Profiling 1084 w plasma cutter

schmittie

schmittie

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Nov 28, 2009
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I used the search and tried to find some information on profiling with a plasma cutter. (some of those thread really got off on a rant) I couldn't exactly find what I was looking for. Much of what I found centered around cutting hardened steel. I have 1084 1/8" on its way over from Aldo and some of my welder friends are trying to talk me in to using their plasma cutter to save some time. Is there any danger with this idea? I realize I should cut the shape out a little big then grind down. What do you think?
 
Plasma would blow through 1/8 stock pretty fast. I dont think you would have too much of an issue, aside from excess waste.you will want to rough profile about 1/4" bigger due to the rough edge produced by the plasma cutter. I am sure it can and has been done.

Actually upon further thought, 1/8" stock should cut pretty decent with a plasma. Maybe shoot for 1/8 oversize. should get hot enough to burn out carbon in the blade if you cut oversize.
 
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I profile all my blanks with a plasma. One thing I do is drill the tang holes before cutting in case of hardening. Otherwise just a steady hand is needed. Make a pattern to follow when you find a knife you wish to repeat. My plasma cuts about 3/16" from the outside edge of the tip. Jess
 
Are your welder friends any good with a torch? I can cut a lot faster and cleaner with a torch than I can with a plasma cutter. But that's just me. With 1/8" stock you'll have to move pretty quick. I think a template is probably a good idea.
 
Yup, make a template and cut big. The HAZ (Heat affected Zone) will be somewhat hard after cutting, I'd recommend removing it all.
 
I have never used or have seen a plasma cutter in use. My friend who uses it claims it cuts metal so fast that the metal does not get hot. Is he just pullin my leg? I was hoping there was some truth there because then there would be less of an issue of altering the hardness. The way I see it the metal is going to get hot no matter what you cut with, bandsaw, grinder, plasma cutter.
 
Your friend is wrong, I cut with a plasma cutter and the scar on the underside of my forearm, and the bolt I once cut and ended up melting into my shoe both says it gets real hot. Nice thing is you can move fast and get a fairly clean cut, I think it's a cleaner cut than the torch, when they're both done right, but I can't remember the last time I used the torch for something real thing so maybe my memory is fuzzy. plasma cutters are just super easy to use. (I still love a cutting torch, and prefer it for the pure fun, but for many things, especially small or more freehand the plasma cutter rocks).

Red
 
Compared to an O/A torch, it doesn't get very hot. That is, the ionized stream of gas and metal being blown out of the kerf is in excess I believe of 10,000 deg. F, but there is very minimal heating of the surrounding metal. (Cut a circle of sheet metal 2" dia., it's then possible to immediately pick the piece up with bare hands by grasping the center.) It does cut very quick and clean, on clean metal with a steady hand. The heat affected zone will be small, about 1/16" oversize on all sides. Not too much more than a blank chunked out on a bandsaw.

I say go for it. But practice on some mild 1/8" sheet for a bit, first.

Edited to add: not trying to contradict the above commenter, the edges of the cut will be hot after cutting, and the thicker the stock the more heat tends to build up.
 
You are melting/vaporizing the edge even if a thin layer .Happens with EDM also .I'd temper it afterward or at least grind off some material.
 
schmittie said:
I have never used or have seen a plasma cutter in use. My friend who uses it claims it cuts metal so fast that the metal does not get hot. Is he just pullin my leg?
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He's pulling your leg. The plasma arc is around 45,000 °F -- it leaves a very hard kerf from the vaporized metal. You can just grind it away, but I find it's easier to just rough out with a vertical bandsaw.
 
schmittie said:
I have never used or have seen a plasma cutter in use. My friend who uses it claims it cuts metal so fast that the metal does not get hot. Is he just pullin my leg? I was hoping there was some truth there because then there would be less of an issue of altering the hardness. The way I see it the metal is going to get hot no matter what you cut with, bandsaw, grinder, plasma cutter.
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It gets hot, but because you can cut so quickly you will have less of a heat affected zone.
 
Carl_First_Timer said:
You are correct, but comparing Plasma to edm is a bit of a stretch. :rolleyes:
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I don't know, I think they're fundamentally similar in some ways. The arc and spark temperature and resulting plasma and hard residual scale have a lot of similarities.

I wouldn't recommend plasma for air or oil hardening steel, but (assuming you grind away the burnt steel) I think it would work okay for 1084.
 
Nathan the Machinist said:
I don't know, I think they're fundamentally similar in some ways. The arc and spark temperature and resulting plasma and hard residual scale have a lot of similarities.
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He is correct and I stated that, liquefying and solidifying are involved in both processes.

I have, and use both technologies. The reason I was saying comparing the two was a "stretch" is that I can get to pure, unaffected metal, on a hardened piece of steel that was EDMed (with finishing passes) to +/-.0001 using a Scotch-Brite pad.;)
 
Nathan the Machinist said:
I wouldn't recommend plasma for air or oil hardening steel, but (assuming you grind away the burnt steel) I think it would work okay for 1084.
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Thanks Nater. I just got the steel today so I hope to start soon. I promise i will grind away the burnt steel. I'll keep everyone posted of how things go this time. Seems like the guys appreciate WIP pics more than just the finished product.....at least when it comes to us newbies.
 
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