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  • Tapping Stainless Steel



    I need drill and tap some holes in stainless steel. I'm planning on using cobalt bits for the drilling, but can't find cobalt taps. Does anyone make a cobalt tap or does anyone have a suggestion on what tap to use?

  • #2
    No suggestions as to which tap, just take it reeeeaaaaallll easy.
    Back off and clear swarf with compressed air, every 1/4 turn, if it seems sticky. Any lube will help, of course, but I find Tap-Magic works better than most (and it smells wunnerful when hot )
    Just got my head together
    now my body's falling apart

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    • #3
      What size holes?
      Do you have a large number to do. If so:

      Use the largest allowable TDS* drills (HHS with coolant work great) for the tap you are using . 55 % thread is ok
      Use only taps that are made for stainless.
      The "black coated" ones work well.
      Use lots of cutting oil.
      Do not let your work get hot....

      *check machinery hand book
      please visit my webpage:
      http://motorworks88.webs.com/

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      • #4
        working stainless

        harley:
        Stainless in not hard to work but you must work with care. It willl work harden. Keep drills sharp. Use a proper speed, too fast will slow things down and cause problems. Use a gun tap spiral flute or spiral point even for hand tapping. use cutting fluid for tough metals. when I worked at the boat yard they bought Anchor lube by the gallon. They did a lot of SS railing fabrication. Anchor lube is non toxic and approved by USDA for food service work. Castrol moly D is also a good tapping fluid for tough metals.

        reminds me I worked R&D for a yacth buider one of the woodchucks (The metal shops name for cabinet makers) asked to borrow my drill index. He was drilling stainless he ruined a half a dozen bits before i realized what he was doing he obviously did not know what he was doing. You cant treat stainless like wood or aluminum.
        Regards
        Tin
        Ad maiorem dei gloriam - Ad vitam paramus

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        • #5
          Anchor Lube is excellent !
          Do 50 to 55 % thread percentage for tap drill
          Get OSG "Exo Taps

          No Problemo's
          Rich

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          • #6
            What kkind of stainless?

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            • #7
              1/4-20 H3 PLG CLEVELAND HIGH SPEED STEEL FAST SPIRAL FLUTE TAP
              Thread Size: 1/4-20
              Material: HSS
              Chamfer Style: Plug
              Ground Thread Limit: H3
              Number of Flutes: 3
              Overall Length (Inch): 2-1/2
              Manufacturer Part Number: C58562

              Will that do the job with copious quantities of Tap Magic?
              I can't find anything but HSS taps.

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              • #8
                Originally posted by Rich Carlstedt
                Anchor Lube is excellent !
                Do 50 to 55 % thread percentage for tap drill
                Get OSG "Exo Taps

                No Problemo's
                Rich
                Rich Has an Excelent suggestion here. Unless this is a one time thing with one or two holes get the right tools for the job ie a tap made for tough stuff with the propper coating and a cutting fluid for tough metals. A good cutting fluid reduces the torque required to turn the tap this in turn gives you better feel and reduces the chance of breaking a tap.
                Regards
                Tin
                Ad maiorem dei gloriam - Ad vitam paramus

                Comment


                • #9
                  I do that kind of tapping with HSS all the time in 300 series SS. As suggested, the thread percentage is the most critical. Once you're in that 50-60% range it should be pretty easy. A frequent job is a 10-32 in 3/8" 303, for which I use a #19 for 59%, a 3 flute HSS plug tap with Tapmatic Natural, and a tapping head. Never a problem.
                  Location: Jersey City NJ USA

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                  • #10
                    Greenfield EM taps are tops IMHO,you need the Rc hardness of the material you are using to select the correct series.They will allow you 65% threads in most 300-400 series SS.

                    One note,with these you don't break the chip with every turn like a hand tap.These you just power it in,the chip comes out the back like those from a drill.
                    I just need one more tool,just one!

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                    • #11
                      Be aware that the two weakest threads for tapping are 8-24 and 1/4-20.
                      That means that they have the smallest root diameter,divided by the major diameter, so the root of the tap sees a larger than normal load...therefore making these two sizes, the easiest to fail.

                      Rich

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