chuck wobble

[Jake Truxal]

After all the debating back and forth, I finally decided on the Vicmarc knockoff chuck from Grizzley. The first thing I made was a 6" walnut bowl, which I remounted a couple times after knocking it off kilter with a catch, each time it seemed to remount with perfect alignment. Then as luck would have it broke the bowl with a catch just as I was finishing out hollowing out the inside... :mad:

Next I made a 10" cherry bowl, which as soon as I mounted in the chuck was wobbling, I brought up the tailstock and slowed speed while I hollowed out but even once hollowed I was seeing a slight wobble. I removed the bowl and observed just the chuck. I seem to be seeing just the slightest wobble in the empty chuck. In addition to the Grizzley chuck, I'm using a 3/4" 10 tpi to 1" 8 tpi adapter from Penn State. Any suggestions on how I can determine if the wobble is being caused by my spindle, the adapter or the chuck?

 

[odie]

After all the debating back and forth, I finally decided on the Vicmarc knockoff chuck from Grizzley. The first thing I made was a 6" walnut bowl, which I remounted a couple times after knocking it off kilter with a catch, each time it seemed to remount with perfect alignment. Then as luck would have it broke the bowl with a catch just as I was finishing out hollowing out the inside... :mad:

Next I made a 10" cherry bowl, which as soon as I mounted in the chuck was wobbling, I brought up the tailstock and slowed speed while I hollowed out but even once hollowed I was seeing a slight wobble. I removed the bowl and observed just the chuck. I seem to be seeing just the slightest wobble in the empty chuck. In addition to the Grizzley chuck, I'm using a 3/4" 10 tpi to 1" 8 tpi adapter from Penn State. Any suggestions on how I can determine if the wobble is being caused by my spindle, the adapter or the chuck?

Jake......

Start from the source, and work up.....

If there is no wobble in the spindle, put the bare adaptor on and try to determine if it's true. If both are ok, then it's the chuck.

Some woods warp as you turn......could this be entering your equation?

good luck

ooc

 

[Jake Truxal]

Great minds think alike I just came back from trying exactly that when I see your reply. I MAY repeat MAY have fixed or minimzed the problem. I could definitely see wobble in the chuck. took all apart and cleaned threads on everything and still saw wobble, so worked backwards. Took off the chuck, left the adapter and insert and still saw wobble. Removed the insert and still had wobble on the adapter. So I figured either the threads on the spindle or adapter aren't true or maybe the mating face on one is not true - since it's only 8 tpi there is alot of play until the adapter tightens against the spindle, so I figure if one surface is not perfectly square it will cause wobble when they meet. I tried putting a 1/8" thick nylon washer between the spindle and the adapter and that seems to have eliminated at least any wobble that I can visusally see on the adapter. I mounted the finished bowl back in the chuck and still have some slight wobble but that could be due to mounting differently. I marked the original mount point but rotated it several times while turning trying to eliminate the wobble but didnt mark the final mount point. So I won't know for sure until I turn the next bowl.

This brings up a related stupid question - what are the indexing holes on the back of the chuck for? How are they used?

thanks.

 

[odie]

Great minds think alike I just came back from trying exactly that when I see your reply. I MAY repeat MAY have fixed or minimzed the problem. I could definitely see wobble in the chuck. took all apart and cleaned threads on everything and still saw wobble, so worked backwards. Took off the chuck, left the adapter and insert and still saw wobble. Removed the insert and still had wobble on the adapter. So I figured either the threads on the spindle or adapter aren't true or maybe the mating face on one is not true - since it's only 8 tpi there is alot of play until the adapter tightens against the spindle, so I figure if one surface is not perfectly square it will cause wobble when they meet. I tried putting a 1/8" thick nylon washer between the spindle and the adapter and that seems to have eliminated at least any wobble that I can visusally see on the adapter. I mounted the finished bowl back in the chuck and still have some slight wobble but that could be due to mounting differently. I marked the original mount point but rotated it several times while turning trying to eliminate the wobble but didnt mark the final mount point. So I won't know for sure until I turn the next bowl.

