Chuck isn't consistently square?

[Daniel Miller]

Hey all. I've been dealing with this issue for as long as I can remember and I'm really not certain if I have a problem or not. I'd like some input from you guys. This issue is most prevalent when I'm turning pepper mills and having to flip the blank around for forstner bit drilling purposes.

I have a Teknatool Supernova 2 chuck that I've had for seven years now. I've got a bunch of the various jaws for it. I've consistently noticed issues with what I perceive to be the chuck not keeping a blank square to the tailstock if I have to remove the blank for some reason. Now that being said, I do understand that a person should definitely limit the amount of times that they're removing and then rechucking a blank, but I feel like I'm getting a more dramatic out-of-round turning than a person should reasonably expect.

Take a look at this video from Craft Supplies USA:

View: https://www.youtube.com/watch?v=ikQCc5JD0wk
. Between the 2 and 3 minute marks, you'll see that he's squaring the blank over time and turning his tenon for the chuck. Around 3:00, he chucks the bottom of the blank and proceeds to create a tenon for the other half of the blank. You can see how smoothly and squared that the blank is turning, but if I did that with my chuck, there would be a clear fuzziness as it spun where you could see that it wasn't spinning true. I've noticed with my chuck it doesn't always seem that each of the sections of the jaws are contacting a blank, and it usually appears that there is always a miniscule gap in some places between the jaw and the wood where they should be touching.

All in all, I'm wondering if others experience the same issues with their chuck or what your thoughts would be on where I need to start troubleshooting to figure out if the problem is the chuck or something else. Thanks for any input!

 

[Doug Freeman]

I have a Nova G3 chuck, and others. I mostly use serrated vs dovetail. All my chucks have an “alignment mark” I etched in the body. When I mount a piece I mark the piece in that spot allowing replacing the tenon back into the same orientation. I always put a small shoulder for the top of the jaws to seat against, and slightly taper it from od to id so the jaws hit the od area. I tighten the chuck enough to leave marks for realignment.

Dont do a lot of peppermills. I work with rough turned od’s to do all drilling, then locate in the mortices to turn finish turn od’s, so that alignment is established. I use the bit cp to locate the loose end and apply light pressure against the chuck then tighten the chuck gradually, spinning the piece to see that the cp stays located.

 

[Odie]

I have a Nova G3 chuck, and others. I mostly use serrated vs dovetail. All my chucks have an “alignment mark” I etched in the body. When I mount a piece I mark the piece in that spot allowing replacing the tenon back into the same orientation. I always put a small shoulder for the top of the jaws to seat against, and slightly taper it from od to id so the jaws hit the od area. I tighten the chuck enough to leave marks for realignment.

Doug's method is very good, and I do re-chucking in very much the same manner. The indentations left by the serrated jaws are an important indicator for getting the exact repeated location for the jaws......you can feel them as you carefully close the jaws.....and, at that point, you can make minute adjustments as the jaws just begin to make contact.

Wood is not rigid, and will compress ever so slightly with pressure from the steel jaws. That, is one reason why it's important to get the same jaw pressure as the last time the wood was in the chuck. This involves some guesswork on your part, and perfection is unlikely, but is definitely a factor to consider.

-----odie-----

 

[Mike Johnson]

Anytime you remount a work piece in a chuck you will not have the same original seating of the wood work piece, you need to mark the work piece and register a reference point on the chuck to get as close as possible to the original location. When you turn a piece of green wood it is constantly moving and warping as the piece is losing mass and moisture. A machinist uses a dial indicator to mount a work piece each time no matter how good the chuck is, and they are working with a solid material that does not move like wood. If you have a center point on the tail-stock end of the work piece, this can help with aligning the work piece when you tighten the chuck jaws by apply a little pressure from the tail-stock live center on the work piece while tightening the chuck jaws after the work piece has been registered to a jaw set and mark on the work piece. Your tenon should not bottom out on your chuck jaws this is also a common error made by new wood turners that will throw the alignment off when remounting a work piece.

