Questions about turning big bowls

[Tom Jones III]

I'm a beginning turner and have exhausted my supply of 8/4 cut offs, so I stopped off at a place selling firewood on Sat. I came home with a couple huge chunks of oak - it was the only thing they had that would work, but they should do fine as my only purpose is to learn. To say they are wet and green is an understatement.

I roughed one out as best I could and mounted it between centers. I'm guessing that it probably weighed around 45 lbs. I rough turned the outside with few problems. However all I have is a 1/2" bowl gouge, is there a better tool for doing the early rough work on the outside of a monster log that is not too round?

After I got the outside roughly turned into a bowl, I cut a 3" diameter tenon but probably on 3/8" deep. I should have made it deeper, but I'm not sure that would have helped. I put it in the chuck and put the live center on it and everything was fine. My intention was to rough turn the inside so that it would season faster, then finish turn it when it was seasoned. I worked hollowing it out for a little while with the live center on then tried to turn it without the live center. It almost immediately tore a chunk out of the tenon and dropped the bowl.

How do I hollow out the inside of a big beast like this? Do I leave the live center on it and leave a column in the center until I'm done? Do I trim the middle away slowly and keep cranking the live center deeper?

Anyway, my first experience turning the big green monster was lots of fun. The mess was incredible. The view of spinning an 18" half log was impressive. I sure appreciated getting the PM 3520 lathe with almost 50 lbs of unbalanced wood spinning around!

[John Hart]

Ain't it Fun??!!:D

I really would suggest getting a bigger gouge Tom. It'll may life a little easier....nt much....but a little ;)

On big pieces like that, I like to screw the blank to a faceplate. During that intial heavy period, You really need some strength at the drive. I use Heavy duty Stainless Steel Screws too to prevent shearing the screws off.

Just my method FWIW:)

[Dick Strauss]

Tom,
not knowing your skill level, I have a few questions.

1. Is the tenon you cut square or slightly dovetailed toward the center of the bowl?
2. Did you leave a flat shoulder to help support the piece on the bottom next to the tenon?
3. Did the tenon have any bark or suspect sapwood in it?
4. Did you square up both sides before mounting by the tenon (both the tenon end and the top of the bowl)?
5. Was the bowl completely bottomed all the way around in the chuck?

These are a few questions that came to mind when I read your note. These answers might help us figure out what went wrong. I'm sure that there are other questions that might help as well. Fellow creekers, feel free to add to this list.

[Tom Jones III]

Skill level - very beginner, completed intro to bowl turning class of 3 sessions of 2 hours each. Practiced a little on my own with 8/4 kiln dried wood.

1. Square, but the wood was so wet and spongy that the tenon was not as nice and crisp as I had expected.

2. As flat as possible given conditions in #1
3. No bark or sapwood in tenon. During the class I was given a piece of mesquite to turn. It happened that the tenon had a small piece of crummy wood in one edge when I created the tenon. The instructor thought there was a chance the tenon would hold so I should go ahead and try it. The result was a spectacular throw of the bowl.

4. Fairly square & flat
5. Yes, bottom of bowl was completely against jaws of chuck.

After writing out these answers, it seems fairly obvious that the problem is diagnosed in answer #1. The wood was so soft and spongy that I had to frequently crank of the live center to make the spur center dig in farther. This is the same wood that I tried to use for the tenon. Given the massive weight of the blank, that soft spongy wood would never hold. It seems, so far, that I either mount it to a face plate or wait for it to dry as it is.

[Cecil Arnold]

Tom, I really enjoyed reading your post, as it reminds me of the problems I was having last year. Did you get through one of Steve's basic turning classes? If so, most of the questions Dick asked will be answered correctly. I think you might consider larger jaws for your chuck. If you have a Oneway Stronghold, which I suspect is the case, think about the #4 jaw set. If you are using the #2, which came on the chuck, they are too small IMHO, for the larger (over about 14") bowl work. In dealing with large blanks some kind of coring system may be something you want to consider, and yes I have one for sale. If you are interested, I have a large hackberry you can pick up for practice from the stash I told you about last month. PM me if you want the Hackberry, and I'll give you my phone number for directions.

Edit: You answered Dick's questions while I was composing my answer. The faceplate is going to be the best solution for getting the tinnion IMHO, but once you have teh tinnion you are still going to need larger jaws.

[Dick Strauss]

Tom,
a few suggestions...

1. try turning the tenon as a slight dovetail (the bottom of the tenon is widest with the top next to the bowl being slightly more narrow). This way it has to break off more wood before it lets loose.
2. try stabilizing the tenon with CA/epoxy
3. try turning the bowl down and make a new tenon in a more stable area.

Option #3 is where I'd start given your comments. If I think of more I'll add them...

[Pat Salter]

I don't know what kind of chuck you have but there are a couple of other things you might try.
1. check your chuck (say THAT three times real fast:eek: )to see how deep the tenon should be. Mine is only 3/8th's of an inch but if I make my tenon that deep so that it seats to the bottom as well as fit square at the shoulder it works good. I havn't lost too many :eek:
2. I also make the tenon as small as possible diameter. My chuck manual says it goes down to 1 7/8" so I take it down to 2". This allows more of the jaw to hold instead of just the corners of the jaw.
Let me know if that doesn't make cents. ;)

[Cecil Arnold]

Pat, I have a question. If you are turning green wood and start with a 2" tenon, what happens after the bowl is dry and you true the tenon up. Seems to me that it could wind up being smaller than 1 7/8." I don't disagree that you have more holding power with the chuck in near full contact, I only question getting it that close.

