Broken Set Screw!! Please Help!!
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  1. #1
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    Unhappy Broken Set Screw!! Please Help!!

    Today I was running the Mazak Turning Center and I accidentally restarted program on the wrong process and crashed an allied spade drill into the face of the part, thus breaking the drill. I was able to salvage the part but now the drill is stuck in the turret. To make matters worse I broke the set screw while trying to remove it. Now there is a chunk in there stuck and no allen wrench fits the broken part. I can't remove the tool until I get that set screw out. I thought about drilling through it with a carbide drill but my fear is that I'll ruin the threads on the turret. Any suggestions??

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    Any pictures?

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    no, I'm home now. My supervisor told me to leave it until tomorrow and my guess is the first shift guys will have it out by the time I get there for 2nd shift. But just in case I'd like to know how to get it out. Would an extractor work? The screw broke off at a hollow point so there is the shape of an allen wrench in there, but no allen fits it. I was thinking if I could find an extractor that was close in size I could use that and a tap wrench to back it out but I've never done that before so idk.

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    I've had good luck doing this:

    Grind the nearest oversize Allen key to fit, with a little taper. Dip it into CA (super glue) and put it into the stripped screw. Make sure none of the glue gets the exposed threads.

    Let it cure. Say a prayer. Clamp part so it does not move at all. Use perfect wrench-fu and break screw loose.

    If this does not work, a carbide end mill will

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    thanks, hopefully its fixed by the time I get there but if not I will try this for sure.

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    Just drill it out about .010 under minor diameter.Cobalt drill,not carbide.

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    Right, no carbide tools, you must attack slow with tough metal, by hand, no motor drill. Extractor is a good idea.
    The set screw is soft but the tapered block may be hard, so no chance of repairing the thread if you damage it.

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    Default Re: Broken Set Screw!! Please Help!!

    You might try knocking the stuck drill body the opposite direction it was forced in a little to possibly relieve some of the pressure. If you can. This might make it easier to get the set screw out.

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    I would start with a left handed drill bit. Saved my butt more than once!

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    Just to make sure everyone understands the position I'm in... the screw I'm trying to remove is a set screw that goes into the hole in the turret and pushes against the flat of the tool holder. The set screw is tightened against the flat with an allen wrench. When the tool broke it somehow made that set screw super friggin' tight. When I went to loosen the set screw so I could get the broken tool out, the screw broke about 3/4 of the way down. All that's left in there is a hollowed out set screw which is rock solid tight in there. The hollowed out part is large enough that there isn't much left of it and if I drill it out, I run the chance of messing up the threaded hole in the turret. I'm sure some of you are familiar with these types of set screws, they are threaded on the outside and towards the bottom they have a slightly smaller dia un-threaded portion which is the part that actually pushed into the flat of the tool holder. I may have to bite the bullet and try drilling it out slightly, then trying to remove it with an extractor and tap wrench. Does this seem like the best course of action?

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    86-13c.jpg
    This is the tool holder style, the collet and drill are still inside

    ssfulldog.jpg
    This is the type of set screw

    2_v8_turret.jpg
    The set screw is stuck in the turret

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    Default Re: Broken Set Screw!! Please Help!!

    What you're calling a collet, I call a bushing. You should be able to unbolt the toolholder from the turret. Take it over to a manual mill, chuck it up in a vice and drill it out. You have a better setup this way to drill on location and parallel to the threaded hole. That is how I would do it.

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    Procure the appropriate sized center punch place it against the flattest portion of busted screw tap left with hammer. Usually works, one reason I put anti seize on fasteners on tooling. Plan B TIG weld something you can get a wrench on to it.
    I have found left handed drill bits and extractors frustrating and in-effective you most often will then have a broken screw and broken extractor in there. Not to mention you would have to use a hand drill with a left bit, and it is difficult enough to keep the drill centered even when the broken fastener is held in a vise, let alone free handing it.
    That is a mighty expensive chuck ( I need not tell you ) but if you feel comfortable apply some heat and few brass hammer taps first all around affected area before any of the above or below. I'm not sure if would do this personally with out placing my hands and eyes on it first but it might help. If none of the above work I'll be thinking about this one today and I some other tricks too so ya come up dry, feel free to pm me. Just remember the physicians motto due no harm.
    Best of luck.

