robo_hippy
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There is always some bounce, if from nothing else, going through end grain to side grain, to end grain to side grain, the tools cut differently through each. You say you have a spindle adapter. This will put the bowl out farther from the headstock, so you have a longer lever arm, and it will not be as stable as a shorter one. If it is not running fairly true when you reverse it, that can be a number of things. Like Mike said, the chuck jaw screws can come loose, and that results in a little run out. One shaving between the jaws and the tenon can make it wobble. Some times you are not seating it dead on to begin with, and this is more of a problem when you are turning larger pieces. You can put the bowl on a table, put the chuck on the tenon, tighten it up and then screw it onto the lathe. Some times, just rotating it 45 or 90 degrees can make a difference, even though theoretically it shouldn't make any difference. When you reverse it, if it is 1/16 inch out of perfectly centered, that means + or - 1/32 of an inch, and that is very close. If you have more run out than that, it might be not getting it in the jaws correctly. If it is running fairly true, and you start cutting out the inside, and you get vibrations, this, again could be the spindle adapter. Shorter is better. Tool pressure can also contribute to it as in taking heavy cuts. If you haven't ground back the heel on your gouges, this can contribute. If you are really rubbing the bevel hard, that can do it. Hold the tool (sword in the movie I saw this in) as you would a bird. Too tight and you kill it. Too loose and it flies away. The bevel should rub the wood, but the wood should not know it.
So, it could be a lot of things. I would try to get rid of the spindle adapter first. I do have a video clip up about mounting things on the lathe. In the video section here, or on You Tube if you type in robo hippy.
robo hippy
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