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2" Pipe Tap In Stainless

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  • 2" Pipe Tap In Stainless

    Welded a "weld O let" to a piece of pipe and had to chase out the threads for a 2" nipple. What a work out, got the tap seated to the bottom threads with a 12" wrench no problem. I start the cut, dead in the water. Add tapping fluid and a 14" wrench get 1/2 turn, back cuttings out and try again, no dice. Get the 24" wrench and get super secret tap stick, add 225 pounds of fat guy (me) and get 3/4 turn. Now I am not happy all I want to do is chase out said threads(the weld o let was oval). I put a 6' pipe on my 24" Armstrong adjustable and have at it. This thing is smoking from the torque I am inflicting as my helper laughs holding the wrench. Once again 1/2 turn and back cuttings out. To make a long story short we got the job done, did not shatter the tap, and are damn glad we did this project in the shop. Cutting threads on a 300 are one thing tapping 2" SS is another.

  • #2
    Re: 2" Pipe Tap In Stainless

    How did it oval?
    From the weld?

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    • #3
      Re: 2" Pipe Tap In Stainless

      We had a nipple screwed all the way in when we welded it and ran as cool as possible, think it was an imported fitting. Must have done this hundreds of times, never had one that bad. Usually you just run the tap in by hand to chase out the threads.

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      • #4
        Re: 2" Pipe Tap In Stainless

        With the imported fittings, you never know what was in the "Stainless". Some forms of stainless are heat treatable, sounds like you inadvertently hardened it. Even 300 series stainless, which every metallurgy book will tell you is non hardenable, will get hard as hell if your drill bit craps and begins glowing halfway thru the hole. If it is blue when you pull the bit out, get the carbide out!

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        • #5
          Re: 2" Pipe Tap In Stainless

          316 hardens up like a rock, 304 usually stays workable, this was all 304. Like you said with the import crap who knows what it really is.

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          • #6
            Re: 2" Pipe Tap In Stainless

            I don't know what you were using for tapping fluid but my experience (and lots of it) with tapping stainless has taught me this--if you can't find the Ridgid dark threading oil then used auto motor oil works really well. We used to use the stuff they brought in to fuel our boilers, something called "bunker C", thick as molasses but a great cutting oil. This is also dictated by what the fabbed piping is to be and how you can clean it. Good Luck, David

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            • #7
              Re: 2" Pipe Tap In Stainless

              If the nipple wasn't from a dependable maufacturer, then you risk 2 things!
              1. the nipple wasn't 2", but 50, or 51mm Metric, as used over here!
              2. If the alloy isn't propper standard, but out of proportion, ie, less Chrome than there should be, compensated by extra nikkel, then the metal becomes unusually difficult to work in.
              With Tozzi's experience in stainless, I bet he notices the difference during Tig welding too!
              It's reasonable to expect that the next (good & correct) job can be turned out by hand, as Tozzi expected.
              Happy Easter Guys!

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              • #8
                Re: 2" Pipe Tap In Stainless

                I use Tap Magic for most stuff or "stick wax", both are made for machining all metals.

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                • #9
                  Re: 2" Pipe Tap In Stainless

                  Hi Stainless Master, Welcome. We could also use Your advice over here.

                  http:/www.hobartwelders.com/weldtalk

                  There is a stainless section,great members Toolaholic , there also
                  I can build anything You want , if you draw a picture of it , on the back of a big enough check .

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                  • #10
                    Re: 2" Pipe Tap In Stainless

                    I fabricated 1000 stainless pipe welds for the Mazda plant in 1985 for Hoyt Brumm and Link, a mechanical contractor in Detroit area. In doing so I had to weld into holes drilled by others, couplings and weld-o-lets. I found the same problem as you found. If you screw a nipple into the coupeling inorder to square and level it up during tack up----you better screw it out before welding or else she will not come out. You claimed to have "done this a hundred times before and a tap worked ok " I am here to tell you that to make a mistake is easy, but to continualy make a mistake such as having to tap a thread because you leave the nipple in during welding is insane. Why not remove the nipple or just screw it in one thread to protect the threads? As far as the Foreign fitting or wrong tap fluid thoughts found here ....Motown

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