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How to remove stripped hardened set screws?

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  • How to remove stripped hardened set screws?

    I recently acquired a very large woodworking jointer and the cutterhead has allen head set screws and 5 of them have been stripped. I've ordered some new ones and while I am waiting for them to arrive I figured I would try to remove the old ones. There isn't a lot of material left on the stripped ones so I figured I would drill a smaller hole deeper into the screw and use this for the remover to grab on to. When I went to drill them the bit wouldn't touch them. Perhaps I should have figured they were hardened but now I'm at a loss as to how I can remove them. Any advice or ideas?

  • #2
    A dental diamond bur can be used to make screwdriver slots. It'll work better in a high speed handpiece.

    Do dentists in CA make house calls?

    Another method (much more tricky one) is to weld extensions to the broken screws. But you need to know exactly what you're doing.
    Last edited by MichaelP; 10-13-2010, 11:57 AM.
    WI/IL border, USA


    • #3
      Get a screwdriver bit set that has plenty of sizes and shapes(Hex, splines,torx). Select one that is too big and hammer it in.

      The rest you know
      " you not think you have enough machines?"


      • #4
        My first thought is you're drill bit didn't start good because it was on a damaged surface--not flat. I've had this before when trying to remove buggered screws. Start with a proper spotting drill and go in enough to make a good start for your drill point to engage.

        Uneven surfaces on small drills can have the effect of snapping a flute edge and then you just RUB. It can sure feel like you're drilling into something unable to be cut!


        • #5
          I had thought about the screwdriver as I have a lot of extras to try out. Heck I could grind one to fit if need be. There may be just enough bite to get it out. The diamond bit method will probably be next. Since it's an allen head the base isn't really blemished but mostly the sides. I tried a couple different bits and doubled checked sharpness to make sure it wasn't the bit. Good ideas to start with.


          • #6
            Can you post a pic of the cutterhead, showing the gibs?

            I'm thinking that if you have access to the business end of the allen screw...where it pushes on the gib, perhaps you could use a thin cutoff wheel to grind away the end and relieve the pressure on the screw and loosen it.


            • #7
              One other, more traditional, idea is a stub screw-extractor. Those are particularly good for allen head screws because you already have the hole to grab, the problem is your extractor bottoms out before it can.
              The Shallow-Grip ones listed here are an example:
              Or make your own by grinding off the end of the extractor you already tried.
              Last edited by Arthur.Marks; 10-13-2010, 12:41 PM.


              • #8
                We faced this over 40 yrs ago in Britain ----

                and found that the set screws could be drilled only with Dormer brand drills, all the rest failed to make any impression. perhaps you might try some top quality hss drills, and if they dont work then move on to carbide drills, but mind you do not break any carbide ones off !!! Regards David Powell.


                • #9
                  I recently drilled out a broken off HSS tap with an Omegadrill bit.


                  This just one size for illustration, they come in about 5 or 6 different sizes.
                  It went through the tap like butter. The cutting edges have a negative rake which makes them very tough. Run at about 2000 RPM, dry.

                  Kind of expensive, but they work.



                  • #10
                    A left hand cobalt drill bit may sometimes work; either alone or in combination with one of the removal methods noted above.

                    Are these blind (not through) tapped holes? If so, some of the methods like the Omega drill (generally good) may be a bit harder to use -- you won't be able to punch the bits of remaining set screw through the hole.


                    • #11
                      Originally posted by RWO
                      I recently drilled out a broken off HSS tap with an Omegadrill bit.

                      It went through the tap like butter.
                      How much feed pressure is required with carbide drills like the Omegadrill ?



                      • #12
                        A new or sharpened carbide tipped drill for masonry will drill hard material. A couple of dollars at the hardware store. I might sharpen one left handed and see if it would grab and twist the screw out. If it's deep you'd have to blow the chips out once in a while since the flutes would be backward.

                        Good luck.


                        • #13
                          Use a carbide spade drill. They are cheap and tough. They come in a lot of sizes. They will drill hardened tool steel (like taps) so a set screw is nothing.
                          Kansas City area


                          • #14
                            Here are some pictures. It's a 16 inch cutterhead and each set screw is 3/8" x 16 x 1.5". I tried using a mason bit after sharpenig one up and it cuts. Trouble is I don't have an extractor the right size. I would consider drilling it out all the way but at 1.5" long it's hard to tell if I'm going straight enough. Hopefully I can get a good extractor soon that fits and get them loose. As is the machine works and cuts good although once the blades are sharpened it should do great.

                            Last edited by Dale Lusby; 10-13-2010, 08:36 PM.


                            • #15
                              For a quick & dirty screw extractor, take a worn out or broken tap a bit over the hole diameter, break/cut off the fluted section, and grind it into a slightly tapered square section. Using your 2 oz. ball peen hammer, tap it into the drilled hole, attach a tap handle and turn the set screw out. Almost takes as much time to tell how I do it, as to do it!

                              David Kaiser
                              “You can have peace. Or you can have freedom. Don't ever count on having both at once.”
                              ― Robert A. Heinlein