Topic: DOM tubing vs ERW tubing

[Gearhead Wiki]

Does anyone know the difference between DOM tubing and ERW tubing.  I know that DOM is ERW tubing that is "reworked" and that DOM is stronger and more expensive but does anyone know, for example, How much stronger?

[To The Floor]

well dom stands for drawn over mandrel meaning it is seamless tubing.  hrew is rolled over and welded at a seam.  so dom is stronger being one solid piece.  you also have to think that the smaller the tubing, the less it will dent because there is less area inside the tubing for it to push in, and a smaller diameter means the tube is a tigher overall circumference which makes it stronger.  also wall thickness comes into play.  i use 1 5/8" dom, because it's unique and no one uses it.  but i'd say use 1.5" dom with a .120 wall for toyotas, and heavier full size rigs (dodge chev ford) i'd use 1.75" dom with a .156 or .188 wall tubing.

[waskillywabbit]

well dom stands for drawn over mandrel meaning it is seamless tubing.  hrew is rolled over and welded at a seam.  so dom is stronger being one solid piece.  you also have to think that the smaller the tubing, the less it will dent because there is less area inside the tubing for it to push in, and a smaller diameter means the tube is a tigher overall circumference which makes it stronger.  also wall thickness comes into play.  i use 1 5/8" dom, because it's unique and no one uses it.  but i'd say use 1.5" dom with a .120 wall for toyotas, and heavier full size rigs (dodge chev ford) i'd use 1.75" dom with a .156 or .188 wall tubing.

Not exactly correct in your assessment of DOM tubing, as it is a popular misconception that DOM is not welded, when in fact, it IS is welded.  From http://www.steeltubeinstitute.org/dom.htm as it is explained there well.

"The manufacturing process for DOM tubing begins with coils of steel, which are slit to the proper width for the desired tube size. The strip is cold formed and passed through an electric resistance welder which joins the edges together, under pressure, to complete the tubular shape. After testing the weld's integrity, the tubing is cut to length for further processing.

The cold-drawing process creates a uniform, precision product with substantially improved tolerances, surface finish and tensile strength, increased hardness and good machinability. In this process, the tube is cleaned and annealed, and one end of each length is squeezed to a point so it can be gripped by the drawing mechanism. The tube is then drawn through one or more dies and over mandrels. This reduces the diameter of the tube and thins its walls to the required dimensions in a controlled fashion to provide the qualities desired in the finished product. Metallurgically, drawing improves the tube's concentricity, tensile strength, hardness and machinability. Close dimensional accuracy is achieved through tight control of both outside and inside diameters."

And I'll let you read the various stuff about ERW for yourself... http://www.steeltubeinstitute.org/hss.htm

I'm going to use 1.75" DOM 0.120" wall for my exo.  Properly triangulated and braced, it'll be rock solid.

[freds40]

Not sure on actual numbers comparing the strength, but if you have bent both on a manual bender, your arms will sure tell ya DOM is stronger.

[Gearhead Wiki [OP]]

Does any one know the numbers of how much stronger it is?

[snow runner]

Does this mean, for a traffic situation, if struck from behind the ERW would give a little more and absorb some impact?  there by possibly not pushing one intot he vehicle in front of it?

[Gearhead Wiki [OP]]

I was thinking more of trail situations.  like which would be better for a roll bar and bumpers. I know that DOM would be better but I am not that hardcore so for the extra cost im not sure that DOM would be needed.

[pumkin toy]

i just graduated from wytech about 6 months ago. i took the chassis fab class in which we learned how to build all sorts of roll cages and linked suspension systems. it was based around building race cars but same rules apply to all roll cages. i built an exo cage on my toy while i was in that class. i told them i did'nt have the money for DOM or chromoly tubing, and they suggested that i use 1" 5/8" x .120 wall HREW (hot rolled electric weld). basically it's regular welded seam tubing. nothing special. they said that it would be plenty strong if built properly, and they are VERY STRICT on rules and strength of build so i would say that DOM probably is'nt necessary.

[Gearhead Wiki [OP]]

Thanx. I think that as long as you're not using some sort of crap thinwall tubing it should be good

[snow runner]

thank you also. I just ordered the ERW tubing hopefully it won't take too long.