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Thread: Plasma Cutting Tubing

  1. #1
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    Plasma Cutting Tubing

    Hi All,

    What is the best way to guide a cut on tubing with a plasma? I have a Powermax 30 Deluxe so I have the deflector for the nozzle too.

    Has anyone come up with a good way to guide for various sizes of tubing, both round and square? I was thinking maybe a piece of aircraft cable wrapped around but it might not bend around the corners very good and then how to attach the ends without a twist. I thought of oversized tubing too but then you need a whole series of tubing sizes for each different size.

  2. #2
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    Re: Plasma Cutting Tubing

    Freehand?

    Honestly I don't think there is a magic toy thats going to do what you want. A lot of guys misunderstand plasma. When you boil it down to the basics it's really no different than a OA torch in principal. To cut tube well you will need to cut each side, one at a time on sq tube.

    One difference with plasma on thin metal is you need to move fast to get a clean cut. I had some issues last year cutting SS sheet with my Hypertherm 1000. Hypertherm rep was at the LWS one day a month back when I stopped in to get some wire, doing demos. I mentioned the issue with him and then went back to the shop and grabbed a piece of scrap from that job to try and determine why I was getting such an ugly cut and having warping issues. The reason came down to either low air pressure, which I seriously doubt, or just plain not moving the torch fast enough. Even with his smaller demo machine we could zip thru that scrap SS with a clean cut almost 3 to 4 times faster than I had been doing with a very nice cut. Straight lines were easy to cut with a straight edge. Complicated start stop cuts were harder to keep the torch moving fast enough to get good results unless you free handed the cut and accepted the loss of accuracy. On your tube you are going to have a hard time moving the torch fast enough over the short distance. Small round tube where you have to constantly swing the torch as you rotate around the piece will be an even harder PITA.

    I've used the plasma to cope pipe as well as channel and large tube, just like I can do with the torch. Free hand for the most part. Small square and round tube, I can do a nicer, more accurate cut, with straight cuts on either my chop saw or the band saw. Probably as fast or faster than you can lay out and cut with the plasma.


    Don't get me wrong, plasma has it's place. Flat sheet is where plasma excels. It's darn tough to cut that with the chop saw or most band saws.
    .



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  3. #3
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    Re: Plasma Cutting Tubing

    There's gotta be a good way to do it.

    Same as an O/A in principle that there is a pressurized plasma gas both melting and removing the metal BUT with an O/A torch you don't have a relatively cool edge of the tool very close to or resting on the work that could be used up against a fence, right?

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    Re: Plasma Cutting Tubing

    For tubing I use flexible pipe as my guide as I drag my plasma torch around the tube. It helps keep the cuts straight
    For squares I have been know to use strips of cardboard wrapped around the square as my guide. Yep the cardboard burns away as you cut but if you use speed of solid strips it can be done.
    Co-Own CNC shop:Miller :1251 plasma cutter, MaxStar 700 TIG/Stick, & XMT 456 Multiprocess Welder.& 2 Hypertherm HPR260's Plasma Cutter

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    Re: Plasma Cutting Tubing

    Quote Originally Posted by salem747 View Post
    There's gotta be a good way to do it.

    Same as an O/A in principle that there is a pressurized plasma gas both melting and removing the metal BUT with an O/A torch you don't have a relatively cool edge of the tool very close to or resting on the work that could be used up against a fence, right?
    Well O/A isn't really a plasma but you are heating and blowing away the melted material. As far as O/A not having a cool edge of the tool, it's the back wash of the initial preheat that causes issues. I've used thin plywood and Masonite to do quick dirty templates to cut with O/A and managed to get several items cut from the same template. If the torch is adjusted right there is not all that much preheat wash on the sides. I'm talking about 1/4" and less for the most part. I'll usually dampen the wood to help minimize damage if I want to try and do multiple cuts from the same pattern. I wouldn't want to use say plastic as a guide for either O/A or plasma, but I'd try it with plasma in a tight pinch as the preheat is almost instant.


    I'm not saying it can't be done, just that you won't get as nice a finish as you would get with say a saw, or plasma on sheet where you can get the right speed. I can manage to probably find a way to cut metal with just about any cutting tool. It just won't be as fast or clean as the proper tool.


    Part of this may be my idea of what you want to cut. I'm thinking you are talking about 3/4"-2" sq or 1 1/2"-2" pipe in half (or at least 2' lengths). If you are talking 6" square or 10" pipe I can see plasma working quite nicely.
    .



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    Re: Plasma Cutting Tubing

    You mean like that bendable copper tubing?

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    Re: Plasma Cutting Tubing

    I'll have to invent something and all y'all will make donations to the "My Next Overpriced Tool" fund to have one!

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    Re: Plasma Cutting Tubing

    I had to cut down all the spiral stair case treads for a wooden stair builder that bought a prefab spiral staircase. But the homeowner wanted to match the specs of the original contracted wooden set of stairs. Even though they are two different jobs.

    It was probably going to cause headroom problems, but the business owner finally gave up and said "Well alright". and added in one more step.

