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Woodturning (rec.crafts.woodturning) To discuss tools, techniques, styles, materials, shows and competitions, education and educational materials related to woodturning. All skill levels are welcome, from art turners to production turners, beginners to masters. |
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#1
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Forming the recess for the chuck to hold
Hi
Does the recess have to be perfect. I have a nova compact chuck. Currently no matter what I try to secure the chuck to the wood, I can tighten enough to keep the wood secure. I believe that i have the correct angle.Maybe the cut isn,t clean enough. Any suggestions Keith |
#2
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You're thinking in the wrong direction. You make the recess so that the
chuck jaws wedge themselves against the bottom of the recess, not the sides. Woodworking 090 tells you don't try to put a round peg/nail/chuck in a round hole in wood, it'll split. Thought I had sent you a reference to my page where the standard NOVA is used, but in case not, try. http://personalpages.tds.net/~upgeorge/index.html and look at the methods, using recesses. You want to keep the area where the jaw faces meet the bottom of the bowl smooth, and free of dust. Further, especially with wet wood, or weak sapwood, reinforce with water-thin CA, remembering to scrape irregularities with your skew or clean up with your pointy gouge to get a nice wedge. "Keith Young" wrote in message ... Hi Does the recess have to be perfect. I have a nova compact chuck. Currently no matter what I try to secure the chuck to the wood, I can tighten enough to keep the wood secure. I believe that i have the correct angle.Maybe the cut isn,t clean enough. Any suggestions Keith |
#3
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Thanks George. Wrong direction heh.
Thanks again. Keith "George" george@least wrote in message ... You're thinking in the wrong direction. You make the recess so that the chuck jaws wedge themselves against the bottom of the recess, not the sides. Woodworking 090 tells you don't try to put a round peg/nail/chuck in a round hole in wood, it'll split. Thought I had sent you a reference to my page where the standard NOVA is used, but in case not, try. http://personalpages.tds.net/~upgeorge/index.html and look at the methods, using recesses. You want to keep the area where the jaw faces meet the bottom of the bowl smooth, and free of dust. Further, especially with wet wood, or weak sapwood, reinforce with water-thin CA, remembering to scrape irregularities with your skew or clean up with your pointy gouge to get a nice wedge. "Keith Young" wrote in message ... Hi Does the recess have to be perfect. I have a nova compact chuck. Currently no matter what I try to secure the chuck to the wood, I can tighten enough to keep the wood secure. I believe that i have the correct angle.Maybe the cut isn,t clean enough. Any suggestions Keith |
#4
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Keith
I have found that I get better results when I use a tennon instead of a recess - the chuck can get a bettr bit in the compression mode versus the expansion mode - you may want to try using a tennon and then jam chucking the bowl to finish the bottom Ray "Keith Young" wrote in message ... Hi Does the recess have to be perfect. I have a nova compact chuck. Currently no matter what I try to secure the chuck to the wood, I can tighten enough to keep the wood secure. I believe that i have the correct angle.Maybe the cut isn,t clean enough. Any suggestions Keith |
#5
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I have found that I get better results when I use a tennon instead of a
recess - the chuck can get a bettr bit in the compression mode versus the expansion mode - you may want to try using a tennon and then jam chucking the bowl to finish the bottom With my Nova chuck (although the original author has a compact version), I get MUCH better grip in expansion vs. compression. Don't get me wrong, the compression is great, but in expansion, I get more solid holding with less visible marring of the wood. I rarely, if ever, make the recess (or a tenon, for that matter) the full depth of the jaw's dovetail. I just make sure that the angle of the recess/tenon is such that the farthest point of the dovetail is what makes contact first, and then things go great. Good enough, in fact, that a year or so ago when I first tried purpleheart and made a rather stupid mistake, I broke the tenon off of the piece before the grip of the chuck gave up. steve |
#6
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I'm just the opposite. I've never had very good success with the nova chuck
in expansion mode. I turn everything with a tennon and never had one come loose. I've broken the wood with a catch using both methods so neither seems to have an advantage there for me. Do you think our different experiences are related to our turning methods or just coincidence? Tony Manella ndd1"at"prolog.net (remove "at") http://home.ptd.net/~ndd1/ Lehigh Valley Woodturners http://www.lehighvalleywoodturners.com/ "Steve Wolfe" wrote in message ... I have found that I get better results when I use a tennon instead of a recess - the chuck can get a bettr bit in the compression mode versus the expansion mode - you may want to try using a tennon and then jam chucking the bowl to finish the bottom With my Nova chuck (although the original author has a compact version), I get MUCH better grip in expansion vs. compression. Don't get me wrong, the compression is great, but in expansion, I get more solid holding with less visible marring of the wood. I rarely, if ever, make the recess (or a tenon, for that matter) the full depth of the jaw's dovetail. I just make sure that the angle of the recess/tenon is such that the farthest point of the dovetail is what makes contact first, and then things go great. Good enough, in fact, that a year or so ago when I first tried purpleheart and made a rather stupid mistake, I broke the tenon off of the piece before the grip of the chuck gave up. steve |
