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First somewhat major crash on the Bridgeport (and minor on the lathe)

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  • First somewhat major crash on the Bridgeport (and minor on the lathe)

    Well, it's not been a good couple of days in my shop.

    First, I had a friend stop by while I was working in the shop. I was finishing up turning down my 5C collet closer tube, almost done. Got near the chuck, cranked out the cross and turned 'er off. Talked a bit as I got some scotch brite to polish it, turned it on and started polishing. Anyone see the problem? Anyone??? I did not disengage the clutch!

    While working the pad, I glanced at the tool post and thought, "Dang, how did it get so close to the chuck?" Then it hit me just as I hear the first light taps. I grabbed the feed handle with one hand and hit the clutch with the other. Just in time, didn't even mark the jaws and just took a small swipe of paint off my AXA holder. Whew!

    Lesson learned (and should have known without having to experience it), no talking while running a machine. I’m too green to keep up with everything at once without focusing all my attention on it.

    Then today (alone) I was hogging away at a Kennametal 1" TPG holder to adapt it to my 1/2” tool holders. It was set horizontal in my vise, cutting on the back (turret) side, with table moving left to right (standard milling, not climb milling) with the cross gib locked (though not terribly tightly), using a 1/2" 3 flute solid carbide hogging cutter. All of a sudden, it got much louder and things started getting that "watch out" characteristic as I reached for the switch with my left hand as started dialing out the cross feed and simultaneously trying to identify the problem. Then I noticed it had pulled the table in almost exactly 0.100 (according to the DRO) toward the turret!!! Wow! Never imagined it could move that much! I took up the slack coming in toward the cut, and the cutter sucked in the slack, plus it must have gathered up all the flex in the entire machine (lifting the knee to I suppose?) to move that much! I’ve made cuts just as heavy on HRS and CRS before, but the combination of whatever alloy forms that insert holder with a cutter that seems to have been getting a bit dull, made it really grab hold! Scrapped the holder and the end mill, but I only had $5 in the holder and about $8 in the end mill (CNC pull off), so no big loss...

    This is the first I’ve ever really “crashed” the lathe OR mill. It could have been MUCH worse, and I guess I should be happy that no real damage is done, but it’s been humbling coming one right after the other like that at a point where I was only just beginning to feel like I had a glimmer of understanding developing. I’ve always been very cautious and painfully aware of my lack of training as I try a little more and a little more till it starts sounding like it’s complaining. But I guess you really never know where the limits are, or what the results will be, until you’ve exceeded them.

    I’ll be much more cautious in the future, it’s all part of learning...
    Master Floor Sweeper

  • #2
    Bad Dog-- Sorry to hear of your difficulties, and glad you weren't injured-- Thanks for sharing this info with us-- As a newby to the world of machining, these are the kinds of incidents I do NOT want to experience-- As I have told my sons who are firefighters, any time you can learn from someone elses' mistakes, you are getting a free lesson-- Somebody else paid the price-- I've already learned, that when bad things happen while milling, they happen QUICKLY-- So far it has only cost me a couple of broken end-mills-- Best regards--

    I know I just had it a minute ago--


    • #3
      Always lock the crossfeed or longitudinal that is not being used to feed the work into the cutter.

      Always disengage the carraige or crossfeed on lathe BEFORE stopping chuck.

      Get into that habit right now.
      It's only ink and paper


      • #4
        Thanks guys.

        And I thought I was into that habbit already, but all it took was a little distraction to screw me up.

        And saddle on the mill table was locked, though not torqued down as hard as it probably should have been. I had, however, not locked the knee, which no doubt did not help...
        Master Floor Sweeper


        • #5
          Them ain't crashes! Them's Almost. Almosts don't count. They're just part of learning.