    I got the job to cut 3/8" off each ring welded to each tread. I got the next size up pipe, put a set screw into it. And away I went. It aligned itself and made for a great guide. I barely had to sand each ring after I cut them.

    I like the aircraft cable idea. You could make a cute little tool to go from maybe 1.25 to eight inch square or round tube. But you would start to fray the soft thin stranded, usable cable with the hot slag that flies near the cutting zone. The heavy strand cable would be to hard and stiff to get taunt.

    A bicycle chain might do it nicely though. I just bought some nice little chain, much smaller then bicycle chain, from Beardslee Transmission near where I live. I will give it a try and let you know. It would be easy to make something to lock the chain tight. That small chain could go around even small inch tubing.

    Sincerely,


    William McCormick

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    Re: Plasma Cutting Tubing

    If I have multiple pieces to cut I generally fabricate a cutting template that fits over the tube or pipe that I need to cut. I have a job that I do often in my shop that involves a 45 degree cut on some 2 x 3 x 1/4" wall rect tube......I can set my horizontal bandsaw up to do this.....or I can use a 3 sided guide and use the Powermax30...or Powermax1000 hand torch. If I'm doing multiple identical parts I'll spend the time setting up the band saw....if I need just a few...the plasma is much faster, although requires a little grinding to make the 45 degree cut pretty. The guide is just some 1/8" steel plate welded together to fit snugly around the outside of the 2 x 3.....with a 45 degree shape one side and a 90 degree on the other for cutting to length.

    I used to do a lot of roll cages for race cars....and custom fit cages for street/strip cars....the tubing was 1-3/4" .090" wall......I made a template for fishmouthing the tubing out of some 1-3/4" id fiberglass tube....it fit snugly over the steel tube and made a great guide.....and it didn't get hot like a steel template.

    The trick with plasma on thin wall tube? Use the lowest power nozzle and turn the power down...once you match the speed that works for hand cutting and the power level...you can control the dross and heat input pretty well.....it just takes a little practice and the right equipment. I use my Powermax 30 at around 20 Amps for hand cuts that require any finesse on materials thinner than 1/8".....if I am doing straight cuts with a guide....then turn the power knob all the way clockwise.....or go get the Powermax1000 torch!

    Jim Colt
    Last edited by jimcolt; 11-13-2009 at 06:56 AM.

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    Re: Plasma Cutting Tubing

    I thought of that too Jim/William, using the next bigger size material as a guide but I thought it would suck to have to have 20 different templates for the various sizes of tubing I use for different projects. I was wondering when using cable (ATV winch cable 3/16" aircraft cable) what to do with the spot where the ends of the cable come together, since you would have a gap and whatever you are using to cinch it down in the way. But you could just turn clock it to a different spot that you have already cut! Something flexible has to be the way. The chain idea would work but chain is kinda bumpy too, I know the chain you are talking about, like small bike chain right?

  11. #11
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    Re: Plasma Cutting Tubing

    Shold work pretty well....I don't think splatter from the plasma would be an issue if you spray some mig anti spatter spray.

    Jim

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    Re: Plasma Cutting Tubing

    Well Jim has the right idea as that is what I explained I do. I did make some forms/guides using slightly larger tubing and square stock it works great. On those forms/guides I drilled and tapped for the installation of set screws to tigthenn the form/guide to the piece I am cutting. With the thumb set screws they go on fast and hold tight! Plus with the set screws inside the outer edge of the form/guide you do not have to deal with the bumps of chain, cinchs or cable overlap.

    Ps if you think the cost of making to many guides/forms is to high try going to your local scrap yard. You'll be able to find used or n ew pieces to make those forms & guides for pennies on the dollar.
    Last edited by specter; 11-13-2009 at 08:29 AM.
    Co-Own CNC shop:Miller :1251 plasma cutter, MaxStar 700 TIG/Stick, & XMT 456 Multiprocess Welder.& 2 Hypertherm HPR260's Plasma Cutter

    Sorry I had a bad stroke but now I am back.

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    Re: Plasma Cutting Tubing

    That is why I mentioned the bicycle chain, or the smaller chain I have, which I am going to test out. That should be easy to lock tight.
    They used to have a chain oil filter wrench years ago. I bet that would work on larger tubing.

    Sincerely,


    William McCormick

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    Re: Plasma Cutting Tubing

    For round tubing I screwed some fixed casters upside down on a 2x4. Take a few of these, lay the pipe on top. Hold the torch steady (against your leg, floor, table top, blocks, whatever). Start the cut and spin the pipe with your other hand. You'll need 4 of these 2x4 setups for long pieces, two on either side of the cut. With small drop offs you can get away with two setups.

    For square/rectangle tubing I usually scribe a line with a small square and cut each side one at a time. Watch out you don't cut the adjacent wall at an odd angle when starting and finishing the cut. Try to keep the torch perpendicular to the tube.

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    Re: Plasma Cutting Tubing

    Here's a good way to do it . . . but it might be overkill for your situation.
    But find somebody who has one:

    Plasma for Automated Structural Steel Fabrication

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