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Nova Titan chuck

C

chrisdaniels

Joined
Mar 28, 2016
Messages
95
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6
Location
Upper Michigan
for my birthday my wife got me the titan with powergrip jaws to use on my DVR XP. I have chucked up 4 different pieces for coring and all 4 have gotten yanked right out of the jaws. I am using the correct diameter tenon and the dovetail angle is correct but do I need to use a longer tenon with those jaws or is the 1/4" still the target? I bent up one of my mcnaughton blades trying to core a 12" piece of honey locust yesterday when I got a catch somehow with the blade and it twisted up on me and yanked right out.

advice is helpful! thanks

Chris
 
chrisdaniels said:
for my birthday my wife got me the titan with powergrip jaws to use on my DVR XP. I have chucked up 4 different pieces for coring and all 4 have gotten yanked right out of the jaws. I am using the correct diameter tenon and the dovetail angle is correct but do I need to use a longer tenon with those jaws or is the 1/4" still the target? I bent up one of my mcnaughton blades trying to core a 12" piece of honey locust yesterday when I got a catch somehow with the blade and it twisted up on me and yanked right out.

advice is helpful! thanks

Chris
Click to expand...

A ¼" deep tenon definitely is not adequate and what is the "right" diameter that you are using? I would suggest that for a 12" diameter blank that you should use at least the 100 mm full dovetail jaws (4") with a tenon length of ½". If the diameter is 14 or 15 inches then use 130 mm full dovetail jaws (5"). Make certain that the shoulder of the tenon makes a sharp corner with the dovetail tenon. If it is anything less that a sharp corner then the blank will wiggle in the chuck until it breaks free. Other things include:
  • species of wood
  • dry or green
  • streingy wet wood
  • sharp coring blade
  • clearing the kerf
  • alignment of coring fixture
  • adequate mounting in chuck
 
all good possibilities, I think a combination of issues have occured, not a deep enough foot. I have been using the powergrip jaws that came with the titan since I got it assuming that it would be the best setup for coring. I have a 12" x 4.5" yellow birch bowl prepped for coring now. It started as a 15" x 5.5" but had a lot of cracks, wet over 35% but not slinging water. I'll see how it works with a 1/2" deep tenon with the powergrip jaws this time coring. I just ordered the 130mm Jaws so I can use those from now on for coring. then I will have them on my titan, 100mm jaws on my sn2, 50mm on my G3, and pin jaws on my barracuda so I think i'm set for chucks now! Thanks for the advice.

Chris
 
The powergrip jaws are different from most other Nova jaws. They have the standard dovetail-like jaw contour found in the bowl jaw series for the 1/4" adjacent to the shoulder, but deeper in, the jaws have a straight, serrated contour. If your tenon is long enough to get in farther than 1/4", the dovetail shape doesn't seem to work as well as a straight tenon. I think you have to choose one or the other section of jaw to bite with. I don't core, so I haven't any experience with the specific situation you are encountering, but on a longish hollowing job, a longer, straight tenon has worked fine for me.
 
Dean Center said:
The powergrip jaws are different from most other Nova jaws. They have the standard dovetail-like jaw contour found in the bowl jaw series for the 1/4" adjacent to the shoulder, but deeper in, the jaws have a straight, serrated contour. If your tenon is long enough to get in farther than 1/4", the dovetail shape doesn't seem to work as well as a straight tenon. I think you have to choose one or the other section of jaw to bite with. I don't core, so I haven't any experience with the specific situation you are encountering, but on a longish hollowing job, a longer, straight tenon has worked fine for me.
Click to expand...

Yes, I know about that and that is why I think that you would be better off with jaws that are full length dovetails. I am not certain, but I thought that the 100 mm and 130 mm jaws might be full length dovetail jaws. The bottom line is that coring can sometimes put a large impact type torque load on the chuck and having large diameter jaws and a long tenon are important. I also would suggest that you frequently stop to check the grip on the tenon if the wood is green or wet because the fibers will compress and cause the grip on the tenon to loosen ... and that could be at least part of the reason why you have had pieces come out of the chuck.
 
Bill Boehme said:
I also would suggest that you frequently stop to check the grip on the tenon if the wood is green or wet because the fibers will compress and cause the grip on the tenon to loosen ... and that could be at least part of the reason why you have had pieces come out of the chuck.
Click to expand...
Bill, one thing it seems nobody has mentioned is how to properly chuck the tenon to distribute the pressure evenly (especially green wood, I assume).
 