 

[hockenbery]

Doug and Kelly had good advice.
One problem area is the quality of the tenon and any flat area for the tops of the jaws to rest on.
A scraper won’t create as flat a flat as a cutting tool or as clean of a corner.

Turning the tenon with a Spindle gouge or other cutting tool will do the best tenons.
If you use a scraping tool be sure the tenon is free from fuzz and has a clean sharp corner.

I have had a lot of success using a perfect circle with dove tail jaws for remounting.
For the Vicmarc 120 the perfect circle is 48mm.
For small items I turn a surface to 50 mm then mm deep.
The jaws close without leaving a mark and repeat mounting is quite accurate.

A cone center in the tailstock can align the end of a spindle before the final closing of the jaws.

 

[Dennis J Gooding]

Another possible reason may be that due to misadjustment, the jaws do not grip in a perfect circle or that the circle is not centered on the spin axis of the lathe. I have encountered this problem with the pin jaws on one of my Vicmarc chucks. To see if that is the problem, turn a disk of a hard wood (to avoid the jaws digging in) and mount it in the chuck. With the lathe spinning, mark a circle with a pencil on the outer side of the disk. Now repeat, rotating the disk in the chuck 90 degrees each time. If all four circles are concentric, your chuck is in alignment. If they are not concentric, an adjustment in jaw positions is needed.

To adjust them, you need to loosen the jaw screws a bit, clamp them down lightly on a round object that is entered on the spin axis of the lathe and then retighten jaw screws. In the case of my pin jaws, I used the threaded extension of my Oneway live center. For larger jaws, I would turn a suitable diameter disk between centers, chuck it up, and bring up the live center and position the disk so that the center enters the dimple made while turning the disk.

 

[Doug Freeman]

Oneway, Nova, and perhaps others instruct that the jaws be mounted “finger tight”, the close the jaws completely with a light touch, then tighten the screws. Check the sides of the jaws for any burrs, file as needed.

 

[Daniel Miller]

I really appreciate all of the responses that you all have provided! I may have owned the chuck for 7 years but clearly I'm far from an expert in understanding how it functions! I think I've been making certain assumptions about how the chuck is supposed to behave... as an example, before now I would assume that if I had a blanks secured into a chuck and I turned it round, flattened the opposite end, etc, my assumption was that if I flipped the blank around in the chuck it would already be in-round with the chuck because I had already turned it "square" when the opposite end was in the chuck. This was a misunderstanding that I had in how a chuck operates over how I perceived that a chuck should operate. So now, at least, I'm confident that the issue isn't with a defective chuck. When you watch a video like what I linked above and see the blank turning perfectly centered after flipping it around, the guy probably did some trimming before the next video cuts in to square it all back up, but it just appears that he turns the blank around and it's magically perfectly squared to the tailstock.

 

[Mark Jundanian]

One thing to add to the above. Most chuck jaws, including Nova, are numbered. The chuck slides are also numbered. The jaws are supposed to be mounted in order, 1 on 1, 2 on 2, etc.

 

[hockenbery]

When you watch a video like what I linked above and see the blank turning perfectly centered after flipping it around, the guy probably did some trimming before the next video cuts in to square it all back up, but it just appears that he turns the blank around and it's magically perfectly squared to the tailstock.

Did not watch that video but most of the time flipping the piece centers it well enough. Perfect is unachievable, but being off small fractions of inches is pretty normal.

In this video of a demo I take two pieces off a crew center and hollow the part with no attention to the outside
I check how close they are to true. I do turn what would be the rim area a bit after the two parts are glued together but this is because they are not exactly the same diameter. If it doesn’t run close to true, I can loosen the chuck rotate it a few times. Try tightening just under tight and tap I while running until it trues up then tighten.

View: https://youtu.be/i-odbgyJvrQ

 

[William J Smith]

My two cents worth: Every so often, remove the jaws from the chuck slides and use a toothbrush or wire brush to clean off all the saw dust that may have accumulated and been compressed between the jaws and the slides.

