Tips for distinguishing mild steel from chromoly chassis?

[ricardo1967]

Hi guys,

I'm looking for tips on how to distinguish chassis parts (e.g. tubing) made of mild steel and 4130 CrMo.

I'm convinced my 173" FED (late 60's/early 70's era, believed to be a SPE chassis) is plain mild steel but I wouldn't mind knowing for sure.

2nd question:
Let's say my chassis is mild steel and it needs a front-half... would it make sense the front-half with CroMo? Weight wise, it probably doesn't, because being a vintage FED the engine isn't very far out and it requires a heavy front end to keep the front tires on the ground.

PS.: The car is currently not SFI tagged, but I consider it an option in the future.

Thanks as always. I'm so grateful for you guys taking a break from the fab shop to share your wisdom here.

[dreracecar]

There is destructive and non-destructive
Sonic is non -destructive, drilling holes to determine wall thickness is
moly cars are much thinner wall than mild steel unless the builder used muffler tubing.
Tapping a steel rod on moly will ring whereas mild will thud, test on both to hear the tone.
Moly comes in presise(real close at least) wall thickness .049-.058-.065-.083-.095-.120 for the sizes we use, mild steel wall thickness's do not match any of these numbers so any different from the moly numbers, good bet that its mild

[rooman]

This is a bit subjective and it would pay to get your baseline from some identifiable tubing so you know what to look for. Then there is the question of where to grind where it is not going to screw up the frame. Bruce's suggestion may be better.

http://www.capeforge.com/Spark%20testing.html

Roo

[30dodgeboy]

A couple of the larger scrap processor yards around here have these Niton (spelling?) guns that zap a small spot of the clean metal and then look at the spectrum emitted to identify exactly what the material is made of and what percentages.  If any chromium shows up in your case, then you have your answer.  Perhaps a bigger scrap metal processor in your area has one.

[PSweeney]

if you can stomach the cost of moly over mild, use moly and add weight over the axle where it's needed.

[dreracecar]

I dont think that Roy Fajasted (SPE)would build a dragster out of mild steel

[JoydayVox]

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