Jamie Straw said:
Bill, one thing it seems nobody has mentioned is how to properly chuck the tenon to distribute the pressure evenly (especially green wood, I assume).
Click to expand...

You mean like using the "perfect circle diameter and making solid contact with the shoulder and snugging up the jaws using the key in both locations ... and have I forgotten to mention anything?

Good catch, Jamie. Sometimes we assume that everybody already knows all of those things. It doesn't hurt to mention them anyway ... just in case.
 
Just remembered another that Lyle Jamieson says to do ... try to shake the piece loose from the jaws and then tighten the jaws again. Also, periodically check that the grip is tight or did I already say that one? Repetition is good for learning ... it's also a sign that I might be getting senile.
 
Bill Boehme said:
You mean like using the "perfect circle diameter and making solid contact with the shoulder and snugging up the jaws using the key in both locations ... and have I forgotten to mention anything?

Good catch, Jamie. Sometimes we assume that everybody already knows all of those things. It doesn't hurt to mention them anyway ... just in case.
Click to expand...
Well, those are certainly critical, but I was thinking specifically of how to orient the chuck jaws in relationship to the grain. Not putting two jaws smack on end grain, and two jaws smack on face grain. If I remember right, it's best to turn the bowl from that orientation such that (for the most part) each jaw is partly on end grain and partly on face, so the pressure is more equalized on the wood. The premise being that face and end grain compress different from each other, and doing it the first way would distort the tenon much more. Clear as mud? Great!😀
 
Jamie Straw said:
Well, those are certainly critical, but I was thinking specifically of how to orient the chuck jaws in relationship to the grain. Not putting two jaws smack on end grain, and two jaws smack on face grain. If I remember right, it's best to turn the bowl from that orientation such that (for the most part) each jaw is partly on end grain and partly on face, so the pressure is more equalized on the wood. The premise being that face and end grain compress different from each other, and doing it the first way would distort the tenon much more. Clear as mud? Great!😀
Click to expand...

OK, if it is face grain which is normally the case for bowls.
 
Bill Boehme said:
Yes, I know about that and that is why I think that you would be better off with jaws that are full length dovetails. I am not certain, but I thought that the 100 mm and 130 mm jaws might be full length dovetail jaws. .
Click to expand...


Bill you are correct the 100mm jaws are full dovetail and I am wondering if what is being called a dove tail at the top of the power grip is not just basically a bump as the 50 and 75 have. This bump is accommodated for by a small grove at the shoulder on a straight tenon. Yes that does help (the grove) on a straight tenon, but I am thinking that a complete dovetail would be better in the coring process.
 
I have the Nova powergrip jaws.......mine are not dovetail on the inside for tenons, they have the ridge lines for gripping. If you are using a dovetail tenon on those jaws, you do not have full contact with them at 1/4" length. That might explain the grip letting go. A straight tenon of 1" or even more should do the trick. If I recall correctly [without going out to the shop and measuring] the depth of the jaws will easily accommodate a 1" deep tenon.
 
well I got my 130mm jaws today and put them on the titan. I have turned and cored a 15x6 piece of hard maple and that worked fine and i'm on my second piece of the same size. one thing that I still cannot figure out is why when i'm doing large pieces no matter how much I cut I can't seem to get the darn things balanced. I normally use a faceplate and turn the outside like any other person, form the tenon and no matter what it doesn't run true. when I reverse the blanks they run out of balance so that I can't turn the lathe up past about 350rpm for a 14x6" blank. Then when I try to go through and make more cuts to get it balanced so I can turn it up no matter how much I do it won't balance out! One thing that confuses me like crazy is if I ramp it up to 600 or higher it still shakes but not nearly as bad but i'm thinking that's too fast for large bowls?
 
The need to rebalance after turning a tenon and reversing is quite understandable and actually would be out of the ordinary if you said it didn't need to be rebalanced. But, the part about never being able to get the piece balanced points to some other potential problems such as:
  • Wood isn't homogeneous especially large pieces and I frequently encounter pieces of woof that until they are turned down thin won't be in perfect balance.
  • Turning speed -- on large diameter pieces keep the speed down. I'll turn at 50 RPM if necessary. I don't worry about the speed, I'm focused on the results.
  • Bad tenon -- does the tenon diameter, length, angle, and shoulder match the chuck jaws? Perhaps the most importantly part of this is making certain that the top of the jaws and rhe shoulder oI the tenon make solid contact all the way around.
  • Loose tenon -- does the tenon get loose in the chuck? If so, figure out why.
  • If as you say, pieces never do becomes balanced and vibration really is an issue for each and every piece and you've ruled out the first four potential problems listed above then there might be some sort of machine problem.
    • Make sure that all four feet of the lathe are resting solidly on the floor and carrying about equal weight. Rocking horse lathe is the number one machine related reason for lathe vibration.
    • Check for free play in the spindle. There might be an adjustment to take out the free play.
    • Something rare, but not unheard of is a crooked spindle. My first lathe actually had a crooked spindle. When I put a chuck on the lathe, there was about 0.05" TIR. Considering the mass of a chuck, that's enough to be a serious vibration source. When I replaced the spindle it solved the problem for me.
    • Headstock not solidly locked down.
I'm sure that I've overlooked things, but these are a few things that popped into my head.
 
