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Thread: Wobble

  1. #16
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    6,565

    turning out-of-balance blanks

    Quote Originally Posted by Randy Hogan View Post
    ...It appears that the ballast weight of the machine is not substantial enough for the size of work I'm turning. ..
    A friend of mine turned lots of out-of-balance big blanks outboard on a small Delta lathe with no ballast. His solution was to fasten the lathe to the wall of the garage with long pipe clamps. The mass of the building was the ballast. Maybe try something more easily reversible like that first?

    The cast iron lathe bed can easily twist and is often overlooked. As a quick check put centers in the head and tailstocks, slide them close, and adjust one leg leveler until the points align. This will probably remove most of any misalignment. Since the floor may not be perfectly level I do this every time I move a lathe, even a few inches.

    JKJ

  2. #17
    Join Date
    Apr 2012
    Location
    Great Falls, VA
    Posts
    781
    Quote Originally Posted by Randy Hogan View Post
    I swept the shavings for the first time in awhile from around the base of the lathe. I noticed the whole thing had 'walked' several inches to the left. I've had, what appeared to be 'whole machine vibration' at the headstock end when I'm taking a big bite with a gouge at a fairly fast feed rate. I've checked and leveled the legs a couple times. It appears that the ballast weight of the machine is not substantial enough for the size of work I'm turning. I'm sure all of this isn't helping my wobble problem, although I have done some work recently without much run out at all. I think my next step is to put in some anchors in my concrete floor and anchor strap the head stock end down as tight as I can get it and see if this eliminates the vibration. When I first installed the lathe I had no vibration whatsoever so something obviously has changed. In addition, with a 22" swing, it doesn't appear the overall mass of the G0766 is heavy enough to handle it. The largest bowl I've turned is 16". But then again I'm new and I might be all wet.
    Randy, sorry you're having so much trouble. FWIW, one of my lathes is a G0766 that I've had for three years. No trouble at all turning bowls from heavy green blanks that begin at quite close to the full 22" swing. That's without adding ballast, and without anchoring the legs to the concrete floor. I have the legs sitting on 4" discs cut from an anti-fatigue mat of the type sold by Woodcraft, and that has eliminated any "walking", even when the workpiece is somewhat out of balance. You might want to try that before you resort to fixed anchors (which can cause other problems). Clearly something is going wrong for there to be so much vibration, but I'm quite sure it's not because your lathe doesn't have enough mass to turn to its full swing.

    But if you want more mass, you can easily add another 350 lbs simply by building a ballast box and loading it with seven 50 lb. bags of masonry sand. I did that with my other lathe, which is a G0733 (18" swing) that I've had for six years. When I first got it, I added 450 lbs. of sand in a ballast box (it's a longer lathe, so more space for ballast), thinking it would be necessary. It helps dampen vibration, to be sure, but I've found that if the blanks are prepared well, and rpms kept low until they are balanced, it really isn't necessary. I would not bother doing it again, which is why I've not done it with the G0766.
    Last edited by David C. Roseman; 09-14-2018 at 11:49 PM.

  3. #18
    All good points gentlemen! Your responses have given me at least 3 options to check out prior to me strapping the machine to the floor.

  4. #19
    Join Date
    Jun 2011
    Location
    Colby, Washington. Just across the Puget Sound from Seattle, near Blake Island.
    Posts
    787
    For many months I had a slight wobble on my Jet 14-42 and thought, "Damn! I somehow bent my quill." So when I had a chance to, I switched the main shaft for a slightly used one. Same problem. It still wobbled.

    Know what it turned out to be? I have one of those rubbery washers that fit between the chuck and headstock (to prevent over tightening) and it was crimped.

    So check for that sort of thing or, even, glue/debris where the chuck seats.

  5. #20
    Join Date
    Apr 2018
    Location
    Cambridge Vermont
    Posts
    207
    How large, heavy, and out of balance are the blanks you are trying to turn? What speed do you start off at? How wet is the wood? The larger the wood is the slower I start at. Often less than 100 rpm for really large stuff. It's not unusual for large wet wood to be out of balance even after I have turned it smooth. I assume it's that has to do with where the water is in the wood. I haven't turned green wood that has come from a tree that was felled only a few days earlier so I think that the moisture in the wood leaves unevenly. The part of the log touching the ground is cooler and the end grain can actually suck moisture in from the ground where as the part the sun will hit will be warmer and more likely to be drier. Of course that's a guess. Often when doing a bowl from wet wood it's not until I remove the inside of the bowl does the vibration go away to the point where I can speed up past 300 rpm. I haven't added ballast simply because I didn't want to make it harder to sweep up the wood savings under the lathe. I don't like the idea of attaching the lathe to the floor (my basement has radiant heating in it) or the wall because I do move it some as I fine tune where I want to to be. If I had a walking problem I think I would try the rubber mat under the legs trick.

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