Rex Edgar Posted March 2, 2017 Report Share Posted March 2, 2017 I'm working on a cherry bowl from a recently downed tree on the property. The blank came from a crotch piece. My question is that now that I've got it rounded, it still turns with a vibration and will not stay in any place on the spindle, acting as though it is imbalanced. Am I correct in assuming that the construction of the tree, where two branches begin, is not symmetrical in mass? That is no matter how round, it will always be heavier in some places than others? Quote Link to comment Share on other sites More sharing options...
Tpt life Posted March 2, 2017 Report Share Posted March 2, 2017 It will vibrate if your centers are out of alignment by a hair. Quote Link to comment Share on other sites More sharing options...
Marmotjr Posted March 3, 2017 Report Share Posted March 3, 2017 Yes Rex, the CoM (center of Mass) may not be in alignment with the turning axis, thus creating your vibration. Assuming your machine is setup correctly, as C mentioned, there is no way to avoid it. You can't melt the blank down and recast it :). Once it dries though, you might luck out and have it be less out of balance. Some tips for this if you wish to complete the bowl, and it's looking like it will be a beaut if you do. Make sure your lathe won't dance, secure it to the floor somehow if needed. Sandbags or bolting it if necessary. It might not be that extreme, just a vibration, not a dance. Faceshield faceshield faceshield! And if you have access to one, a baseball catcher's chest pad. And get anything fragile/important out of the line of fire. Sacrifice a bit of appearance here for safety. Use the beefiest mount you can in the chuck. If that means a flatter based bowl, so be it. You can make yourself a donut chuck to finish up the bottom. If you still aren't happy trying to turn it, you can always cut the piece up into smaller blanks for other turnings. There's still plenty of usable wood in there. 2 Quote Link to comment Share on other sites More sharing options...
Rex Edgar Posted March 3, 2017 Author Report Share Posted March 3, 2017 I'm satisfied with the lathe, it' a NOVA from New Zealand. I was watching a turning video from Down-Under and the turner was turning at 3200 RPM. I have never gone above about 1300 RPM. I set the speed at 1900-2100 RPM and turned the power on. (I had gotten the blank into a round shape and was beginning to remove the interior.) Well thankful we have gravity. The lathe began a dance and the blank escaped before I could power down, (this was with the base chucked and the interior held in place with the tailstock). Well the piece bounced a few times and the damage was minimal. I returned to my comfort zone, 600-900 RPM. I'll post progress as I go. The large crack worries me, but I'll see what comes 'as the bowl turns'. 1 Quote Link to comment Share on other sites More sharing options...
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