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Can you guys settle this..alum annealing...

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  • Can you guys settle this..alum annealing...

    Cast aluminum motorcycle heads....what is a maximum safe temperature to heat them to for pressing in guides or valve seats? I'm told 350 degrees F will permanently destroy them, yet in operation, these things are running @ about 330 deg. Can the gurus settle this? Thanks!

  • #2
    When I worked in aircaft repair the basic rule for heating alloy aluminum was no hotter than boiling water. That is always a safe temperature and it is very easy to control.
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    • #3
      They run hotter but they're also bolted down. Free heating can warp a head and it doesn't take much. I prefer to freeze the guides to install.


      • #4
        Destruction by overheating depends on type of Alloy 6061 etc. an what it does is ruin the temper. I've used BOTH the replies, heat the alloy in hot water AND use a pre-freezed guide, but yer got to be quick. for fitting seats you need to freeze a bit deeper, Liquid NITROGEN, cos yer fridge don't go down there.
        Regards Ian.
        You might not like what I say,but that doesn't mean I'm wrong.


        • #5
          Dry ice?

          Will "dry ice" work as well?


          • #6
            i have used dry ice and Wow does it ever work. Don't touch it with your hands. I figure you will have about 30 seconds to fit everything it, if you heat with water and cool with dry ice.



            • #7
              When using dry ice make a bath of it using acetone. This will allow much quicker cooling and makes it possible to re-cool a part by pouring some of the acetone on the part. Of course, acetone is extemely flammable at room temperature so use accordingly and with plenty of ventilation. The mixture of dry ice and acetone produces a liquid at a temperature just above the freezing point of acetone at about -90F. It's a good substitute for liquid nitrogen.

              BTW, if you heat with water and use cryogenic freezing make sure you give the water time to evaporate from the hot part or the cold part will freeze it. Ice is a remarkable glue and will bring the operation to a halt.
              Last edited by Evan; 06-23-2008, 09:26 AM.
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