Mild Steel or Chromemoly Cage?

What is the best way to check for a mild steel or chromemoly cage? Is there a pretty good way to test in the field when looking at chassis's? THANKS, Jim

 

If its Mig welded....definitely not Moly! BUT...I have Mild cages in Door Cars and the Customer wanted Tig welding (for appearance) So ya just cant go by the weld! I also use D.O.M. for Mild...many use E.R.W.....of which you will se a seam....Just tossing some things out there

 

Drill a tiny 1/8 in hole. Mild steel will be around .120 thick. Moly will be a where from .058-.083. And moly drills really hard.

 

THANK YOU for the replies!

It is TIG welded and it is under .080 thick, but wanting to sell the car and just wanted to make sure before I told the person it was CM for sure. It is a 2700# dual frame door car and it had a NHRA 7.50 and slower certification on it and I was worried it was Mild Steel due to the cert. THANKS for the help! Jim

 

That is incorrect, my MW kit car uses .120 wall chrome-moly and it was verified by the NHRA chassis inspector of its availability.

The best way to find out is to cut out a small section and have it analyzed by a metals testing lab.

 

depending on what bar(s) you are referring to, less that .083 for moly is not certifiable. some bars may be .065 and .058 but for all the main outer cage structure it must be .083 or greater

 

buy a Ultrasonic Thickness on ebay

 

Thickness won't tell you if it is the correct material or not. I would load it up and take it to a scrap metal recycle yard. My local yard has a "gun" that they can shoot the tube with and it will tell you the material. It does not give you the carbon content so you cant tell the difference between 1018 and 1022 but it can tell you if it is 4130 or not. You can also buy one of those guns for about $30,000.00 if you like. They may have come down since I first looked at them.

The "gun" also will not tell you the heat treating of the tube. Not that it matters for this discussion but there was a lot of tube coming from Germany that was SR not N. The suppliers were trying to convince you that it was all the same since it met the mil spec.
Jeff

 

41xx

I can generally tell moly from 1018 by spark testing with a high speed grinder. Moly sparks look like a tall palm tree mold looks like some kind of bush. Prolly not useful info for a built chassis.