Nova jaws, with true dovetails

[Dean Center]

One of our local high schools, where three local club members teach the turning component, has 3 nice lathes and 2 nice chucks. Someone donated a Nova chuck to be their third, but the other 2 chucks are Vicmarcs and the 3 guys can't deal with going back and forth between dovetail and beaked jaws. Anyone have a set of Nova bowl jaws, ideally 75mm, and with true dovetail profiles, that they'd part with? A set of 50mm might work, too. Thanks in advance for any help.

 

[Bill Blasic]

I used those beaked jaws with regular dovetailed wood for a few years until I spent a week with Richard Raffan who showed me that you don't need a 3/8" or 1/4" dovetail to hold your piece on the lathe. And since those so called beaks are actually a dovetail shape I have for close to twenty years now use those Nova jaws with an 1/8" or less dovetail on the wood without ever losing a piece of wood because of those so called beaks. Twice in my life have I lost a piece off the lathe and both of those were with dovetailed jaws but the whole dovetail separated from the piece (the piece was on the floor but the dovetail was still in the jaws, over excessive cutting was what caused it). Have them shorten the dovetail and they will be fine.

 

[John K Jordan]

Beaked vs Dovetail jaws for holding: tenon or recess?

I love the "beaked" jaws, actually small dovetails. They are easy to use and hold EXTREMELY well. I just examined about a dozen jaw sets on my various Nova chucks and some are dovetailed inside and out, some are "beaked" inside and dovetailed outside, some are straight inside and out, some are serrated inside - the point is examine the jaws carefully before deciding how to cut the recess or tenon.

Many people make a simple but problematical mistake when using internally "beaked" jaws with tenons. This method is recommended for tightening on a tenon (what some call a spigot)


Some occasionally make a similarly potentially disastrous mistake when expanding dove-tailed jaw into a recess. It is very difficult to make the dovetail exactly the same as the jaw but if erring, err on the side of less of an angle, as in the bottom sketch. The angle in the top sketch can put force on the weaker surface of the wood instead of the strong, well-supported wood at the bottom of the recess. I have witnessed bowls tossed from a lathes with this mistake. One guy did it more than once in a class.


Another thing I think most of us know: for the best holding strength make the diameter of the recess or tenon very close to the diameter of the "almost" closed jaws - this provides more surface area around the circumference than when the jaws are opened wider which can cause a weaker grip. One turner I know likes to leave a gap between the jaws when turning certain things held in a recess - he make the gap big enough to fit bowl calipers tips between the jaws to check the bottom thickness. I use other methods.

And be sure the contact ring at the bottom of the recess is flat, smooth, and clean!

Like Bill mentioned, I too rarely make a recess over 1/8" except for certain special design considerations. Even a 1/16" recess will work as long as it's made well, the recess is designed to carefully fit opened jaw diameter, and the gripping part of the jaws are sharp and not damaged or worn. (I usually cut a 2-1/16" diameter recess for 50mm Nova jaws.) I do make tenons deeper for obvious reasons.

This platter, inspired by a Frank Penta base technique, was held by a very small recess consisting of only the short curved inner arcs of the three little curved triangular shapes just outside the shallow inner decorative dome. The platter was nearly 20", heavy sapele, and this unusual recess method held securely when I turned the upper side.



It should go without saying that when turning with a minimal recess: No catches allowed!! Those prone to an occasional catch might want to use a different approach.

JKJ

 

[Dean Center]

I appreciate your replies, but the problem is a) students switch chucks from one day to the next (Vicmarc to Nova, or reverse) and b) all 3 club members are Vicmarc dovetailed jaw users. In order for the tenons to be compatible, the Nova jaws need to have true dovetails inside. The beaked jaws are designed for straight tenons.

Bill, with your 57 Nova chucks, don't you have at least one set of true dovetail 75mm bowl jaws in the back of a drawer somewhere?

 

[Bill Blasic]

About 25 actually but I will check and see what I have. If I have extra I will donate but that is not an excuse for a teacher who is teaching limit a student to learn something just because he doesn't use that equipment. Just because Nova put in its instructions what they do does not mean it is an exact science. I think it was explained very clearly how those beaked jaws work by using them differently. The only difference between the use of them compared to the Vicmarcs is a shorter tenon.

 

[Walter Mooney]

Dean, I may have a set of dovetailed 50mm Nova jaws that I can donate, but I won’t be able to check on it for about three weeks or so. If that’s not too late, I’ll send them.

I’ll keep my eye on this thread to see if someone gets it done before I can.

 

[Bill Blasic]

Surprisingly I have only 1 set of 3" jaws, sorry. But do have 31 sets of 2" jaws.

 

[Gerald Lawrence]

According to web site on the old Nova jaws the 100mm , 130mm and 75 mm power gripis the only one with inner and outer dovetail. Maybe this chart will help.
Nova Jaws Chart

 

[Dean Center]

According to web site on the old Nova jaws the 100mm , 130mm and 75 mm power gripis the only one with inner and outer dovetail. Maybe this chart will help.
Nova Jaws Chart

That's the current chart and confirms they don't have true dovetails, or any typical bowl jaws, in 75 mm. That's why I'm hoping someone out there has some older ones that are. I know they had conventional 75 mm bowl jaws in the past, and believe they were true dovetails for a period of time.

Thanks for the offer Walter. They're hard at work on bowls right now, and may be done by Christmas break. I'll let you know if we still need some.

 

[Bill Blasic]

The one set of 3" jaws I have has the full dovetail.

 

[Kirk Amidon]

I have the standard 50mm Nova jaws. There are a couple of other brands which have jaws which are interchangeable with Nova, (record is one, sorby maybe the other) but I've never been able to confirm if their standard 50mm jaws are Dovetail or not. FWIW - the other Nova jaws I have are dovetail and not the beak, I believe it is just the 50mm jaws which are the beak.

 

[John K Jordan]

Surprisingly I have only 1 set of 3" jaws, sorry. But do have 31 sets of 2" jaws.

I'm like you, with a box full of new 50mm jaws! Since another one comes with every chuck.
I'm down to 18 chucks at the moment since I gave some away.
Why so many chucks? !) I really hate to change jaws, 2) sometimes have more than one project in progress, 3) students may have chucks occupied until they return

the other Nova jaws I have are dovetail and not the beak, I believe it is just the 50mm jaws which are the beak.

I checked some of my NOVA jaws today. In no particular order (I keep multiples of some mounted), all but 2 mounted on chucks.
Measured with jaws closed with an inch caliper

Dovetailed inside and out
5" - dovetail inside and out
3.75" - dovetail inside and out
3.18" - dovetail inside and out plus grooves below internal dovetail to better hold cylinders

Dovetailed outside, grooved inside for rounds
2" dovetailed outside, grooved entire inside for cylinders, also machined to hold square blanks with minimal distortion

Dovetailed outside, can't tell inside
4" power grip jaws, 1" deep inside, appear grooved near the bottom, can't tell if they are dovetailed or beaked since a piece is mounted

Dovetailed outside, smooth inside
1" dovetailed outside, 3/8" smooth inside (pin jaws)
1" dovetailed outside, .316" smooth inside (pin jaws)

Dovetailed/beaked jaws
2" std jaws, dovetailed outside, beaked inside. A box full of these.
2" deep spigot - dovetailed outside, beaked inside, 2" deep inside, lower part grooved
2.7" dovetailed outside, beaked inside

JKJ