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  • Broken tap

    Thought I'd try my hand at Rudy's "Radial Five", now that the article is finally complete. All going great till I tapped a hole in the back of the valve chamber and, damn!, broke the 2-56 tap in the hole. I've heard the tap could be dissolved out somehow. How ? It's a regular steel tap stuck in aluminum. Alum? Vinegar? Suggestions? TIA
    Bob

  • #2
    Here are some old threads that disscuss that issue, they might be of some help. Good luck.I usually use a 2 flute solid carbide endmill in the milling machine to cut the tap away.

    Mike

    http://bbs.homeshopmachinist.net//Fo...ML/004016.html

    http://bbs.homeshopmachinist.net//Fo...ML/003776.html

    http://bbs.homeshopmachinist.net//Fo...ML/002117.html

    http://bbs.homeshopmachinist.net//Fo...ML/001596.html


    [This message has been edited by coles-webb (edited 05-22-2004).]

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    • #3
      Thanks, guys. Most helpful.

      Comment


      • #4
        Had the same problem many times. Nitric will eat the tap but not the aluminum. This is how we saved alot of high dollar defense parts from the scrap pile, so I know it works well. Good luck

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        • #5
          CW,
          endmill to cut out the tap? really?
          my time in the shop today was cut short
          due to a broken tap ... M8! .. there's probably a 1/4" of it still in the hole.

          it was a long morning.. had to walk away.. figure i'd try to dig it out tomorrow.

          any tips? i have a small (1/8"?) 2flute.. i'd guess i'd just burn the endmill, no?

          -tony

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          • #6
            Yes I have used 1/8 and even a 1/16 solid carbide center cutting endmill to cut out a HSS tap. It needs to be done on a rigid machine(I did do one once on a drill press to remove a broken easy-out stuck in a brake bleeder screw). The Carbide is harder than the HSS. Put the piece in the vise or clamp to a milling table. I don't usually use any coolent other than a light oil and some compressed air to blow the chips away. You don't need the carbide end mill going that fast (400 to 700 RPM) and slowly eat away at the center of the broken tap using a fine feed. Once you are 1/2 to 3/4 of the way through the tap you can usually use a prick punch(not a center punch) to break away the left over pieces of tap(sometimes a quick tap with a pin punch, 1/16, in the center will also break it out). If the tap is much larger than the solid carbide end mill ensure you go down the center but off to one side. As long as you make full contact with the broken tap as the solid carbide end mill is hard but brittle and will sometimes break if you make an interupted cut. Go slowly and blow the chips away frequently as they can cause problems if left in the hole(kinda of like drilling with gravel in the hole). If the solid carbide end mill chips thats ok as you can keep going if its still cutting or sharpen by hand as accuacy isn't the issue at this point. You can also use a solid carbide burr in a die grinder(regular or pencil style) if the peice is to large to put in the mill, but it will take longer as a burr cuts slower(I once spent 2 hours removing a 1/4-28 tap broken off in a jet engine). I save all pieces of broken carbide cutter for this purpose as they can be sharpened by hand(even old TIG welding electrodes). I've never tried the nitric acid as it's not something we have at work and someone usually wants the piece fairly quick. Let me know how you make out.

            Mike

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