#7
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I'm just the opposite. I've never had very good success with the nova
chuck in expansion mode. I turn everything with a tennon and never had one come loose. I've broken the wood with a catch using both methods so neither seems to have an advantage there for me. Do you think our different experiences are related to our turning methods or just coincidence? Without having seen each other's turning methods, it's hard to say. : ) I should say that the difference I get isn't so much because the chuck itself grips better in either mode, but because when I turn in expansion, I usually have better geometry on the wood. Like you, I've had the tenon break before the chuck gave out - but the way I use it in expansion, there's typically more wood behind the grip, so to speak, and I've never had a break that way. steve |
#8
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Hi Steve,
When I have a failure in expansion mode it is usually the wood that breaks out rather than anything with the chuck. Must just be my style of turning. Tony Manella ndd1"at"prolog.net (remove "at") http://home.ptd.net/~ndd1/ Lehigh Valley Woodturners http://www.lehighvalleywoodturners.com/ "Steve Wolfe" wrote in message ... I'm just the opposite. I've never had very good success with the nova chuck in expansion mode. I turn everything with a tennon and never had one come loose. I've broken the wood with a catch using both methods so neither seems to have an advantage there for me. Do you think our different experiences are related to our turning methods or just coincidence? Without having seen each other's turning methods, it's hard to say. : ) I should say that the difference I get isn't so much because the chuck itself grips better in either mode, but because when I turn in expansion, I usually have better geometry on the wood. Like you, I've had the tenon break before the chuck gave out - but the way I use it in expansion, there's typically more wood behind the grip, so to speak, and I've never had a break that way. steve |
#9
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Keith Young wrote:
Does the recess have to be perfect. I have a nova compact chuck. Currently no matter what I try to secure the chuck to the wood, I can tighten enough to keep the wood secure. I believe that i have the correct angle.Maybe the cut isn,t clean enough. Keith, some more information might be helpful, like the type of wood, its green/dry status, bowl size, and the diameter and depth of the recess. Does the bowl fall off of its own accord, or does it take a catch In my experience the diameter of the recess is more important than the angle of the dovetail. I say that because I do a lot of first fixings into a shallow hole drilled with a forstner bit, so I have no dovetail at all. Remember that the jaws have only one true diameter, that is when they form a true circle. When expamded beyond that diameter they grip only at the center of their arc, and at smaller diameters they grip at the ends of their arc. One other tip is to make sure the chuck is clean of dust and operates smoothly and easily. If it gets gummed up, a lot of the power you apply to the key is expended overcoming friction, and it is difficult to get any feel for how tight the jaws are. You really shouldn't have to crank too hard on the key to hold a bowl. I periodically blow all the sanding dust out of the chuck and give the threads a little graphite lubricant. The jaws should then operate with just the lightest touch. For final fixing I make the dovetail with a small detail gouge so the edges are nice and clean. The bottom of the recess is finished with a flat scraper, the finished shape of the recess erring towards concave. -- Derek Andrews, woodturner http://www.seafoamwoodturning.com Wedding Favors ~ Artisan Crafted Gifts ~ One-of-a-Kind Woodturning |
#10
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Only if you don't bottom it. I assume you are doing so (as I do also) with
your first fixing. The jaws don't need to "grip" anything unless you're using them in a non-dovetail recess. Check the pin jaw setup at the pages I referenced. Even there, the difference is in the bottoming. "Derek Andrews" wrote in message ... In my experience the diameter of the recess is more important than the angle of the dovetail. I say that because I do a lot of first fixings into a shallow hole drilled with a forstner bit, so I have no dovetail at all. SNIP You really shouldn't have to crank too hard on the key to hold a bowl. |
#11
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Follow-up. The pin jaws on the NOVA are circular at 1.125", the maximum
depth of dovetail is 3/16. Quick math, verified after getting back from the ambulance garage shows a maximum jaw edge only contact area of .663 sq inches. Jaw faces are slightly greater than .25 broad, offering a contact area of 2.76 sq inches. In reality, reduce each by about 15% for gaps. More to the point, the mechanical advantage of the .5625 arm resists movement much better than the .1875 at nearly right angles to it, especially when the force of cutting is nearly perpendicular to it when running from bottom to rim or rim to bottom. I would never recommend an edge presented perpendicular to the axis of rotation. Bottom those jaws, that's where the money is. "George" george@least wrote in message ... Only if you don't bottom it. I assume you are doing so (as I do also) with your first fixing. The jaws don't need to "grip" anything unless you're using them in a non-dovetail recess. Check the pin jaw setup at the pages I referenced. Even there, the difference is in the bottoming. "Derek Andrews" wrote in message ... In my experience the diameter of the recess is more important than the angle of the dovetail. I say that because I do a lot of first fixings into a shallow hole drilled with a forstner bit, so I have no dovetail at all. SNIP You really shouldn't have to crank too hard on the key to hold a bowl. |
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