was stainless.  If you have ever welded titanium with a tig welder it omits a white light.  Kinda neat stuff I just cannot believe with the way the economy is going locally here i have got some great findings on tig rod 3/16 to stainless steel rod and i was just in the other day and it looked like someone recycled their whole shop.  I scored on some brand new welding lead at 2.50 ib

[DouginUtah]

Yet another question.

I have spindles with a 6" long 1.25" shaft. I bought 1 1/4" Schedule 80 pipe for the axle. It is 1.278" ID, but it has a ridge (seam) from the manufacturing process which prevents the shaft from going into the pipe. I can't think of a way to get rid of the ridge.

Also, when the ridge is removed, the fit will be sloppy (0.03"). How would you recommend overcoming that and how would you weld the two together--pipe to the inserted shaft. I'm thinking of drilling some holes in the pipe and filling the holes with the weld. Any better ideas?

[isawlogs]

Doug , use an axe file , it comes with a nice handle to remove the ridge,  I really don't think that .03 " is that big of a deal , file till its a tight fit , both spindles will have the same offset that is neglectable. ( Unless you are a purest then .. shime to your hearts content  Or ... Give the pipe a whack with a hammer a quarter turn from the ridge .. that would be my shimming  )
  Once fitted tight , tack weld the end of the spindle to the end of the pipe. Now put the wheels on and check the distance between the rims, if it is same, put a full weld on the spindle & pipe.

 To prep , I only ever use a hand held grinder with a sanding disc the type that has many over lapping leaves of sandpaper attached to a plastic disc. For preping the spindle I would use a grinding disc to remove any oils/rust or paint but only where I would be welding.

[scsmith42]

Doug, Marcel is providing some great advice.

When I have built trailer axles in the past, I would use either a round file to remove the burr inside the axle tube, or more commonly a die grinder with a carbide bit in the end.

To weld the stub axle to the tube, I would do a combination of drilling a few 3/4" holes through the tube and then filling them with weld after the stub was inserted, and then full weld the end of the tube to the stub axle. 

Personally, I prefer that my axle's be as precise as possible, and in order to make sure that the centerline of the tube and the stub axles were true I would use one of two techniques.  If the fit between the two is relatively close, let's say within .050, then I will take a center punch and make a series of deep punch marks on each end of the stub axle, making 3 - 4 rows all of the way around the axle.  When you  make a punch mark a rim of displaced metal is raised up from the punch, and this serves to take up the clearance between the axle and the tube.

If the clearance is too great to be taken up with the punch method, then I will tape a piece of shim metal around the stub axle at each end, close enought to the ends so that the stub is centered but far enough so that the melting tape does not contaminate my weld.

[DouginUtah]

It's been a couple of months since I started this and I have now built two trailers.

One is a 5x10 (somewhat unconventional--actually 5'-4") and the last one is a 4x8 with a 3/4" birch plywood deck--which I bought at Home Depot for half price ($13) with an Ace 50% off coupon.

So, I learned a few things:
I said a Sharpie doesn't work. I was wrong. If the metal is clean and you use a fresh Sharpie it works fine. My first Sharpie was old and partially dried out.

I plasma cutter is really good at cutting a bead when you make a mistake. I put the tongue on with the frame upside down and then put the shackles pointing down. Had to remove the tongue and put it on the other side. Of course that meant that the turn signal wires (running in the tubes) were switched so I had to switch the brown and yellow wires in the tongue.

I used Purple Power to clean the metal. (Intended to buy Simple Green but PP claimed to be a degreaser on the label.)

Utah has a requirement that any trailer over 750 lbs. has to be registered. I made sure these trailers were under that, and will never again build a trailer that has to be licensed which precludes building a dual-axle trailer.


 
 

  

 
 

 
 

 
 

  

 
 

 

P.S. Fenders are not a legal requirement for trailers in Utah.