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Nova Pro-tek Chuck

M

Mike Zip Hamilton

Joined
Dec 19, 2018
Messages
149
Likes
92
Location
Urbandale, Iowa
I bought a new chuck with 2" jaws. I thought the new designed jaws with the dovetail grip for a spigot would be an Improvement over the parallel older jaws. Not so much; so l looked at the instructions that came with the chuck.They call for a spigot with parallel sides deep enough to seat against the back of the chuck. I have always made sure the spigot did not seat against the back, but the front of the jaws snugly seated against a flat. The back of the new jaws have a serrated section. I tried Nova's method on a small piece, and it worked fine. How do you form your spigots?
 
Depends on which chuck I am using.. I have two, one Barracuda (parallel serrated jaws) and one dovetail (7 degree) , but generally most of mine I will form with at least a very slight dovetail anyway - I can remount on second turning on either chuck, as most wood has a certain amount of compressibility, I don't worry too much about getting the perfect spigot, as long as it is true round, they generally hold pretty securely the way I cut 'em. only times Ive had a spigot pop loose was when a crack formed (ring shake or some such) or I formed the spigot in a bad spot of the wood (too close to the pith, and it separated at the growth rings) As far as the bottom goes, I do form them with a square flat spot to seat against the lip of the jaws (so it does not bottom out on the inside) - but again, I suppose the spigot is going to depend on your chuck. If you have a chuck that calls for a deeper spigot because the grip (and the flats where the spigot seats squarely) should bottom out on the inside (I don't think I've seen any that call for that before, but what do I know?) then you'd go by what your chuck requires.
 
I bought a pro-tek chuck too and when my tenon is thick enough to reach the serrated teeth, they can prevent the bowl from seating correctly. I generally make my tenons 3/16 - 1/4 deep. Haven't ever made them deep enough to reach the bottom of the jaws, so I'm not sure what advantage the serrations have. If you were turning/coring something requiring a lot of stability in the chuck, deep tenons would be useful. But for the general things I turn, The pro-tek doesn't have any advantage over the older jaws.
 
I was curious enough to look at the manual for this chuck on line and could not find those instructions you mentioned until I looked at the quick guide and I found this:

"Spigot is where the jaw contracts onto the workpiece shaped to a cylinder. This is mainly for box, goblet and vase turning (End grain items with a fair degree of overhang)."

The picture does indeed show the spigot sides parallel and the piece touching the back of the jaws which they should in this application.

If you look at the manual that comes with your chuck and find directions for a "TENON/ SPIGOT" you will find the instructions for a normal tapered tenon, even with the dovetail/ serrated jaws. It also shows the proper seating of the jaws against the workpiece.

I find that to be somewhat confusing instructions but an interesting design. I make my tenons almost touch the back of the jaws to get max contact with the taper surface. If I were to do that with these jaws, I would be crushing the outside edge of the tenon, not sure that would benefit.

I've discovered here that many turners like short tenons and these jaws would work great for them. So this design is for those turners and have the extra capability to hold boxes and other longer turnings without changing jaws...sure hope that works as designed!
 
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I own all Nova chucks. All have jaws tapered for both tenons and recesses. The only time I have had a problem with a piece coming off is if I tapered the tenon with too much of an angle. Doing this prevents the jaws from getting a bite on the whole tenon; namely the part of the tenon closest to the bottom of the bowl. As long as the tenon is angled close to the taper of the jaws I have not experienced any problems. If you err, err on the side of slightly less of an angle. However the goal is to match the taper of the tenon. I would never have the tenon bottom out. Not knowing your turning experience, I would suggest making the tenon the size which closes tightly on the wood with the jaws about a 1/4” open as that maintains a circle. Open more than that means the jaws are not a true circle and gives less jaw contact with the tenon. Also a tenon that closes the jaws completely runs the risk that the jaws will touch each other rather than just the wood, decreasing the holding power. Sorry if you already know all of this. Just trying to resolve your issue.
 
Randy, have you looked at the design of this new chuck jaws? It has a tapered outer edge but the serrated section is parallel that is past the taper. Kind of neat design if it works. Many turners make short tenons that do not use the back half of the jaws anyway. It looks like the back half and the front edge of the taper would hold onto a parallel turned spigot and there are instructions in the quick guide for using these jaws to turn boxes and other end grain turnings.

I'm not into boxes yet so I prefer tapered jaws from front to back with my tenon cut so the jaws rest firmly against the piece and a tiny space between jaws and top of tenon. Very careful to cut angle close but not always perfect and like you rarely have issues.

If short tenons and end grain turnings are what someone does then this set of jaws would eliminate needing both tapered and parallel serrated jaws, I think is the design...
 
