Plasma cutting

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Happychicken, Jan 8, 2020.

  1. Happychicken


    Nov 14, 2018
    Hi I am looking for a more efficient way of cutting out blanks for kitchen knives. I have a Milwaukee porta-band but it’s god awful loud and I only can profile blanks a night most of the time. The saw wakes up my kids and I can’t use it when I need to. So I have been looking at a plasma cutter it looks a lot faster then the bandsaw. I have read many threads here that seem mostly negative to using a plasma cutter which is why I ask-

    do knifes profiled with plasma have to be annealed afterward?
    Does plasma cutting ruin the carbides of steel it touches? If so how far back would one need to grind to remove?
    Is there some steal it won’t work with?

    Thanks for any input!! Mike
    Stang Bladeworks likes this.
  2. Stang Bladeworks

    Stang Bladeworks

    Feb 19, 2018
    I would look into waterjet. Its cheaper than you think and much more precise.
    Pinoy Knife likes this.
  3. JTknives

    JTknives Blade Heat Treating Knifemaker / Craftsman / Service Provider

    Jun 11, 2006
    He is looking at buying a plasma cutter I’m guessing so water jet advise does him no good. And you don’t have to clean up that much material from the HAZ.

    No plasma cut blades for not need to be annealed after cutting. I cut tons of blade blanks with a plasma and thy come out perfect. I leave .02-.03 per side for clean up and haz removal by the customer after heat treat. But I run a CNC table so I’m able to adjust cut speed to give me the smallest curf and haz. If cutting by have you would want to leave probably 1/16”-1/8” depending on how steady you hand is and how quickly you cut. The slower you go the more heat with transfer to the steel. But remember just because steel get hot does not mean it has been damaged. The very edge of the cut will be glass hard because that was once liquid but it’s not very deep. If you want to see what plasma cut do you can always order a few blades from me.
  4. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    Plasma cutting has ben used for blades for years. Just leave a bit to grind clean. If cutting high alloy or stainless, it might be a good idea to run an annealing cycle before HT ... or just HT and grind hard.
    Stang Bladeworks likes this.
  5. Stang Bladeworks

    Stang Bladeworks

    Feb 19, 2018
    He is looking for a more efficient way of cutting out blanks. I thought i would suggest it in case he hadnt considered it. I know I always assumed it was more expensive than it really is. I would have appreciated the advice when I was looking into the same type of thing. I hope it helps someone or at least provides another option.
    Jasoncap likes this.
  6. kuraki

    kuraki Fimbulvetr Knifeworks

    Jun 17, 2016
    If you think the portaband is loud just wait until you fire up a plasma.
  7. Sam Dean

    Sam Dean Gold Member Gold Member

    Aug 3, 2012
    Gotta agree with this; a plasma cutter isn't exactly a quiet option. Especially when the air compressor kicks on.

    From the ones I've used, most cut carbon and mild steel the best. Stainless seems to have a little more slag & slightly larger heat affected zone. Regardless, you can blank a blade out in stainless or carbon just fine as long as you leave a little excess material to grind off. You could even use an oxy-acetylene torch with a little practice...

    Would it be possible to spend the plasma cutter funds on some sound deadening insulation instead? My "workshop" is currently a room in my basement (living room right above me), but is well insulated. The noise transmitted above is minimal.
  8. Happychicken


    Nov 14, 2018
    Let me start by saying thanks to everyone for their input!
    If the plasma is way faster than the port-a-band maybe it’s still worth it. However I am using stainless almost exclusively as I am a wanna be kitchen cutlery maker. However I am an excellent knife steel ruiner!! I am mostly using nitro v and aeb-l as they seem more affordable and one out of five knives I try to grind make it to the kitchen.
    I also wonder if I am not giving enough pressure when cutting the blanks with bandsaw. Maybe this is why it takes so long. But I did ruin a few bandsaw blades quickly when I “pushed” the steel to hard when cutting.
    Has anyone noticed AEB-l jacks up their saw blades? Maybe just me
    Anyway the best I can afford in a plasma right now is a Chinese made model around 500 bucks. I don’t want to do what I did with the grinder and buy two before I ultimately realize that I should have gotten the “expensive” one in the first place. I gave my 1x30 rykon to a kid at church to try to make knives with and I would feel directly responsible if he tried to jump out a window because it’s so frustrating to try to make a knife with.
  9. Happychicken


    Nov 14, 2018
    Sorry what I mean is would I get enough plasma cutter for 500 bucks to cut through 1/4 and less stock? Cleanly with little slag
    DustinY likes this.
  10. scott kozub

    scott kozub Basic Member Basic Member

    Jan 1, 2018
    I make my knives from AEBL and use a plasma and a hf horizontal vertical bandsaw. I have zero issues with plasma except that when using steel plates the blanks can come out warped but they're easily straightened before cleaning and hardening.

