cutting bladesteel with plasmacutter

[M Wadel]

can you rough cut (cut the shape) blades with a plasmacutter? how much of the blade will be affected by the plasma (how much will be useless, burnt steel) around the cut? anybody know?

 

[deker]

I know a guy who does production work making swords and cuts all his blanks this way. Seems to work fine for him. Not certain how much he oversizes things though.

If you're using an air-hardening steel you will end up with hardened zones at the cut and I'm not certain how deep the hardness will go.

-d

 

[SR_matt]

the amount of things you have to do to clean it up and aneal it so its all even, etc im not sure if its really worth the time and money unless your doing huge knives or swords, there will be a large heat effected ( affected? hmm which ever is the right one) area since your gona be getting it up to 3000*F+. good luck with it, you can try it on a blade or 2 and see hwo it works, worst case your out some cash and time, best case you fine a new quick way to get your blanks.

-matt

 

[M Wadel]

its only for one blade, just wanted to know if i could use it. but i think ill pass, its thick cpm3v steel, i think ill just cut the blade with an anglegrinder instead so it doesnt harden. anyway thanks for your input guys

 

[Phil Wilson]

M Wadel, I use a plasma cutter for my work. I buy sheet steel and cut it into bars or strips with the plasma cutter. I then grind to the scribe marks for the profile. There is some heat affected area, maybe 1/8 inch. I stay a little further away on the curve of the blade and point, but cut much closer in the handle area. You will find that there is more dross on high alloy stainless grades steels like S30V but it cuts much cleaner on the plain carbon and lower alloys like AEB-L. I jsut got tired of buying bi-metal band saw blades. Be carelfull of the smoke and wear a good respirator when doing this work. You do not want to inhale vaporized chrome or Vanadium.. Phil

 

[NDallyn]

You will have some hard spots if you cut it with an angle grinder as well (abrasive cutting discs at high rpm = heat). I originally thought of using a grinder (I'm a welder so I have a couple) but was warned against it. Your best bet is to use a cold cutting method. Before I went out an bought a bandsaw I cut all my patterns out with a hacksaw. It works great but it just takes a while.

 

[NDallyn]

I see on your profile that you're a machinist so I guess you could always try cutting out your pattern with a small end mill if nothing else (probably more time than it's worth though).

 

[M Wadel]

i have access to a waterjet, the only problem is that it costs 200 dollars "just to start it up" and the bars i have will be too small (and the pressure too high) to secure while cutting them. based on phils advise i might try the plasma anyway.

i have carbonfiltermasks from 3m, the are made for protection against paint and thinners and not really for metalvapours, but still carbon filters, will they still work you guys think?? i know vanadium is really nasty stuff (vanandiumpentoxide) that will destroy your whole body, hypersensitivty to chemicals etc. so i really want to stay safe while doing the cutting.

 

[SR_matt]

im not sure if you are able to but cutting out side would provide much better air circulation and less of the bad chemicals around you.

not to hijack but by using an angle gringer will the hard spots end up hurting the over all knife of jsut make it a little harder to shape mayby?

-matt

 

[shaker]

if your water jet "guy" charges you a $200 minimum,,then you need a new waterjet guy. my local water jet guy charged me $13 per blade to do three blades. So he has no minimum charge that I know of .Waterjet is the way to go if you dont want to mill them out. The last 5 blades i have done i milled the profile out for each blade. It only took about 30-40 mins each blade IIRC.
,,,shaker

 

[M Wadel]

if your water jet "guy" charges you a $200 minimum,,then you need a new waterjet guy. my local water jet guy charged me $13 per blade to do three blades. So he has no minimum charge that I know of .Waterjet is the way to go if you dont want to mill them out. The last 5 blades i have done i milled the profile out for each blade. It only took about 30-40 mins each blade IIRC.
,,,shaker

its actually a friend of my father (the shop next door), and i was told that that was about what it costs just to start the damn machine (ok it might have ´been a little too much, but it was "expensive" just to turn it on) its a very very large machine. i would probably get it for free if they did something similar and could throw my stuff in too at the same time, but then i need some jig or something to hold the bar (they usually do very large plates/sheet), it would probably go faster just cutting it with a plasma or anglegrinder i suppose.