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    Procure the appropriate sized center punch place it against the flattest portion of busted screw tap left with hammer. Usually works, one reason I put anti seize on fasteners on tooling. Plan B TIG weld something you can get a wrench on to it.
    I have found left handed drill bits and extractors frustrating and in-effective you most often will then have a broken screw and broken extractor in there. Not to mention you would have to use a hand drill with a left bit, and it is difficult enough to keep the drill centered even when the broken fastener is held in a vise, let alone free handing it.
    That is a mighty expensive chuck ( I need not tell you ) but if you feel comfortable apply some heat and few brass hammer taps first all around affected area before any of the above or below. I'm not sure if would do this personally with out placing my hands and eyes on it first but it might help. If none of the above work I'll be thinking about this one today and I some other tricks too so ya come up dry, feel free to pm me. Just remember the physicians motto due no harm.
    Best of luck.

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    I secound pull the block off the turret. A Bridgeport will see that screw removed in sub 2 minutes. If its that tight your never going to remove it with any kinda extractor.

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    If you can mill a small slot on the top of set screw and use a screw driver

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    I am all for the center punch or small chisel method. You don't care about the screw at this point, and you would be amazed what a shot filled ball peen and a punch can do. I have removed screws (real son of a bitch screws) from holes which you never would have believed that you could be successful with. A few love taps is all it takes to break them loose some times. Once they are loose, you can keep chiseling them around, or if you can break it free without destroying the driver completely, put a wrench on it and spin it out. Set screws are a pita, but yours should be plenty pig enough that it should come right out.

    Husker

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    So the problem is in an ID tool block that bolts to the turret? What's the big problem? Unbolt the block and drill it out in a manual mill and get back to work.

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    If the super said leave it then do just that. Other wise you could be blamed for even more.

    We made special Allen wrenches from used taps with grinding a hex a few thousandth large than a Allen wrench so with a light hammer tap into the over size (washed out) hex the larger wrench would lock in and turn it with ease. You can make them on a surface grinder or even better on a T/C grinder with an index and workhead

    For your problem you could:
    Drill a hole with slow RPM and a sharp drill (so you won’t work harden the broken set screw) with the drill-out drill being about the same size as the Allen wrench . I like to use a good quality cobalt HS drill for less chance of having carbide stuck in a hole. (I feel the same about hard easy-outs as often they can get stuck and become a bigger broblem than first had, and I also drill through when using them.)

    When the drill-out drill gets "all the way" through the bad set screw there is so little screw point holding (if any) that the stuck drill may pull out by hand or hold stuck drill with a vise grip and tap out with a soft (lead) hammer.

    If the stuck drill doesn’t want to pull with a reasonable lead hammer tap then:

    After the drill-out drill bumps the stuck drill you can also bump the drill-out drill point on a grinder to make it a flat bottom drill to get the entire set screw point off the stuck drill. Then re-point the drill–out drill when the job is done.

    To make the flat bottom drill Just bump the drill flat by hand (and test with hand square) or better set in a v-block to bump the side (front face) of surface grinder wheel then back it off on the bench grinder to look like a center cutting end mill grinding just up to the edge made by bumping it flat and then split the center at a slight positive rake (or flat rake is OK) to come close to center with one flute.

    The bad set screw with now having a hole through with no pressure and no damage will turn out easy so no damage will be to your turret thread.

    Another trick is when something is broken off in a threaded hole and you fear to try to start a drill in the in-the–hole stub. For this I drill out the center if a set screw all the way through with leaving the hex not drilled out. Screw the now drill bushing made out of a set screw up to the stub. With that bushing in place I can start a hole or pilot hole at center. The Allen hex still in place makes removal of the temporary bushing easy.


    Buck
    Last edited by michiganbuck; 09-05-2013 at 07:11 PM. Reason: Added "all the way"

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  28. #20
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    Is the shop the kind of place where you can go in off-the-clock to take your lumps, but also see how "first shift" deals with this kind of thing? Might be good to put in an appearance...

    Chip


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