[Jim Ketron]

I use a face plate for almost all my bowls. something that large, I highly recommend it! Also you might consider getting a larger jaw set for your chuck, I use the number 3 set for large work.

[Bill Grumbine]

Hi Tom

The number of variables in this whole setup almost defy description. Oak, while not the best wood for turning, is fine practice wood, and should cut well for you. My first question is, which way was the grain going? In other words, was the grain parallel to the ways or perpendicular? Did you take baloney slices off the log or slab it so that the bowls would be sideways in the tree? Was the tenon made up of wood very close to the bark? Sometimes people will leave the cambium layer in the bowl and that can cause trouble.

A 1/2 gouge is fine for this size bowl. I have a 3/4" Glaser I will sometimes use, but my 1/2" gouge is my very favorite, and with the proper grind and the proper angle of attack, you can have that piece of wood round in no time at all.

A 3" diameter tenon is a little on the small side. The general rule for a nice looking profile is to have the bottom of the bowl roughly equal to 1/3 the top. On a bowl this size I would probably shoot for a 5" diameter tenon, figuring the bowl is going to shrink a bit as it dries and is finished. The shape of the tenon is dependent on the chuck you are using. Vicmarc and Nova chucks require a dovetailed tenon, while Oneway chucks require a straight tenon. Turning the wrong shape is inviting trouble. It is usually a simple matter to square it up for a Oneway with a parting tool, or to dovetail it with (gasp!) a skew laid over on its side!

Once you get the hang of the tool and fixing the blank to the lathe, you should be able to hollow the thing without the use of the tailstock. However, starting in on 18" bowls is inviting trouble. Six inch bowls will give you good practice, and they do not hurt as much when they hit you! I can provide you with lots more info, but I won't say anything about that here. ;)

Good luck with it.

Bill

[Charlie Plesums]

Darn. I was hoping Bill would say "oak sucks." Someone gave me some oak and cherry to try larger bowls. Cherry was great, but the oak...well... the simple answer is that they are now firewood. Having been missles, or bombs, or whatever the weapon is called.

I had convinced myself that it was the oak. Now it appears to have been the operator.

Tom, Bill is kind enough not to be commercial, but if you go to his web site, you will find the best investment of $30 if you want to learn to turn bowls.

[Chris Barton]

Since you have gotten lots of good avice about how to turn your big bowl I will only add that oak is a great wood for turning. I managed to get some white oak burls last year that were fairly big and they turned into great bowls and were a dream to turn. But, if you want really buttery smooth and easy to turn wood find some bradford pear...

[Bill Grumbine]

Darn. I was hoping Bill would say "oak sucks."

Hi Charlie

If it helps any, I was being polite! :D I avoid red oak like the plague here, especially for turning. White oak in its several varieties is not too bad, but red is just plain old not fun for me. But I have to keep telling myself, I am spoiled with the variety and quantity of wood around here. I am heating my house with wood this year, and have burned close to eight cords. Oak burns great, and while I oak poor for this season because of my turning prejudices, last week I hauled close to four cords of red and white oak out of a patch of woods where it had to be cut for maintenance of the woods. I am sure that if some people saw what went into the stove, there would be a lynching. But that is the stuff that has degraded to the point where I don't want to mess with it anymore, and there is so much more in the field!

Oak is fine for practice, but I would not turn it by choice. If you ever get up this way I will be sure to send you along with some PA grown walnut or maple, or even cherry. Now there is some nice turning wood.

Bill

[Tom Jones III]

Thanks for all the help, wow what a great forum.

The grain is perpendicular to the ways, or in other words, the bowls are sideways in the log. I got the talon chuck, so I'm using square tenons. The 3" tenon was the biggest my current jaws can handle, I'll get larger jaws soon. Thanks for the info about bottom proportions.

Initially I turned the log down with the least waste possible so the tenon was very near where the bark was. So it sounds like sometimes I will need to turn off that layer. I went back to it last night and I could tear off a chunk of the tenon with my hands. The wood is just that wet and spongy in parts. I turned it down quite a bit looking for better wood and it never got strong enough that I thought a tenon would hold.

I eventually mounted a faceplate and got the bowl hollowed out although it is now a 10" bowl after all my experimenting and turning off defects! But that is fine as all I want to do is learn from this piece of firewood. I left the walls about 1" thick. I CA glued some of the large cracks that were present in the log and worked sawdust into them. I then closed it up in a black plastic bag and sealed it up. Now I'm off to search old posts and internet search on how to know when the bowl is ready for finish turning. Thanks again for all the help.

About 6" bowls not hurting as much, I've been searching my shop looking for 8/4 cut offs and turning them into bowls. I actually made one from walnut that LOML appropriated as a new candy dish, my first "keeper" bowl! Right before I tried the big monster, I turned a 5" bowl out of a piece of 8/4 kiln dried cedar. All I wanted to do is see if I could turn the outside to match a pre-existing pattern to practice my skills. Boy, dry cedar is not much fun to turn. Anyway I was still having way too much fun, the outside went really well and I got the exact profile I wanted. I was having so much fun hollowing out the inside that I got the walls to thin in one spot. I thought, oh well I should go ahead and work on it since it is just for practice. Next thing I know there is a loud pop and the bowl is gone! The bottom is still in the chuck and I found two parts of the rim, but I still have not found the rest of it. But it was a small bowl so I wasn't using the squirrel cage. With the big monster I'm using the cage.