This brings up a related stupid question - what are the indexing holes on the back of the chuck for? How are they used?

thanks.

Grizzly is pretty good about replacement, so if you can't live with what you got......replacement is always an option. It would be difficult to find a chuck that isn't out of alignment by a couple thousandths, but if you can visually see the wobble, I'd have a hard time living with that permanently.

Some chucks have indexing holes. The indexing holes are to provide reference points for equal spacing around the circumference of your work. I know that some lathe turners use these for decoration purposes on their workpiece. I have the indexing included on my Woodfast lathe. I believe it's divided into 32 spaces, but, I'd have to check to be sure. I seldom have had need for the indexing.

ooc

 

[john lucas]

Don't worry about the threads. It's the mating surfaces that pull everything into alignment. If you have any grit on these surfaces it can throw them off. Since you have essentially 2 surfaces instead of 1 you could easily generate some wobble with grit.
Make sure you are checking the chuck itself and not the jaws. The grizzly jaws aren't as exact as the vicmarc. They seem to be OK when tightened against something but are really loose otherwise. My Vicmarc chuck inner jaws are much better machined and align better.
You will almost always get some wobble out of the wood. It's very difficult to get wood to align properly when inserting into a chuck. The fibers don't crush the same in all directions and can easily throw things off. Heck even machinists will tell you not trust a 3 jaw self centering chuck and they are machined a lot tighter than our wood chucks.

 

[Joe Greiner]

Index holes

When you need indexing (and you probably will, eventually), the index holes on the chuck could be superior to a separate index disk or an internal pulley, because they're on the chuck itself and don't involve your lathe's drive train - a more direct connection to the workpiece. I've attached a picture cloned from another forum, of a simple latching mechanism for lathes with motors intruding into the work space (one benefit of such a design "defect").

If your lathe doesn't have that "defect," you'll need to devise some other bracket to reach the chuck.

Grizzly's 24 holes, and Vicmark's 32, seem to limit your options. But an extra hole in the latching bar or bracket can multiply those numbers.

 

[Steve Worcester]

read this thread for determining what is wobble and runout and how to measure it.

http://www.aawforum.org/vbforum/showthread.php?t=6620

 

[MichaelMouse]

Now a micrometer is certainly a wonderful thing, but is knowing how far "out" really as important as all that?

Use a straightforward touch gauge. The end of your short toolrest might just do. Get it up as close as you can to the piece being verified, and see if the gap varies as you rotate by hand. If you're one who just has to know, a set of feeler gauges is a lot cheaper than a dial or digital indicator with magnetic base. Also likely to be a bit more useful, because it'll bridge the threads when you use it to check the spindle.

I've only had trouble with my chucks twice, and both resolved themselves to improperly mating surfaces. In the one case it was some cutting flash, in the other, a chunk of shaving. I cleaned, snugged, and tightened.

I test spin my mounted pieces by hand before I start working them to save surprises. If they're rough, I watch the front versus my live center, if they've been turned outside and reversed to hollow, I check the outside. A tap and snug sometimes required if I failed to seat things properly.

 

[Joe Greiner]

While we're on the subject of mating surfaces, sometimes the fit can be too perfect, i.e. chuck body to spindle boss, and removal can be difficult after a catch. Nip this problem in the bud, by adding a thin plastic washer (cut from the flat side of a juice or milk bottle) at the interface. Also, secure the chuck to the spindle with tools, instead of spinning it home. BTDT

 

[Steve Worcester]

Now a micrometer is certainly a wonderful thing, but is knowing how far "out" really as important as all that?....

If you ever want to remount a piece once removed from the chuck or reverse it end to end, it is paramount that everything is as true as the machine will allow.

The micrometer gives you an idea of how far in numerical terms, if you are trying to get to a couple thousands, the wood moves that much. But knowing how far out is where you know how much difference you make after adjustments.

I like quantifiable, measurable results.

 

[MichaelMouse]

Guess when they make a calibrated micrometer correction adjustment, I'll use one to check how far to crank it. Until then, it's either in or out. If out, it gets a loosen and tap until it's in.