Finding balance Off center bowl turning

[Brian Brown]

About 8 weeks ago, I trashed my knee. It didn't heal, so yesterday I had surgery. Now the wife thinks I can't turn for 6-8 weeks. So now I just sit watching Youtube vids. Just before I wrecked the knee, I was working on a new project with off center turning. I have attached a few images here of some bowls that have a similar technique. Getting them off center is no problem, but the vibration from being off center is terrible. I have searched the web for information on balancing the load, but no real solutions. Most of the guys I have seen doing this stuff rely on very heavy lathes and small diameter bowls. I am using a midi (Delta 460) and the lathe is all over the place. I am literally chasing the lathe around the shop. I know I can use sand for ballast on my stand, but I think the vibration will break all the joints on the stand, and tear it apart. I am trying to turn 12 inch pieces, and the vibration causes very poor quality cuts, especially since some are so far off center that I am turning some air. It is downright dangerous even at slows speeds. I thought I remembered some threads here years ago, when I was first starting to turn, that talked about using tire weights or fishing sinkers for weight to balance the load. I did a search, and it seemed to turn up almost every thread here. I did find this thread, which was some help, but it got me wondering if countering the off balance issue with weights would be better for the bearings on my lathe than adding ballast?

http://www.sawmillcreek.org/showthread.php?203374-Out-of-balance-Lathe-weight-or-a-simple-fly-wheel&highlight=tire+weights+balance

Does anybody have any thoughts on how to balance the off center stuff, and how to attach weights securely and safely? What would be the best way to determine if the load is balanced before firing up the lathe? Any other thoughts or recommendations? I would like to not do damage to my lathe and keep all my body parts as they were when I do this. I have had enough of Doctors and hospitals with the knee.

[Geoff Whaling]

Brian,

I do smaller off center work on a large lathe so its not a significant issue to me, but it is surprising how significant dynamic balance becomes even with small offsets or wood with voids etc.

You could look at something like the Vicmarc balancing system - http://www.vicmarc.com/default.asp?contentID=550

Plenty of turners use all sorts of weights screwed to a larger face plate, but as you say there is the hazard of them parting company with the face plate. The significant issue is that the balance is dynamic and constantly changing as you remove wood. As for testing initial balance I would suggest slackening off the drive belt so the lathe spindle can free spool and find its natural resting position with the face plate & blank attached. Then its a matter of checking as you turn.

[Thom Sturgill]

I don't remember who did the turning, but i do remember seeing pictures of a rig someone made where the piece is held in s fixture which has the weight balanced. Something like mounting it to a glue block screwed to a backing plate that has weights distributed around it. These weights would need to be moved to adjust for changes as you remove material. Another idea would be to 'waste' some wood by turning the bowl centered and then removing part of one wing. Turning at speed is pretty much required to prevent the gouge from slipping in and catching on the next blade of the wing.

[Grant Wilkinson]

I've done a couple similar to the one in your first pic. I hot glued the blank to a piece of plywood that was on my faceplate, then hot glued weights to the plywood. As wood comes off the blank, you need to move the weights.

[Reed Gray]

The most difficult part of turning off center pieces for me is slowing the lathe down. Just like when you mount a bowl blank that is not balanced, you turn the speed up till it starts to shake, then back off a bit. Patience.... I doubt I would turn some thing like you picture at anything over about 500 rpm, where if it was a standard bowl, I would be in the 2000 rpm range.

robo hippy

[Bob Hovde]

Does anybody have any thoughts on how to balance the off center stuff, and how to attach weights securely and safely? What would be the best way to determine if the load is balanced before firing up the lathe? Any other thoughts or recommendations? I would like to not do damage to my lathe and keep all my body parts as they were when I do this. I have had enough of Doctors and hospitals with the knee.

Brian,

Have you considered attaching (glue, tape) a longer board to the back of the one you are turning. After turning the flat top and the bowl inside, reverse the long board and do the back.

[Brian Brown]

Bob,

I had not really thought of a longer board, but did think about using a round piece of wood behind, and reversing as you suggested, but the problem is that I probably would use a curved or contoured rim rather than a flat rim. Maybe I could try to make an inverted version of the contour in the backing board, and mount it that way. Then there is also the off center balance issue. Holy cow, this is getting complicated! Why can't I ever try something normal? On the bright side, I just got back from the ortho Doc, and he pronounced me the poster child for proper healing, and released me from all restrictions except kneeling. I don't need to kneel to turn…. Weekend coming…. Wife thought I wouldn't be able to do yard projects….. Hmmmmm.

[Bruce Pratt]

For at least Pictures #1 and #2 glue an extra block of waste wood on with a paper joint so you have a symmetrical piece. Turn as normal, and remove the waste block when finished.