Hardened Shaft Material

[AlexWestling]

I am designing a set of rockers for my car as a spare time project. My question is what my material of choice should be for the shafts. The shafts will be .500in in diameter and will have needle bearings riding on them so they will need to be hardened.

I was looking at some of the rocker manufactures websites and noticed either 4340 or 8620 steel was used. What is the difference between these two steels.

I know 4340 can be threw hardend and 8620 is case hardened. What will be better as far as stregth/wear? Thanks for any help.

 

[salmon2]

A quick chemistry check can tell you that 8620 got expensive Ni at .4~.7 and .20 Carbon, while 4340 got .40 Caron and 2.0 Ni. Both of them should quench through .5'' bar, but 4340 should have better toughness/strength because of high Ni, but should be more expensive.

 

[unclesyd]

You might want to look at the 60 Case shafts made by Thompson/Danaher. These are precision shafts with very high hardness and excellent surface finish. We used this material for many other applications other than what is normally used for. There is also similar shafts that have a hard chrome plating that make excellent bearing races.

http://www.danahermotion.com/website/com/eng/misc/popup_ps.php