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Excello Mill/Removing Hardened Dowel Pins

Our shop's excello style 602 mill has a problem that I need some help solving. We bought the machine recently and just got it hooked up electrical-wise and started working with it. We noticed that the quill spring was broken and when we opened up the housing the spring was missing. We took out the hub and got another spring from excello. When we went to install the new spring, we noticed that the 3/16" hardened dowel pin that the end of the spring normally hooks around is completely sheared off. The hole is not a through hole (it would go into the quill area) but we were able to push the remains of the pin into the back of the hole. We tried using an extractor set but the hardened steel is hardly dented by the drill bit. There is about 5/16" of open hole that we can insert a new pin. We milled some slots into the cover plate to hold the spring so permanence isn't an issue. Here are our questions:

  1. Is there a drill bit that can drill this hardened pin to use an extractor to pull it out and insert a new pin?

  1. Failing removing the pin, what kind of temporary replacement would hold the load of the very powerful spring. We only need it for a few minutes but this an issue where personal safety could be in danger. We were considering a roll pin or even the shaft of a 3/16" drill bit cut to the right size.

  2. Has anyone had this problem before, more the removing a hardened pin issue rather than the quill spring issue?

Thanks in advance, woodworker88 Los Altos High School Robotics Team Los Altos, CA

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Reply to
woodworker88
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--Not totally clear on the picture but if possible I'd grind the sheared-off flush and drill a new hole somewhere else for a new dowel pin.

Reply to
steamer

Is it is kind of loose and would come out if you could get a good yank on it? If so, you could start an arc on it with a TIG, then bury the tungsten into the puddle. Let it cool and pull it out with your electrode. Probably need to let it cool until the pin is the same temp as the casting, or it will be oversize and that much more stuck.

I have used junk 1/8" carbide ball mills for drilling out broken drill bits and taps. It ususaly takes a few. Unless the dowel pin spins I suspect you could put a hole in it. Then you'd have a pin with a hole in it, but I don't know if an extractor would bit into it.

Reply to
Polymer Man

Thanks for all your advice. After some fiddling I managed to get the pin pretty far back into the hole. Apparently it hadn't been fully inserted originally. I inserted a 3/16" roll pin, which is about 15 thou oversized. I used a pin punch to hammer it in and fill the hole. I tried unloading the spring tension on the pin and it held, so we went ahead and slipped off the retaining clip. With someone holding tension on the quill handle to prevent uncoiling of the spring, we put on the cover and reengaged the quill (it is disengaged to allow the handle to move freely). Everything seemed to work great. The quill moves down easily and if you let go of the handle it slowly moves back up. Now we can start making some chips! Thanks again woodworker88

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Reply to
woodworker88

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