Need Help - Wobble after chucking

[Dan Cannon]

Hi all,
I'm still getting used to my new lathe and have been playing with it as much as possible the last few days (although time comes at a premium right now). One thing I've noticed on a few of the practice spindles I've done is that if I start between centers, work the piece a little, then turn a tenon, flip it and chuck it up with no tailstock to finish the end, I inevitably get a little bit of a wobble in the piece. As far as I can tell, there is no wobble in the chuck itself, or the spindle, so I'm thinking I'm not chucking properly or I'm not turning the tenon properly. Keep in mind, this isn't just a new lathe to me, but my first, so I don't have anything to compare to. Just wondering if this is something that goes away with practice, or if I'm simply not approaching it the right way.

The pieces I've been working with are about 1.5" diameter spindles, maybe 4" to 6" long chucked in pin jaws with the tenon about .75" diameter. I've been turning the tenon, then putting the piece into the chuck so that the jaws are right up against the main part of the wood. Any ideas???

Thanks!
Dan

[David E Keller]

I don't think it's all that uncommon to need to true up a piece after placing it in the chuck. If it's not the chuck or the lathe, it's probably the turner or the wood.:)

If your tenons are cut properly and the shoulder cut is flat and square then you're good. I often use the tail stock to center the piece when putting it in the chuck before tightening the jaws... That helps me a little bit. Also, make sure that the jaws and piece are clean before chucking... Sometimes a little curl will get in between and cause some trouble.

The wood matters as well. Sometimes the chuck jaws crush the wood fibers differently on one part of a piece than they do on another. That can lead to a little eccentricity, too. I don't think you can avoid that really, but you can plan for it when turning.

I hope that helps.

[John Hart]

I think David hit it.

[Mark Hubl]

+1 on what David said. You said that you were inserting these about 3/4" into pin jaws. Sounds like you are creating a shoulder on your tenon? With the shoulder seated flat against the jaws it will help keep things square as you tighten down on the tenon. The more you squeeze the jaws into the wood the more wobble you may experience. You don't want it flying, but you don't want to crush it too much either. Also, how extended are your pin jaws? Is your tenon 1 1/2"? Most jaws tend to work more efficiently the closer they are to there fully closed position. There usually is more jaw contacting the wood this way.

If you are experimenting with spindles, bobbins, finials etc. and you want to finish the top, you may be better served to rough the spindle between centers, make your tenon, then go to the jaws right away. Use your tailstock and chuck to re-rough the spindle and then shape it. When done then remove the tailstock and finish off your end. You may want to slow the speed down a bit when cleaning up the end as well.

Now if you are playing with finials and very fine work, that brings up some other issues with using the tailstock. Most turning very fine finials will chuck and rough it with the tailstock in place and then remove the tailstock and work back to the headstock. Good luck.

[Thom Sturgill]

Inserting 3/4" into the jaws may be too much - the tenon only needs to be 3/16 - 1/4" in depth. The shoulder should be square or a little undercut so that the wood rests against the end of the jaw at the outermost edge. It should contact all the way around. The diameter should be just larger than the diameter of the jaws all the way closed.

Another thing - since you are cutting the tenon at the tailstock end, if the tailstock is not in perfect alignment there will be some wabble.

[Jake Helmboldt]

Dan, the problem might be the pin jaws and how tight your are cranking down on the chuck.

1. as mentioned you can crush the wood fibers, and long and short grain will compress differently, resulting in wobble.

2. pin jaws can flex, especially if overtightened, which will also result in the wood not being truly centered.

I would try another set of jaws (like #2 jaws) to see if you have the same problem. As mentioned, try to make the tenon close to the same diameter, and tighten just enough for the chuck to be snug. Even with a heavy bowl blank you don't need to go too tight (in fact you can increase the chance of launching the blank by crushing the tennon.)

[Tom Sherman]

Dan another thing you may want to look at is the alignment of your tail stock with your head stock. To check this you would want to put a drive center in your headstock and bring your tailstock up till it almost touches and compare where the points are in relation to each other. You may have to make a minor adjustment to the tailstock to line them up.

[Thomas Canfield]

Check the depth from the shoulder to bottom (ususally 1/2") and make sure tenon is shorter. The shoulder should make full contact. I have found on some of the softer woods that applying thin CA to tenon and shoulder help with bowls. I don't have experience with spindels, but a 1 1/2" D and 6" long on a 3/4" short tenon sounds a little light to me. Someone with experience needs to give you a suggested tenon size.

[Paul Douglass]

For a spindle wouldn't a steady rest come in to play here.

[Rich Aldrich]

I think the guys have covered it but one issue.

I am a green (new) turner, pardon the pun and had issues with runout. One of my biggest issues was how sharp the tools are. I found that the duller the tool, the more pressure exerted which results in out of round. The cuts arent as even around the wood. I found this especially true on bowls where the bowls change grain direction.

[Dan Cannon]

These are all great suggestions, and I'll be doing some more investigation with all of it tomorrow. Thanks everyone, I'm sure I'll get this straightened out sooner or later (pun intended)

Dan