6061 T6 vs 4140 CM for rear upper control arm adjusters, are they equally strong?

[Nicks67GTO]

So iv'e been doing some looking at what it will take to make my 68-72 RUCA's work in my 67' GTO. Its no big deal, i just need 2.5" extra in the middle coupling to make this happen. I might have a deal with QA1 where they'll just sell me the part and be done with it. Anyhow this has led me to start looking at materials used in the adjusters. Iv'e found that some shops are running 6061 T6 Aluminum for the adjusters and some guys are running 4140 Chromoly.

Are they really equal in strength? I just have a hard time wrapping my mind around aluminum being as strong as steel.

[Nicks67GTO]

Another question, will cold rolled steel function just fine as an adjuster? Its cheap, easy to use and readily available, I was looking up tensile strengths of material and cold rolled is stronger than aluminum in that category, with 4140 being twice as strong as cold rolled steel. Is 4140 just overkill? Anyone?

[Bryce]

Material_____________________________________Tensi le strength at yield

Mild Steel 1018: ______________________________55,100

6061-T6: ____________________________________40,000ksi
7075-T651: __________________________________71,000ksi

4140 (oil quenched at 1200*F and tempered): ______115,000ksi

The other considereation is that steel is 3 times stiffer than aluminum and 3 time the weight.

I build almost everything out of aluminum, the part needs to be design for the material used. You can just change the material, the geometry needs to change as well.

lets compare 1018 to 6061-T6
If you double the wall thickness for the aluminum part then it is 60% stronger than the steel part and still 33% lighter.

[funcars]

DOM tubing is typically a bit better than hot rolled steel and runs about 70-75 ksi and 4130 is typically about 100 ksi normalized. All the various types of aluminum and steel have their place depending on the application and what properties are most important.

[chevelletiger]

make them out of 1018 cr hex.have you machined or tapped 4140 before? theres more tool wear and possibility of breaking a 25.00 to 30.00 tap left and right.i have both sizes of those tap to make stuff like this,the arms im currently working on have a 1"-14 threaded tube bung(1018)and is super overkill.just make sure you do all of you drilling in a lathe let the part cool before you tap it or the threads will be oversized.ask me how i know! lmao! phil