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Need hardness comparison of Rockwell C

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  • Need hardness comparison of Rockwell C

    Why would 4130 only be "hardened" to 30 R-C? I thought this is about Stock hardness. Seller is claiming Hardened. Wut up wit dat? Can someone give a comparison to 30RC? Like how would that compare to say a HSS cutting bit or bearing race? Could it be re-hardned?

    I copied this from another thread so I wouldn't be "hijacking" that thread. Sorry.

  • #2
    30 Rc is pretty standard for "pre-heat treated material"...Its not that hard, and HSS will do just fine with it, although your cutting tool will wear more quickly because of the hardness.. you will achieve a pretty good finish because of the hardness..

    I order 4140 and 4130 pre heatreated on a regular basis, and It machines just fine..You can reheatreat it, no problem...
    But I never use this stuff if I am going to harden it harder...only for stuff that I don't want to harden more...



    • #3
      How hard do you want it? Fully annealed it's something like Rc15. For most applications 30 is hard enough. Bearing races and tool bits are something like Rc62 and brittle as glass.


      • #4
        Thanks guys. I guess I won't be rolling welds with it. The items are English Wheel anvils. The ebay listing(s) say "Hardend to 30-32 Rockwell C". This just seemed SOFT to me.

        I made a Q&D E-Wheel using bearings and it works great for small items. Just looking to fab something larger.


        • #5
          We use to buy forgings soft at 20 to 22, or hardened to Rc 29-30. This is the ideal hardness for machining/polishing.
          If you are worried about marring,etc, consider having it gas nitrited, and it will be 60-62 with a 28-30 base structure.
          Or, you may want to consider going to 4340 and you will get it at 38-40 Rc