New Chuck (longish)

Re: New Chuck (longish)

Mike Schwing from Md.

>Bud, can you provide us with a photo of your two tenons on the broken pieces? I have no problems using the 2" jaws on bowls and platters up to about 12".

Only the part near the shoulder needs to be dovetailed, and the tenon should have about 3/8" to 1/2" length, but not so long as to bottom out against the jaws.

Tenons aren't a cure all for unbalanced work, so if you are creating a tenon and then trying to true an off balanced workpiece, you will have to slow the lathe down AND use the tailstock. I typically leave the tailstock in place for most of my bowl turning operations, except for when I get to the point where it gets in the way on the interior. An unbalanced workpiece can blow out of the chuck if not supported by the tailstock, but when trued, you shouldn't really be able to turn with such force that it comes off.

Re: New Chuck (longish)

John Lucas

>Bud

How long are you making your tenons. Are you putting a shoulder on the tenon to sit on top of the jaws. I've been using a Vicmarc and older Nova with # 2 jaws on bowls of this size and only remember losing a few and that was because I didn't stop the lathe periodically and retighten the jaws. Green wood gets crushed by the jaws and will loosen if you don't stop and tighten it once in a while.

Re: New Chuck (longish)

RPE

>Bud, I agree with the two previous posts. I might also add, that you can overtighten the jaws on the Super Nova and crush the wood and create a crack that will cause the wood to seperate. Use of the tail stock is a necessity for safety and reliabity. Use it as long a possible for all cuts, roughing and internal cuts. It doesn't take long to get used to working around it. Once you save a good piece by using the tail stock, it will be worth it.

I took a piece of masonite and cut a slot in it the mid range of the jaws on the Nova so when I am cutting my tenon I just slip it over the tenon to see if it is too large or small. I use dividers to mark out a rough diamater then use the masonite for final sizing.

RP

Re: New Chuck (longish)

Paul Porter in Phoenix, AZ

>Bud, are you bottoming out your tenon on your jaws? If so, try cutting a shoulder to fit the top of the jaws and leave about a 1/16" or so clearence between the bottom of the tenon and the jaws. This should give you a lot more support for your bowls and less likely to break the tenon off.

Re: New Chuck (longish)

Bud Gabaree

>I can't immediatley provide pictures (I'm supposed to be working), but I'll tell you a few more things.

First, the tenon I'm making is canted inwards about 5 degrees to match the dovetail. I am cutting a slight "indent" at the base to accomodate the top of the jaws. I have been careful to both make the tenon as thick as possible without bottoming out and to make the shoulder square for a good seat.

The bowls have been balanced without much discernible wobble, so i don't think that's the problem.

As I said, the grip on the tenon has been really good. When the bowl breaks from the tenon, its been very clean, very parallel with the grain. I didn't have this problem with my old chuck when I could leave the tenon 3" or bigger, and I rarely used the tailstock.

Any other suggestions?

Thanks again, Bud

Re: New Chuck (longish)

Bud Gabaree

>Another question; How big (diameter) are you all making your tenons? I assumed that the best grip is near the true diameter of the jaws, can I use a tenon that comes near to maxing out the upper range?

TIA, Bud

Re: New Chuck (longish)

Mike Schwing from Md.

>Oh, I didn't understand that the tenons were breaking free from the bowl. I had that occur a time or two, and I honestly think it was from clamping down too tightly on them. It has been a long long time (relatively speaking) since that has happened. I make my tenons as large as the jaws will accomodate, for both grip, and the fact that they'll go oval as the rough blank dries, and require re-truing before they will hold well for finish turning. You can enough diameter that the jaws won't grip if you start with them too small.

lose, should have said lose

Mike Schwing from Md.

>Should have said "you can LOSE enough diameter during retruing"

Re: New Chuck (longish)

W.C. Turner

>I always assumed that you get a better grip by having as small (dia.) tenon as possible. Then the jaws(IMO)grip better, in that they dont have to open as wide.

W.C.T.

Re: New Chuck (longish) *LINK*

Mark Kauder, Phenix City, AL

>Chuck,

I cannot add much to the advice given you by others, however I might suggest that you get the 4" jaws for the Nova chucks. It allows you to turn on a 4" tenon or larger.