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I do have one set of Nova Jaws with serrated insides. I can't really tell whether they have a taper or not. They are 70 mm and I believe have the designation as "bowl jaws". I haven't used them very much as I either use my smaller 50 mm or larger 100mm jaws. I've found that either the small jaws suffice or, if I'm doing a much larger piece, the 100 mm (which will accommodate a 3 1/2" tenon when opened 1/4"). Neither of these has serrated edges; just tapers both in an out. The only advantage I can se to parallel jaws with serrations is that it might be a little easier to make the tenon. I would imagine that it still holds true that the jaws should be about 1/4" open to maintain a circle. With parallel jaws, bottoming out might not be as much an issue, but I would still guess the holding power is greatest if the tips of the jaws lay against the base of the bowl rather than not. I like the Nova jaws I have and, for my use, they only fail when I'm not careful about jaw size or taper of the tenon which is rare these days as my skill has increased. I learned quickly not violate what I know is right. If I had it to do over again I'd probably invest in Vicmarc jaws. I've used them in Trent Bosch's classes and they actually do seem superior. I just wanted to make use of my old Nova jaws on my chucks so I stuck with Nova because I owned a couple of chucks from my midi-lathe days early on in turning (only about 3-4 years ago.
 
I started out with Vicmarc and have one 100 and two 120s. I've not turned with Nova chucks but I don't really see alot of difference in them and my Vicmarcs. I guess it's what you start with and works. I've looked at the Vicmarc 150 but as much as I have tried, I can't justify buying one of those monsters...

I have a set of the bowl jaws on one of the 120s that will grip the outer edge of up to a 19" bowl to true a tenon on second turning and when finishing remove and finish the tenon for the base. The other two chucks have tapered jaws that rarely need to be changed to other sizes. A faceplate is the only other mounting device I normally use. My lathe only has a 20" swing normally so these all work for me.

Just thought it was a interesting for Nova to bring two different chuck uses into the design of one set of jaws if it works.
 
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The 2" jaws that came standard with Nova chucks forever has straight sides except at the very top is what I call a very small dovetail. The instructions I believe say to make the tenon straight sided. I have never done that, I always make the tenon dovetailed. Very early on in my turning trek I spent a week with Richard Raffan were he showed that the tenon did not have to be more than 1/8" tall. I have found this to be true and use it with any of the jaws that I have especially with the Nova 2" jaws. The best way to make any chuck work is to make the tenon correctly. A correctly made tenon can be safely held with a tenon 1/16" tall, do it all the time.
 
I believe the 2" jaws referred to are those that Nova sells as 50 mm and come standard with G3 chucks and, a Pro-Tek SuperNova chuck I bought within the last year. The insides may or may not be dovetailed, but the outsides of the jaws certainly are. After purchasing the Supernova I bought 70 mm and 100 mm jaws, both having jaws which are dovetailed on both inside and out. I purchased a 75mm set of Nova "Bowl Jaws". They are serrated and parallel on the inside for tenons and dovetailed on the outside for recesses. It's a puzzle to me that Nova doesn't stick with one style or the other.

Regardless, I always dovetail the sides of my tenons (although I haven't really used the bowl jaws with parallel and serrated jaws so don't know what's best for that set) and it holds the blank extremely well. It is true that the depth of the tenon doesn't need to be very great. I usually shoot for a 1/4" , especially on larger bowls, but 3/16" is probably enough if the tenon size allows the jaws to be open about 1/4" and they are tightened down well.

I'm certainly no expert, but I have used my 100mm jaws with the dovetailed inner and outer jaw surfaces and they hold just as well and the jaw depth doesn't allow more than a 1/4" before it bottoms out. I think we all have our own preferences on technique and jaws, so whatever works.
 
More info: I had turned a 4x4 15" billet round between centers with about 1/4" dovetail on each end. When l remounted it a couple days later to cut it up to rough out some boxes, I used the PRO-TEK with tail support. The wood had been drying for about a year, but no surprise, it had warped a bit. I moved the tail stock support making the final cuts separating the 5" end. The 10" piece in the chuck became very loose. (I finished that cut with my saw.). The front of the jaws had poor contact on the piece (my bad), but since l had done this many times with my old jaws without this being an issue, I looked at the instuctions. They showed what l had been told not to do--form the tenon to seat on the bottom of the chuck. I did go to Nova's web site and found more complete instructions that showed using a short dovetail. Why did Nova lengthen the jaws to include the serrations?
 
It's unclear why companies redesign products that have worked before without problems. The serrated edges should bite into the tenon enough to hold, but I still like the dovetail jaw shape. There really isn't anything better for me. I'll have to make an effort to experiment with the serrated jaw set I have. After buying it I realized it isn't really a size that I use frequently; 75 mm I think. I either use the 50 mm or 100 mm jaws; nothing in between.
 
It's unclear why companies redesign products that have worked before without problems.

It's because people have to make "improvements" to justify their jobs!
 
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