Mild steel cage material.
 

We are using mild steel tubing in a Super Gas car.

We need to buy a few more sticks of tubing.

The roll cage material currently is 1 5/8" EWS. from S&W.

Can we use DOM with the EWS material?

What is the real difference between the two materials?

Thank You for the help.

Re: Mild steel cage material.
 

DOM is DRAWN OVER MANDREL so there is no seam line inside of the tubing. EWS is just standard mild steel tubing the only advantage of the DOM is the more exact Inner diameter. DOM is more expensive than EWS.
I Personally would give S&W call and ask them.
Since your roll cage will be ultra sonic thickness tested, I would consider going up one wall thickness size from the minimum required.
Tubing as manufactured has a tolerance .120 wall tubing may be .118-.122 an it can get even thinner on the outside of a bend.
While slightly thicker tubing is a little heavyer it can be a huge PITA to change out a tube in a completed roll cage. :)

Re: Mild steel cage material.
 

If you can tig weld the cage for the same amount of money you can use 4130 chromoley an you will not add as much weight.

Re: Mild steel cage material.
 

DOM currently runs almost the same price as Chromemoly.
The problem with DOM is the NHRA .118" min spec does not allow for the inconsistency that occurs in wall thickness.
I've had some check as thin as .116 ,Thats why the chassis shops prefer to sell you ERW .134 wall, it will always pass.
IF you have a TIG , I'd use .083 moly . It is permissable to mix mild and moly, but it must be TIG'd.
Always a good idea to save a sample for the chassis inspector to compare to when mixing any of the above.