I can't remember now, but most "Experts" suggest that when forming a tenon on dry wood, that you turn the tenon to near the minimum diameter of the jaws. This is because you will have more jaw in contact with the wood. Opening the jaws to the largest diameter the chuck will go, the jaws will only be in contact on the 8 points of the jaws.

Also get as much contact between the wood and the top of the jaws as you can. This provides the support, the tenon itself provides the grip. Leaving a gap between the top of the jaws and the wood, allows leverage to pry the wood free.

Mark


Large Nove Jaws

Re: New Chuck (longish)

Richard Allen

>Hi Bud

You could get a set of #2 Profiled Oneway Talon jaws for the chuck. These jaws are designed to hold securely over the full range of jaw openings.

What is likely happening with the dovetail jaws is separation caused by over tightening. If you think about how dovetail jaws work you will see that the more you tighten them the tighter they pull the bowl into the chuck. If you over tighten the jaws they will pull the tenon off the bowl.

The profiled Oneway jaws work on a straight tenon. They hold by crushing the tenon. The shoulder of the tenon and the face of the jaw act as additional leverage for a secure grip. If you over tighten the Oneway jaws they will push the bowl away from the chuck causing separation of that tenon shoulder/jaw face interface (weakening the grip).

I would be inclined to use the SN2 as designed and secure the bowl blank with a dovetail larger (1/2" to 3/4") than the ideal circle provided by the jaws. That larger tenon will allow for some crushing which you are likely to get with green wood. The larger tenon will also allow for ovaling of the green wood as the blank dries. Once the blank is dry you can cut a tenon slightly larger (1/8" to 1/4") than the idea circle of the jaws for finial turning.

The Oneway jaws make your life a bit easier but I don't know if they make enough of a difference that it is worth it to buy them.

Good Luck

Richard

Re: New Chuck (longish)

Dick Hines

>I have had a few bowls go flying when using a chuck. Useily it was something I did worng. Are you using the dove tail jaws. On wet wood you can cut the tenon off the bottom of a bowl if you get heavy handed with the wrench. I have the 75MM jaws and use them on tenons with no trouble.

When you cut your tenon make sure it is not to long. You want the tops of the jaws to rest on the bottom of the bowl. Most of the tenons I use are between 1/4" and 1/2". I cut them big enough so that when I return the bowl there is enough left to streighten the tenon and still have enough wood to get a good drip.

Re: New Chuck (longish)

Barry Irby

>I have both the 100 mm and the Powergrip jaw set for the Nova chucks. I had the Powergrip set first. They are also 100 mm in diameter but are at least twice as deep as the standard 100. I got the second set becasue I like to use the woodworm screw and it is too short to use with the Powergrip set. I use these more than the smaller sets. I cut a foot near the fully expanded capacity (4") and use my skew/sraper to cut a taper to accomadate the jaws, leaving a shoulder so the blank rests on the face of the jaws. I have never torn a tenon off a blank. It seems to me that the bigger tenon is in less danger of tearing off. Cutting the matching groove for jaws takes the "bite" out of them and reduces the "chisle" action. Snug them every once in a while.

I also bring the tail stock up early on. In fact, I bought an extender for the tail stock. It has a male No 2 morse taper on one end and a female on the other. It's about eight inches long and allows me to get a live center deep into a bowl and still have the tail stock back somewhat out of the way. Handy when things are unbalanced.

Never had much luck with the reverse tenon or whatever the recessed dovetail is called. If I expand the jaws enough to feel they have a good grip, I rip a shoulder off the ring. Lost one or two that way and quit doing it. Have to leave way too much shoulder on the bowl to get the small footprint I want.

Re: New Chuck (longish)

Bud Gabaree

>Thanks everyone for the input. I played around some more last night with a hickory blank. Made the tenon as large as possible while still getting the jaws around it. Also brought up the tailstock as long as possible. Worked out fine. It'll take some getting used to, but like the Marines, I'll have to adapt to the conditions.

Thanks again, Bud