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How I was able to center my 5-C collet chuck

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  • How I was able to center my 5-C collet chuck

    Hi Guys,

    Since joining this forum in SEP of 2007, I have learned much from you guys. You’ve been tolerant of my inexperience and forthcoming with *most helpful information* all of which is gratefully appreciated (far more than you will ever know). It’s rare that I am able to make a positive contribution unless, of course, others should by chance garner useful information from the plethora of questions I frequently ask. On a chance that a few other member of this forum are as inexperienced as I, I would like to think that I am about to make, what may very well be, my first positive contribution. For the “old salts”, simply ignore this post for what I have done I’ve learned from you.

    In 1980, I purchased my first lathe and milling machine (both used). For little over a decade I spent hours and hours of pleasurable time with my machines. In 1992 tragedy visited my home. My youngest son was killed and I sold all my equipment. In 2007 I made a choice to “start again” and I bought a *new* lathe. When ordering my new lathe I additionally ordered a 5-C collet chuck. It was Chinese made. From reading on the forum I learned that collets & chuck were basically designed for repeatable accuracy and their ability to hold small round stock. My order came with a backing plate (which had to be fitted to the chuck) and the chuck. Care was taken when fabricating the boss on the backing plate. When finished it was a snug fit. Holes were located, drilled and tapped, and the chuck was secured to the backing plate. Regardless of careful measurements and turning, the chuck was consistently out-of-round by .006”. What was I to do? I set aside the collet chuck and resigned to using the 4-jaw. Then, last year, I mounted my Super Spacer on the milling table. Thought I had purchased the one that was adjustable. Not so and the chuck was running ~.002” out-of-round. Referring my dilemma to the forum, one of the members helped me solve my problem. He stated that if I slightly loosened the securing bolts on the chuck, there was a good chance that sufficient “play” was left that I could lightly tap the chuck until my work piece indicated zero. That worked and I tightened the securing bolts re-indicated, and all was well. I viewed him as a genius ….. and I still do. This brings us up to this weekend.

    I had a need to use my collet chuck but I knew that the chuck, and not my installation, was a problem. Under close inspection I realized that the counter sunk holes (bolt holes for securing the chuck to the backing plate) in the chuck body did not have a flat shoulder on which the cap-screws could squarely engage. The counter sunk holes were only drilled, not milled, leaving a beveled shoulder on which the cap-screws would scoot around. I also learned that the through-holes were tight and the furnished cap-screws were touching the walls in each hole.

    To solve my problem I removed my chuck from the backing plate and took a facing-tickling-cut off the surface of the backing plate where the back of the chuck engages the backing plate. The boss on the backing plate (which fits inside the recessed area of the chuck) was previously turned to be a “press fit”. I turned the OD of the boss by .012” to provide a small amount of play. Next I enlarged the three “through holes” in the chuck’s body so that the cap-screws did not touch the walls. I then milled the bottoms of the counter sunk areas *flat*. I slightly turned the OD of the cap-screws to ensure they didn’t touch the counter sunk walls. After cleaning all mating surfaces of “machining chips”, assembly took place. Using a 1” piece of ground & polished 4140, I indicated near the face of the chuck. It was approximately .013” out-of-round. I slightly loosened the bolts, just like I was told to do on the Super Spacer, and gently tapped the chuck and re-indicated. I was making progress. I repeated the previous step until my indicator read ZERO. I torque the cap-screws securely, re-indicated, and all was well.

    So my 5-C collet chuck is dialed in, I’m happy, and I owe gratitude to this forum and a member (genius) of this forum for giving me this idea. If other “up-starts” are experiencing this problem, you may want to consider trying what I did or maybe alter this method …. but it has worked for me. In passing, there may be a possibility that similar alterations could be made to the non-adjustable 3-jawed chuck. I would assume that because of inaccuracies in the scroll, it might be necessary to re-adjust setting when changing to larger or smaller stock.

    Harold
    For those having fought for it, Freedom has a flavor the protected will never know.
    Freedom is only one generation away from extinction.

  • #2
    so what do you get, when you indicate 5 and 10 inches from the collet chuck?

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    • #3
      Originally posted by dian
      so what do you get, when you indicate 5 and 10 inches from the collet chuck?
      Hallo Dian,

      I haven't even tried that because it's doubtful that I will ever work on a piece that long when using the 5-C chuck. I purchased the chuck for the express purpose of fabricating small, short parts. I will likely use it as well to hold small screws, etc.

      Harold
      For those having fought for it, Freedom has a flavor the protected will never know.
      Freedom is only one generation away from extinction.

      Comment


      • #4
        I bought one of those 5-C collet chucks also. I used a home-made transfer punch to mark the bolt hole locations, and carefully drilled, then tapped the holes. My chuck fit with an easy slip-fit to the backing plate. The backing plate, when bolted to the spindle of my lathe, read .0002" out. I took a very light skim clean-up cut on the face of it, and the centering boss.

        When the chuck was bolted up, and a ground test bar was clamped in the collet, I came up with .00005" TIR, four inches from the spindle....Close enough for guvmint work. Since installing it, I've had it off and back on several times and the run-out stays very consistent, so, I'm happy.

        It works so well, I hate to remove it when the need arises.

        Who says you can't do decent work with one of those Chinkanese lathes?
        No good deed goes unpunished.

        Comment


        • #5
          Nice job, Harold, both in analysis, repair and write up.

          Although I'm no expert, I would have taken my runout readings from the inside taper of the chuck. That way I'm not adding collet error (from one of many collets with varying error) to the 'zero' centering of my chuck, something you can easily do now if you should want to try.

          Have fun!

          Fred

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