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I had this piece of 2x4x3/16 tubing that I cut in half to make some cap for 2x10's for some horse stalls. I don't know if this is expected, but it warped really bad .I cut it into 4 and 6 foot pieces. so it's really not noticeable. But if It needed to be straight, I would have been sunk. For the record I used a Thermal Dynamics cutmaster 38. Did I do anything wrong, or is that just a consequence of plasma cutting tube in half? Attached Imagesars sine scientia nihil est
Reply:You're pretty much stuck with that man, at least as far as I know. It's going to happen to a certain extent when you rip a tube length wise like that. You can minimize it by cutting faster. If anyone else has a trick to cure this I'm all ears.
Reply:Cutting by mechanical means (saw, grinder) is the only way to ensure no warping with that type of long cut, all on one side of a thin tube. A table saw that can spin slow enough to run a carbide tip metal cutting blade would be a good choice. A mill would also be a possibility. Or free hand it with an angle grinder with a cut off disc, or use a carbide metal cutting blade in a circular saw with the tube clamped to the table with a fence to guide the saw.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:If you want to understand what happened, the long version is found in the Lincoln Bible; the short version is that, while cutting, you heated to redness/near melting temperature, a small part of the tube along the cut. Because it was still attached to the cold metal, it couldn't expand in all directions but being pliable, it could expand in one or two. When it cooled down, it did what most materials do when they cool; it shrank, but now in all directions. Still being attached to the cold metal which didn't shrink, the resultant stress caused the whole piece to curve a bit.The curvature is fairly small because the plasma only heated a small part of the nearby metal; it would be worse with an OA torch which would have heated more nearby material.
Reply:Originally Posted by DesertRider33Cutting by mechanical means (saw, grinder) is the only way to ensure no warping with that type of long cut, all on one side of a thin tube. A table saw that can spin slow enough to run a carbide tip metal cutting blade would be a good choice. A mill would also be a possibility. Or free hand it with an angle grinder with a cut off disc, or use a carbide metal cutting blade in a circular saw with the tube clamped to the table with a fence to guide the saw.
Reply:Thanks for all your replies. I was pretty shocked when I broke the 2 halves apart and they snapped into a giant 'C'. I wasn't expecting that. You learn something new every day. Now I know.ars sine scientia nihil est
Reply:Are you going to cut any more?My name's not Jim....
Reply:Originally Posted by Oldiron2If I had the option, I'd use a band saw.
Reply:Originally Posted by DesertRider33Cutting by mechanical means (saw, grinder) is the only way to ensure no warping with that type of long cut, all on one side of a thin tube. A table saw that can spin slow enough to run a carbide tip metal cutting blade would be a good choice. A mill would also be a possibility. Or free hand it with an angle grinder with a cut off disc, or use a carbide metal cutting blade in a circular saw with the tube clamped to the table with a fence to guide the saw.
Reply:On machine plasmas often times the part is submerged under water to control warping. Don't know how exactly you could pull that off here though.Vantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.
Reply:Like Dave says, the whole thing is under compression from the process that made it into a tube to start with. Even when ripped in two with mechanical means the uncut material will try to come out of compression towards the new cut. Not as much as it does with heat but still to a degree. If the curved material in this post is a real problem some well placed nickle/dime sized heated spots along the pieces on both corners would bring it back pretty well. Go slow, you can always fill in the gaps if you need more straightening."The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:Originally Posted by DesertRider33I didn't think of a band saw, due to he was only cutting out one wall of the tube. If his finished sizing requirements allow for cutting through both adjacent walls next to the one he wants gone, a band saw would work. If his size requirements dictate cutting out only the one wall without disturbing the 2 adjacent sides, a band saw wouldn't work. I was thinking of the latter rather than the former.
Reply:Originally Posted by BoostinjdmAre you going to cut any more?
Reply:Originally Posted by dave powelson.....ummm....even when.ripping tubing with a vertical bandsaw, which I've done, numerous times,one will see bowing as the stress still remaining in the tube from the tube millis relieved. This occurs in round, rectangular or square tubing--it's the nature of the beast.
Reply:Something that'll help a bit. If you need two pieces the same length tack them together on the ends side by side with something between them to force the middle apart, pre bending them the opposite way. They'll still bend but not near as much as the stress will be working against each other, make sure you cut them evenly, couple feet one one then the other.......Mike
Reply:I used to have to rip lots of tubing back in my race car days. Some of it was welded seam tubing, much DOM and it all would bow some when cut on a band saw. We didn't have plasma cutters back then. (Nobody needs to know how far back then it was...) I talked to the sales guy from the company that brought our steel and he said the same thing as mentioned in an earlier response, internal stresses in the metal from when it was made. In my woodworking side we find the same thing when ripping pieces of even kiln dried wood. some will stay nice and straight, some will curl big time.Usually with the metal we could press it flat enough to use with good c-clamps, or as the original poster did, cut shorter lengths.Tom Hintz, publisherwww.newmetalworker.comLincoln Pro Mig 180Lincoln AC 255Determination
Reply:One way to counter this, never done it with a plasma but with O/A tractor torch. Use a strip cutter, (make sure you're setting down before you open the link) one torch head cutting the other torch head heating the opposite side. If you inject equal amounts heat on both sides of the box tube the warping will be held to a minimum. Otherwise you'll have to post heat both heels on the convex side of the tube. http://weldingsupply.securesites.com...3-0000||1|751|Dont pay any attention to meIm just a hobbyist!CarlDynasty 300V350-Pro w/pulseSG Spool gun1937 IdealArc-300PowerArc 200ST3 SA-200sVantage 400
Reply:If you have one to practice on, you can straighten that out with a oxy/act. torch. Problem is that with too much heat you'll bow it the other way. I've had to straighten a lot of stuff like that over the years. It can be easy to do - with practice.
Reply:Originally Posted by zoraNope, thank god. I cut about 40' of the tubing in half, then had to grind the resulting 80' of channel edges so that the horses wouldn't cut their tongues when they try to eat the wood that the channel protects. All for free I might add The wife of a friend of mine has a non profit that uses horses to help teach deaf kids. Well, a boy scout is redoing her barn as an eagle scout project and somehow I got recruited to help. Anyways I got to do all the cutting and grinding and he got to weld it all together. Anyways, I'm done now. and I've done my good deed for the day. while I'm ranting I might add, that they didn't do the math right, and after we were done building all the stalls, we had that 16' warped pos in the pic above left over. arrrggghhhhh!!!! If anyone wants it, come get it. The edges are all ground smooth. Yeah, I did rip it into 2 pieces. Next time I'm getting a bandsaw though |
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发表于 2021-9-1 00:26:30