 

[M Wadel]

im not sure if you are able to but cutting out side would provide much better air circulation and less of the bad chemicals around you.

not to hijack but by using an angle gringer will the hard spots end up hurting the over all knife of jsut make it a little harder to shape mayby?

-matt

it would probably be as phil said 1/8 or so or less to remove with the beltgrinder, i bet it gets very hard tho (since there is no tempering just hardening)

 

[Deweyknives]

I cut my bars w/ a plasmacutter but don't do blanks. You will end up with about 1/8" of blued steel. Once you grind beyond that, you should be ok.

 

[SR_matt]

that blue part, from what i understand, is actualy weaker so it shouldnt be hard to grind through. if im wrong please correct me but from my experances that part isnt harder and is actualy only heated up to 5-700 *F so if any thing it will soften it.

-matt

 

[M Wadel]

dont know really but i think most steels are delivered in a "spheroidized annealed" condition (it takes several hours at high temperatures to get there then turning the temp down very slow) which is the easiest to work with, all other conditions than that is harder to grind etc iirc (i might be wrong tho)

 

[SR_matt]

the steel i got in (01 carbon) said it was annealed already but when i put it in my charcoal gheto "forge" and anealed it, it seemed to me like the metal got softer... but now i have power tools so its ok
-matt

 

[M Wadel]

ok so here is what i did, i cut the blade with a hacksaw at first, didnt like it (even tho i got bimetal blades, imo hacksaws are only good for Ti and sometimes aluminum) then i found the angle grinder, and let me tell you, just programming a cnc machine takes more time than profiling a blade imo, it took like 5 minutes for this large blade, the rest i do on a beltgrinder, couldnt be more happy anglegrinders are good enough imo if i save a minute or 2 who cares, it went smooth enough.

haha my first real blade, feels so fu--ing good. im gonna try to make it with as little as possible powertools from now on so i know/feel its "handmade", because this one is for me.

 

[Steve Hayden]

I used an offset grinder for years, and still do if I am just going to cut out a blade or two. For more blades, I put a 10" metal cutting disk on my table saw and cut out the rough profiles with it. It works very well.

Use a respirator for tool and stainless steels.

 

[Alan Molstad]

back about a year ago my brother-in-law and I went into town to visit the local welding shop.
While there we got to talking about the fact that I like to make hunting knives in me free time.

The sales man said he cut knives out all the time with his shop plasmacutter.
Now at that time I had never heard of a plasmacutter yet.
I knew that some knife makers had told me that i cant just cut a knife out with a O/A cutting torch right on the lines as the heat of the torch effects the steel and it does not leave a true clean edge.

I told the salesman this and He smiled and took us back to the shop area and showed me how easy and fast he could cut out a knife.

he drew a knife pattern on some steel ,
grabbed the plasmacutter,
and just ran it right around the pattern,

How fast did it cut?
well, as fast as you read this sentence and he was done.

The knife fell to the floor and he picked it up with his fingers...
It was cool ....
I dont understand how the plasmacutter works, But I saw first hand that there was almost ZERO heating of the blade .....

 

[NDallyn]

Yes, a plasmacutter is a lower-heat cutting method than a torch and yes you can just grind away the kerf to get rid of the heat affected metal. On regular carbon steels this will not be a huge problem (you can grind away on your blank and not have any issues 99 times out of 100). Where you will run into trouble is in cutting stainless and high alloy, air-hardening steels, especially steels that contain a borderline amount of chromium for stain resistantance. The area around the heat affected zone (which may not include areas that are visibly blued) of the cut can lose it's stain-resistent properties. I have seen this happen on 300 and 400 series stainless steels on different welding jobs as the result of preheat, welding, and material prep (cutting with a plasma-cutter). I would absolutely hate to spend 20-30 hours on a blade only to have it develop surface rust spots in a month or two. By all means use a water table if you have access to one, but if you don't, save yourself the "what if's" and use a hacksaw or bandsaw.