 

[Dean Center]

Daniel, like you, I have a Nova Supernova chuck and it seems to me that when I reverse a piece and insert into the chuck with my 3" jaws, it's more off axis than it should be. The other jaw sets don't seem to be as bad. It may be that Nova produces jaws which sometimes aren't as accurate as they should be. All of the comments you've received are good ones. Follow them and you should minimize your difficulty. For me, I'm going to borrow a friend's Oneway or Vicmarc chuck and see how the results compare.

 

[Daniel Miller]

My two cents worth: Every so often, remove the jaws from the chuck slides and use a toothbrush or wire brush to clean off all the saw dust that may have accumulated and been compressed between the jaws and the slides.

I actually did a full disassemble on the SN2 a few months back because I figured after 7 years it was bound to of collected a ton of gunk on the insides and that could have been causing issues (I may have just asked the question about the chuck but it's been ongoing for some time). Imagine my surprise when it was actually pretty clean!

 

[Daniel Miller]

Daniel, like you, I have a Nova Supernova chuck and it seems to me that when I reverse a piece and insert into the chuck with my 3" jaws, it's more off axis than it should be. The other jaw sets don't seem to be as bad. It may be that Nova produces jaws which sometimes aren't as accurate as they should be. All of the comments you've received are good ones. Follow them and you should minimize your difficulty. For me, I'm going to borrow a friend's Oneway or Vicmarc chuck and see how the results compare.

That's my experiences, as far as it spinning off axis. It could be my centers that aren't as square as I think that they are. I'm going to test tonight and check, though I should have already done this.

For my pepper mills, my general process is to turn the square blank until it is round, and then I'll put it into my chuck - I think I'm using the 2" fully closed jaws? Or at least it's roughly around that size from memory. My whole thought process up to this point has been that if I'm squaring the blank to the axes with my spur drives that once I get it round and put it into the chuck that it would automatically be square to the two axes - this is where my ignorance of how these chucks should realistically work comes into play because in all the tutorial videos and etc that you watch over the years, no one ever really explains the intricacies of the hows and whys of functionality. You just see a person use a spur drive to round a blank and then they pop the blank into a chuck and it magically spins without being noticeable off-centered.

 

[hockenbery]

I have an old Nova chuck with tommy bars and encounter them often in workshops.
I find them to be more demanding for a proper tenon than dovetail or ONEWAY jaws.

I get best results for students when They turn a cylindrical tenon square to the work and cut a tiny recess with a spindle gouge or the tip of a skew to accommodate the bird’s beak at the top of the jaws. The recess should not be larger than the bird’s beak can be slightly smaller.
With that little recess the jaws can’t push the tenon out as they close. And the tenon can’t walk out of the chuck with vibration.

 

[Timothy White]

One thing to add to the above. Most chuck jaws, including Nova, are numbered. The chuck slides are also numbered. The jaws are supposed to be mounted in order, 1 on 1, 2 on 2, etc.

While this is not a bad policy, it is not an absolute. Jaw slides are numbered to fit into the scroll. When reassembling a scroll chuck ( after cleaning) it makes no difference Into which of the four slots you insert the #1 jaw slide the other three must be installed in order clockwise on a nova chuck, counter clockwise on a record power chuck.
Most chuck jaws Are turned from a solid billet then drilled. In this form the “jaw“ could be screwed onto the chuck in 4 different positions. Obviously it would be in useable. After machining the “jaw” is cut into 4pieces these pieces are numbered 1-4 clockwise on nova counter clockwise on record power, so that when mounted in order on a chuck you get the best circle. It matters NOT which jaw slide you put #1 jaw on as long as you put the other three in order. Nova jaws should always be installed clockwise Record Power jaws are installed Counter clockwise to get the best circle attainable. Jaw slide numbers and Jaw numbers have no correlation to each other. Thanks for listening.