BTW, I don't have anything against faceplates, but unless I'm turning something really heavy, like fifty pounds or more, I don't bother with them. I generally mount a piece between centers and statically balance it ... a good way to completely bypass the vibration issue. Next, I turn it to approximate form while still between centers. Eventually, I normally turn a tenon at some point and mount it in a chuck.
 
thanks bill,
I have been wondering if my lathe is set up good on my stand good or not. I had commented on it a while ago with pictures but in the interest of solving a problem i'll post a pic with this one of my setup. the shelf below has 360 lbs of sandbags on it for weight...

ok something changed since I posted a picture last, can't get it to work
 
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chrisdaniels said:
it keeps saying file is too large
Click to expand...

Do you have any photo editing software? There are three options that I show in my preferred order, but it;s a judgement call of which to do first:
  1. Crop down to the area of interest
  2. Shrink the physical size (pixels)
  3. Compress the data (some loss of resolution)
 
Or, in other words:
  1. Use a Select tool to outline the area of interest -- then "Crop to selection" might be what you choose
  2. Resize -- that's what most programs call it -- to 200x200 or slightly less. Hopefully under "Edit" or "Image"
  3. Do a "Save as" from the "File" menu, and when the program asks if you want 100% or something else, compress until it gets below whatever our limit is (I'll look that up, sorry!) I can usually get stuff down below 150 kb for just utilitarian pics
 
Well, the limit depends on whether you're an AAW member, according to the FAQ thread, but you should be able to get it under 200 kb. I usually post 800 x 480 so it fits on the screen well. My phone makes it easy to choose from several different sizes.
 
Jamie Straw said:
Well, the limit depends on whether you're an AAW member, according to the FAQ thread, but you should be able to get it under 200 kb. I usually post 800 x 480 so it fits on the screen well. My phone makes it easy to choose from several different sizes.
Click to expand...

My mind is foggy tonight. I don't know what the limits might be for images posted in threads. I think that the rule that you are referring to is specific to gallery images. On the vBulletin forum large images posted in threads were automatically downsized. I tried an experiment about an hour ago on the old forum with an image that was 5.5 MB file size and over 5000 pixels on the long side and over 3000 pixels on the short size. It was reduced to a file size of about 550 kB. The pixel dimensions were reduced to 2415 X 1665. I'll try to find what our current settings are. They might be set at Xenforo default values.
 
 
ya it still says too large and the picture is only 1100 kb, I have posted pictures on here before quite a few times, I wonder what changed. either way I did as suggested and balanced the rough piece between centers to start it balanced and it seemed to help quite a bit. I do like using a faceplate for a 16x6" piece of hard maple because it's so heavy and it just feels safer but it turns so much easier and faster between centers that I will have to keep working with that. did 4 of those sized pieces today and cored them all i'm spent!

tomorrow I might try to do one of my burls but i'm not sure if I should do natural edge bowls or regular ones.
 
chrisdaniels said:
ya it still says too large and the picture is only 1100 kb, I have posted pictures on here before quite a few times, I wonder what changed...
Click to expand...

The maximum allowed file size for images in the discussion forum is 1000 kB (1 MB) so your image is slightly over the limit. As far as images posted in the forum goes, that's really large. On the vBulletin forum, you could upload images that were larger than the limit, but it was automatically downsized ... see post #27.

Back when we were using vBulletin 3.X there was no automatic resizing and the file size limits were much smaller.
 
OOO I think I got this one right. this is my second burl bowl but i'm not sure what I want to do with it yet. it's about 9"x4"
 

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I have had this happen too with the Titan powergrip jaws, mostly when coring dry wood. My theory has been there is less compression on dry wood than green wood. Therefore the grip is not as good and the torque from coring tears it loose. Torque from coring is far greater than using a gouge. Never happened on green wood.

I solved this on dry wood by making a longer tenon and coring at a slower speed.
 
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