hot or cold pipe bending

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What say you, on bending 1" DOM tube/pipe with heat.I want to build a bike frame.The sharpest bend would be 40* which there are two of and two 15* bends in two lengths of pipe.There are multiple cross members for strength.Does heating have an effect that would effect safety? Thanks ,Ron
Reply:It will kink.  Unless you want to go through the trouble of packing it with sand, welding caps on the end, heating, bending, then cutting caps off and emptying sand, I would just go get the bends made at a shop.
Reply:Bend radius will play the biggest factor in determining how to do it. Hossfeld and a die would bend it just fine cold. You can heat it with a torch and bend hot fairly easily with no sand and no kinking as well. More info needed. Also, DOM and pipe are two different animals. I would hazard a guess that your inexperience with the right terms, and HAZ from heating, is going to put you into the category of 'probably shouldn't be building a motorcycle frame'.Last edited by walker; 01-28-2013 at 08:46 PM.
Reply:Walker, why don't you enlighten me with some of your wisdom so that I may be educated on this matter.I am very aware of what Drawn over Mandrel tubing is,I have already purchased it,some people do call it pipe,those that are misinformed,I should say.And I am very aware of the hazards of using heat without concern can do,I have been working around iron and steel and have done my share of welding and hot work.Whether wrong or right the tubing would be mildly heated and formed in the field.Fab shops would take a different approach and more than likely cold bend it with a pricey bending machine,which I don't have.On a mild 20 or 40 degree bend is the structural integrity compromised when using just enough heat to make the bend to a degree that it be unsafe?
Reply:Originally Posted by nmaineronWalker, why don't you enlighten me with some of your wisdom so that I may be educated on this matter.I am very aware of what Drawn over Mandrel tubing is,I have already purchased it,some people do call it pipe,those that are misinformed,I should say.And I am very aware of the hazards of using heat without concern can do,I have been working around iron and steel and have done my share of welding and hot work.Whether wrong or right the tubing would be mildly heated and formed in the field.Fab shops would take a different approach and more than likely cold bend it with a pricey bending machine,which I don't have.On a mild 20 or 40 degree bend is the structural integrity compromised when using just enough heat to make the bend to a degree that it be unsafe?
Reply:Thanks Broccoli1, I don't want to get into a pissing contest here and I don't want to throw insults around. My thoughts on this come from the process of building a structure and the general school of thought that goes along with it.I have been working and gathering info on this for awhile and my main issue has been getting my tubing bent.I respect the general opinion that the tubing should be bent cold and if I could afford to buy a bender, which I may do anyway, I would most certainly do it.However,why be so critical of a heated bend where 6" away from that bend will be a weld that will be at a much higher temp and will compromise two pieces of tubing.Ideally you would want the whole frame to be preheated to weld to do it by the book,but I highly doubt that this is followed in very many shops.I will TIG weld this frame in a jig which I have already made,all joints will be coped and none will be completely welded until all joints are tacked.I guess I shouldn't expect much of an answer to a basic question but I am certainly not as basic as my question suggests...
Reply:I guess I don't understand this, you claim you have 4 bends to make, you know what degree of bend you need, so why not just take it to a shop and have them make the bends for you?  You're talking about buying a bender now, so you're either looking at spending $500+ for a tubing bender, or you're planning on spending $100 for a harbor freight pipe bender which will kink it all the same as hand bending.  I don't know about around there, but I know I could get those 4 bends made for less than $50 here.
Reply:I make bends for all kinds of stuff; hot, cold; hand, oneshot, JD^2, etc etc. HREW, CREW and DOM all come as pipe and tube. The terms "pipe" and "tube" have to do with size specs, not manufacture process. those that think "tube" is only structural should try building a hydraulic system using pipe, and those that think pipe is only for fluid movement should try finding scaffolding clamps or chain link fence hardware that fits tube. Sorry for the judgmental postings above, nobody knows what you know but you and that was a fair question. It is my opinion that if anything you are "nuking" it, as in over thinking insignificant details. The only concern is kinking, don't use kinked bends regardless of size or material on anything life dependent. If strength is a concern jump up a size. If using a 10xx series or A3x steel just figure 20k lbs yield strength per 1"^2 cross section. Figure the cross section of your tube by finding area of a circle for outside diameter in inches minus area of a circle for inside diameter in inches and multiply that by 20k. Then figure what are going going to be doing on your motorcycle that will incur that much force, and what the implications would be for the rider. If there's concern at all, jump up a size or find a thicker wall. In short, depending what the 1" pipe/tube is for, I would have no problem hot bending it by hand. Though I have to say I'm not really sure where in a motorcycle frame I'd use 1", other than handlebars. I'd bend handlebars by beating them on sidewalk without concern, so long as they don't kink.
Reply:Antibling, the nearest shop that I found that had the capabilities,cold bending,which is a couple hours away won't do it due to insurance/liability issues.I tried to buy my tubing there and made the mistake of telling them my plans,company policy says no to bending.I live quite rural and I don't know of anyone that has built a frame and I know most everyone that would be inclined to do so.Redone,Thanks and I agree,I should just do what I know how to do.My tubing is actually 1.125 x .0885 which is the same as an old Harley frame that I have.It is generally recommended for the older machines like the one I will be building.
Reply:Since you are in Maine, the first thing that jumps to my mind is ships and fishing rigs.  I would suspect there are some boat repair places that bend 1" stainless for railings etc who would be happy to bend it.  40 degree bends without dies seems destined to create some flat spots on the tubing.  Post pictures as you progress.Miller Syncrowave 350Millermatic 252/ 30A spoolgunMiller Bobcat 225g w/ 3545 spoolgunLincoln PowerArc4000Lincoln 175 Mig  Lincoln 135 Mig Everlast 250EX TigCentury ac/dc 230 amp stickVictor O/AHypertherm 1000 plasma
Reply:I wish it were that easy, the coast is three hours away.
Reply:The biggest issue that I see with heating the metal will be controlling where it bends.  If, for example, the outside of the bend is hotter - it will tend to stretch with the inside being more or less nominal thickness.   so you get a weak spot on the outside.The trick to a good tubing bender is the dies.  JD2 used to say their dies aren't exactly round because they actually pinch the tube a bit to make sure the end result is in fact round.  That kind of precision is hard to come by with a torch.So you have to factor in buying a bender plus the cost of the dies.Better solution - there are lots of places that will bend tubing and stick them in a box and send them to you.  Significant savings in money.   S&W racecars (in PA. I think) used to do this for roll cages.  You send them drawing, they send you parts.As for benders.  I picked up a Hossfeld with a starter set (railings, angle iron, and 1.5" pipe dies) for $500.  I think I got a pretty good deal.  I bought it from a professional shop where the guy was tired of switching dies and looking up on charts which dies to use.  To much hassle for him.  Cost me $40 worth of diesel to pick it up (2hr drive).  So far I got another $100 into a hydraulic conversion (scavanging parts from friends and Craigslist) - need a 2 way control valve.  On top of that I need tubing dies.  Suspect I will be at $1000 when done.Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX