Wanted: An accurate chuck

[Roger Chandler]

If there is slop in the scroll gear or the jaw slides it might have an effect on how true the jaws mount. Another possibility is that a jaw slide might be out [machined incorrectly] which could affect the runout of the jaws as well......

After all this, if I were Jim, I would call Teknatool directly and speak with the tech people, and just tell them all that he has gone through and ask them to replace the whole chuck apparatus and jaws........ask them to check the thing out before shipping, and send them your defective chuck with the original insert that you purchased.

I'm just sayin' ....

[Van Huskey]

I hope you're not equating 1/10 (.1") with ten thousandths (.010")...

No, I was saying in your current state of depleted karma and luck the best you can expect .1", any better than that and you should be popping champagne and dancing around the shop to this:




It was just a continuation of the joke.

[Dom Garafalo]

Now I'm supposed to receive the new dovetail jaws tomorrow, so we'll see if they exhibit the same problem....

Any new discoveries? Just hoping you solved your problem.

[Brice Rogers]

When I read John Jordan's comments, it made me think of what could cause this and what could fix this. BTW, I'm cast and machined 2 or 3 sets of jaws so I am fairly familiar with the process, construction and things affecting tolerance. My jaws didn't do this.

The problem could be either the jaws or the chuck itself. The distance from the imaginary center to each ends of the arc are different. That means that either the bolt holes in the chuck don't point to perfect center or the bolt holes in the jaws don't point to the perfect center. The alignment ring on the back is typically not a terribly tight fit, so it could allow the jaws to each be rotated on their axis.

If a person were trying to correct the alignment, they could take a needle nose file (or a mill) and elongate either the outer ring of holes or the inner ring. That would allow things to align correctly. But that probably would not stay put under turning forces. That is what made me realize what the problem is.

Perhaps the OP could check the chuck to see if four holes are perfectly aligned, and also with the jaws in a circle if the same is true. But the tolerances that are driving him crazy are pretty small and it might be hard to visually see.

[Bert Delisle]

In my opinion one can not go wrong with Vicmarc or Oneway. I have both stronghold and talons and Vicmarc 120 love them. Occasionally have to change adaptors for demos on club lathes. Oneway Talon is my " go to" chuck for this case. The taper adaptor has fantastic repeatability when installed correctly. Vicmarc and Stronghold are my bowl chucks and have handled every thing I have tried, including coring a 23" x 12" bowl blank for nested bowls.
I have a couple or three vicmarc knock offs and a nova G3, they are far and away inferior compared to Vicmarc or Oneway. My Knock-off chucks work ok but rattle when spinning , only use them for light work, and the G3 scroll is opposite all my other chucks so get to collect a lot of dust between uses. well that is just my two cents worth.
Turn safe and have fun.
Bert

[Jeffrey J Smith]

I've got both Vic's and Oneways. Both are good chucks. I prefer the oneways - simple to clean, and all 7 of them are totally interchangeable. A set of versa-slides allows Vicmark jaws on the oneways when needed.
A while back a guy who used to demo for oneways mentioned that every now and again, it's a good idea to make certain the adapter is seated well. Give it a few taps then re tighten the screws. Amazingly, you'all get a few turns every time- at least I have.

[John K Jordan]

...That means that either the bolt holes in the chuck don't point to perfect center or the bolt holes in the jaws don't point to the perfect center. The alignment ring on the back is typically not a terribly tight fit, so it could allow the jaws to each be rotated on their axis.

The idea to check the bolt holes is a good one. In this case, I can't imagine it being an issue for one reason - every Nova chuck and jaw set I have here has fairly tight tolerances on the alignment rings. In fact, they are so tight I found the instructions in the manual were needed a few times, specifically to tap the jaws into the chuck slides with a block of wood, at least at first. Usually they fit well in the slot but even without tightening the screws the only play I've felt has been a tiny bit in the jaw slides in the chuck body.

The manual also instructs to install the screws until snug, back off 1/2 turn, then close the jaws and make sure they are a tight circle before tightening the screws. I assume this is to take care of any tolerance in the countersunk screw holes that might allow the jaws to be shifted a little to one side or the other. This has worked well for me for all my Nova jaws and chucks.

I can imagine that ignoring these instructions would result in sloppy jaw closure, but I can't imagine how it could result in the type of misalignment Jim illustrated. Very curious. I would still love to examine that chuck and jaws, compare them to some here, and perhaps measure things on the surface plate and maybe in a rotary table with a dial test indicator. Sometimes a second set of eyes can spot something. Or maybe Jim has it sorted out by now.

JKJ

[Leo Van Der Loo]

Don’t forget we never saw an actual picture of the jaws in the chuck.

And I know enough of machining to say that jaws can’t be machined as a set, the way it is shown in the picture, and the tolerances, even not being very tight in wood chucks, they could not be rotated that much to have them sit that way.


Jaws presumed this way.jpg

[Michael Mills]

The step which John K mentioned in scrolling the jaws shut with the screws about 1/2 turn loose should correct alignment if they are off.
I have several Nova; on one G3 I had run out. Removing the insert and going around the interior of the chuck with an oiled q-tip picked up a very small shard of metal from the milling. Run out problem was solved.
I purchased a used SN on the bay for <$10 because it had run out problems. Three of the four jaws were installed in the wrong position. Reinstalling properly the chuck ran true.
I do not remember which was for the circumference and which for the face but I believe Nova states they should be less than .004 and .005.
My only problem with run out over .004 was when I tried to use a WC knockoff insert, IIRC it was .014 which was easy to see.

[John Sanford]

Then I installed all three sets of jaws in my possession that fit this chuck and inspected them. I have the original dovetail jaws it came with the chuck when new, a set of step jaws, and a set of pin jaws.
However, EVERY SINGLE ONE of the jaws I own for this chuck, have the same twisted aspect illustrated in the drawing I shared earlier. This indicates that the manufacturer hasn't machined these jaws correctly. In each case ONLY the leading edge of each jaw contacts the work piece. And, the part of the jaw that does NOT touch misses touching by a significant amount. I did not measure, but I daresay it's at least .030" off.

Actually, it sounds like the manufacturer didn't machine the CHUCK correctly, specifically, the mounting points for the jaws. That all three exhibit the same problem points at a common root, and what do all three have in common? The chuck.

I hope you can get this sorted out. Of course, if the Talon exhibits the same problem with it's new jaws, then, once again, have to go back to the common root. Which would be either the lathe, or the operator. Sorry.

I hope you can get it sorted out.

[Jim Underwood]

Sorry for the long absence. Been a little crazy what with a scheduled outpatient procedure that took more prep than I wanted... If I say more it will be TMI. Thank God that's OVER!

The Oneway Talon smooth jaws arived (#2 I think), and once put on, ran as true as one could expect. And they did VERY well for me turning a plate that had to be reverse turned. I like them much better than the OEM serrated jaws. Once I finished that, I put the serrated jaws on and inspected them once again. They are NOT twisted as I described in the pictures above. So I was wrong about that.
Apparently if one is to true these up one needs to open them to the original diameter that they were machined at. Once I did that, both sets of jaws were reasonably true. Where'd I'd made a mistake before was in assuming that they should be trued up with the jaws totally closed. NOT TRUE. Once should put a proper thickness spacer between the jaws to bring them out to the proper diameter, and then close the jaws on that, and THEN true them up. So my confidence in the Oneway chuck is restored. I think what happened is that I had too many new items have problems at once and just lost sight of basic troubleshooting procedure- follow the tree, don't skip around..... and deal with ONE problem at a time.

As for the NOVA G3, upon closer inspection, the original smooth dovetail jaws were twisted as described above, as were the pin jaws. The step jaws were not twisted. So I have two sets of jaws that seem to be twisted. I'll have to re-read this thread to remember the troubleshooting tips several of you have been kind enough to point out. The seating of the jaws in the grooves is a good tip. I'll check that as well...

Anyway, thanks to ALL of you for putting up with my rant and giving me some significant help and moral support... and the hilarious comment about my Lathe Karma being used up.

I'll let you know what happens with the G3. It might be up for sale and being replaced by another Talon...

PS.
OH YEAH, I'll try to get some pictures of the problem jaws and put 'em up here...

[robert baccus]

Let's see. I commonly turn 12 to 20" vases and urns. I use a single screw(with very strong wood) in a glueblock glued to green wood using 2" jaws on several Nova 2 chucks. I also use dovetail ring faceplates on 2" dovetail jaws and the same vases. The blanks run from 50#'s to 120#'s--green of course. Turned, waxed and then returned with a oneway stabilizer. Local woods as well as purchased woods are used and any runout is simply not tolerated. Now what can a chuck do more than this. I think all the namebrand chucks can do the same if the lathe and jaws are up to it. Add in some critical thinking and some confidence in you own abilites.

[Steve Doerr]

Jim,
I've been thinking about your questions and today I did a quick check on my chucks. I have two Super Nova 2's and two Nova Titans. The Titans run true and thus when I turn my turnings around they are spot on. I had one Super Nova 2 that I couldn't get any of my turnings to run true once I turned them around. Sure enough, the chuck itself was not running true. Thus, no matter how hard I try I will never be able to have my turnings run true. The question is, is it the chuck or the threaded insert that is not running true? The other Super Nova 2 is spot on. The lesson I have learned here is when I buy a new chuck, the first thing I will do is check to make sure it is running true. If not, back to the dealer it goes.

[John K Jordan]

The question is, is it the chuck or the threaded insert that is not running true? The other Super Nova 2 is spot on....

Could you swap inserts between the two SN2s and see if the problem moves with the insert?

JKJ

[Jim Silva]

5 pages long so may have missed someone else mentioning this but I've run into an issue like this that was caused when going from my DVR XP to a 3520b. The spindle of the PM is a hair longer than on the nova. This caused the chuck to wobble as it didn't bottom out against the machined shoulder of the spindle as it should have. Solution was to take a 1/8" piece of melanine (sp.. read thin, stable fiberboard like pegboard without the holes...) with a hole drilled in the center just barely able to fit over the threads on the spindle. This rests against the spindle shoulder and lets the chuck insert land flat eliminating the wobble.
Worth a try.

Jim