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Question on threading stainless steel

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  • Question on threading stainless steel

    A friend has asked me to make him some roller rods for his boat trailer, used in salt water. Existing are steel and rusting badly. They are 5/8" dia by 15" long, threaded 1" both ends for lock nuts. He wants them from stainless steel, which I can get in either 304 or 316 alloy.

    Which alloy will be the easiest to thread? I will be doing the work on a HF 12 X 36 gear head lathe, with either carbide insert or HSS tools, I have both. I have done some threading, and know what to do. My aprehension is due to a bad experience with 304 stainless work hardening on me, I don't know if 316 will be any better. The 316 is 30% cheaper, so I am looking to use it. My threading technique normally is to cut threads till I am just about there, then use a threading die to get final shape and size.

    Any experience out there? Any comments on work hardening? The source of the rod will be MSC, they list both 304 and 316 for $20 to $30 dollars a 6' piece.


  • #2
    After you thread SS a few times, it's not that bad. For your application, you don't have to worry about the class of fit. Just thread for 5/8-11. Or whatever size you need.Wouldn't worry about the alloy, both will work. If your tool is sharp; as it should be, use HSS.
    Last edited by Millman; 09-02-2006, 11:30 AM.


    • #3
      Question on threading stainless steel


      Given the choice I'd use 316 every time. It machines easily and is more resistant to salt water corrosion. Where I worked for the last 27 years we made all of our mooring components for oceanographic instrument packages from 316 so I can claim a little experience with the stuff. If you want to completely eliminate all corrosion there is a trick I learned. Once your rods are made and threaded, put them in a plastic pan and allow them to soak over night in OSPHO (it is a rust preventative primer available in paint and hardware stores). This stuff is oxyalic and phosphoric acid. It removes any iron residue from the surface of the machined part and passivates the surface. I even used it on contaminated welds to remove the iron. Works like a champ!!!

      Good luck with your project,
      Jim (KB4IVH)

      Only fools abuse their tools.


      • #4
        I have just come up from machining some stainless- dont worry about it , just thread away, its not that bad.

        that ospho tip is going to get used right now as the stainless bits are going overboard tomorrow- thanks I was worrying about staining!


        • #5
          There are taps specifically made for stainless. If you plan to do a lot of tapping it may be to your advantage to purchase them.
          Rob Dee


          • #6
            The main thing with SS is don't plan on taking light cuts of less than a few thou. The tool will skip out of the work and harden it immediately and then you are screwed. Especially when threading do not plan on a fine cleanup skim cut as the last cut. Instead plan the cuts so that the last cut takes off at least several thou or a little more and you should have no trouble.
            Free software for calculating bolt circles and similar: Click Here


            • #7
              Thanks, guys,
              I feel better about it. I knew about cutting and not rubbing, just wasen't sure about 316. That is the cheapest alloy, and I knew it was better at resisting corrosion. I like the idea of passivating the alloy, I'll use that idea.