    My last batch of knives I used my bandsaw and like it better. I could lay out the knives much closer to each other without the risk of slipping free hand with the plasma. As long as you have a good blade it's pretty fast. I usually cut .118 AEBL
  11. JTknives

    JTknives Blade Heat Treating Knifemaker / Craftsman / Service Provider

    Jun 11, 2006

    I spent $1400 on my hand plasma cutter and I have never regretted it. You get what you pay for. It is difficult to get a good clean slag free cut with a good plasma cutter and even harder with a cheep cutter. But I would look into what it would cost to have someone like my self cut tour blanks compared to the number of blanks you process in a year. a plasma has other expenses that add up as well. Need a decent air compressor and some way to dry the air. This is not one of those little dryers that look like a filter. A refrigerated dryer or a regenerating desiccant air dryer. Wet air in any amount will quickly burn up consumables which are pricy.

    it is probably the cheapest way to cut steel in the long run but if you making 10-20 knives a year it’s not worth it really.
    Ken H> likes this.
  12. Storm W

    Storm W KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Feb 19, 2019
    JT is pretty affordable and can heat treat the blanks as well for a good price. If you are going to do a few pieces of the same pattern its definitely worth it. Having him cut is by far the quietest option.

    If you do get a plaz unless you have very steady hands you will have a fair bit of trim to grind off anyway so I wouldn't worry to much about the cut edge making it into your final blade.
  13. Sam Dean

    Sam Dean Gold Member Gold Member

    Aug 3, 2012
    @Happychicken Do you heat treat yourself, or do you have some other company do it?
    This is very good info. That $500 plasma cutter is going to cost a LOT more in consumables and other accessories just to run it, unless you already have a good compressor and dryer.

    I had JT cut me some blanks. At first, I was a little put-off on the price. Then I started adding all these things together:
    • My time - cutting, profiling, drilling, straightening.
    • Cost of material
    • Shipping costs - for initial material, shipping costs both ways to have it heat treated, shipping costs of belts & blades
    • Consumables - belts, blades, drill bits, etc..
    • Heat treating cost
    I send him a drawing, he sends me back a hard, straight, surface ground blank ready to go. Turns out, it's actually a bargain, supports another small business and lets me focus on doing what I really want, which is making knives. I'm just a hobbyist with limited play time and a full time "job". I'm now convinced using a service like this actually costs me less than doing it all myself.
  14. Happychicken


    Nov 14, 2018
    Thanks JT and Sam. I get that making a knife is expensive anyway you look at it.
    I have someone local selling a miller plasma fairly cheap so I’ll see if that goes through. I have taken enough tools back to harbor freight to not count on stuff made in China. Although I keep hearing good things about their bandsaw... go figure.
  15. Stromberg Knives

    Stromberg Knives Knifemaker / Craftsman / Service Provider

    Jan 3, 2015
    Regarding the bandsaw blades. Choose good quality blades (I use Lenox) with the correct blade construction (probably bi-metal) and the correct TPI in accordance with the material you're cutting.

    In my experience a lot of users forget to break-in the blade before going full speed ahead. Here's Lenox's take on blade break-in:


    And you'll find more useful information here:
  16. JTknives

    JTknives Blade Heat Treating Knifemaker / Craftsman / Service Provider

    Jun 11, 2006
    I would do some research before jumping on a used plasma. We have a oldish Hobart plasma at work that you could not pay me to take. Sure it works but it does not have shielded consumables so you have you use a funky attachment to keep the shield from touching the surface. Once you find out the model post it here and I will look it up and see if anything stands out. Plasma cutting technology has come leaps and bounds in the last 10 years or so. What the new machines can do is impressive to say the least. Hypertherm is what I use and is considered the best brand out there. Thy are on the leading edge of the industry. My hypertherm can run off 120v wall outlet and I have cut up to 1/2”. When plugged into 240v I have cut 3/4”+ and the unit is the size of a small mail box.

    so get the model number and post it.
    Storm W likes this.
  17. Happychicken


    Nov 14, 2018
    I read that bandsaw break in article when you posted it to another thread it came up in the search!! Thank you very helpful

    Plasma is a miller 375 extreme it looks like it gets very good reviews

    I am currently using the Milwaukee extreme (a lot of tools are extreme these days) bandsaw blades
  18. Happychicken


    Nov 14, 2018
    Plasma was a total scam gotta love craigslist “send me money and I am to overnight item of free shipping”.
  19. ten-six


    Mar 11, 2017
    Don't take this the wrong way....

    It sounds to me like you're trying to get ahead of yourself. Learn to use the tools you've got to their potential. To me there's no reason, from your own admission, for you to even consider a plasma cutter right now.
  20. Happychicken


    Nov 14, 2018
    Good point for sure! My argument would be the more time I spend grinding blades the better I will get. So if I can use the time of profiling blades to grinding blades I will hopefully get better faster.
    But your other Point is a great one! I watched several videos of people cutting with portaband and I have to admit I was not using that tool to its full potential!! I am cutting about 2x as fast now

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