When good turnings go bad

[Jim Kountz]

Well my first attempt at something hollow went from good to bad in about 2 seconds. Im guessing that my recess for the chuck wasnt deep enough or something? I posted these in hopes that maybe someone can tell me if that was the problem or what. I dont know if it was that or if my gouge just caught and dug in and thats what broke the bottom out. It happened so fast I really dont know. How deep should the recess be anyway??

[Paul Girouard]

Jim I'd guess the catch got ya , MTL just the right angle / leverage / spot to really put a load on some "weak" cross grain , At least that's what it looks like in the photo.

That recess looks to be at least 1/2" , which should be enough IMO.

Bummer eh , you had a nice shape started.

[Jim Kountz]

Well actually to be honest the photo makes the recess look alot deeper than it is. Its about 5/16" deep and close to 2-1/4 across.

[Richard Madison]

Jim,
Looks like about a 7" diameter piece, coming along nicely. You don't say what kind of wood. Depth of the recess kind of depends on the size of the piece and type of wood. Obviously deeper recess, maybe taking lighter cuts, and maybe not getting a catch would have helped this time. There is no fixed rule, other than the recess needs to be at least slightly less than the depth of the chuck jaws. I once split a piece while just tightening the chuck jaws into the recess.

With some woods, consider using a tenon and gripping from the outside, rather than gripping a recess from the inside.

Others will follow here with probably more useful advice.

[Neal Addy]

Must have been a pretty nasty catch to rip that hunk clean off the bottom. No worries. Happens to all of us.

Hollowing a HF is something that takes time. Don't get too aggressive with it. I'd have a hard time doing it with a bowl gouge.

I've always felt more comfortable with a tenon on a piece like this. Of course that doesn't mean I haven't ripped a tenon right off the piece! Been there, done that.

[Jim Kountz]

Whats a better tool for hollowing? I probably shouldnt even be attempting this yet but what the hell, thought Id try. Is the bowl gouge for the outside of the bowl only??

[Tim A. Mitchell]

Well, Jim, that is what "completed" my first bowl. I was much closer to done though, and didn't lose so much that it could not be remounted to get rid of the gash and sand it out. The green Aspen I had was a bit more forgiving.

I finished up with the scraper. I learned to be sure there is a burr on it though. Unfortuantely that was after I had finished it:( . I too was probably beyond my skills, but it never hurts to try (well, this hobby could).

I found the gouge was much faster, but the scraper was "safer" catch wise. I plan to return with the gouge, after I do a bit of spindle practice.

I like the form you had started.

[Kevin McPeek]

Its not so much the depth of the recess as it is the shape of it. If your jaws need a dovetail then you really need to have one. Just make sure you are matching the shape of the jaws to the recess.
I have turned a platter about 17.5" diameter with a recess a little less than 1/8" deep. I use a tenon about 90% of the time, I lost a few bowls with recess chucking so I stopped using it.

[Jon Lanier]

This is a guess, so help me guys if I'm wrong. Being an old newbie, could the jaw have been tightened or spread out to hard/much. Is that really a possiblity?

-Jon

[Bob Hallowell]

Jim, Don't be to hard on yourself. I think you bit off alittle to much to chew this early on. First off that looks like dry flat stock glued together and in that size it's alot harder and unforgiving. Second with that compound curve you would be getting to would prolly be best served with a heavy duty scraper or hollowing tool of some sort.

that bing said the outside is very nice you did a good job, but on that peice I would of went with a tennon also.

Bob

[Sean Troy]

I've never used a recess for chucking up a bowl or hollow form. I've used a tennon because of the much superior strength and never had one break or come off even with catches.

[Pat Salter]

This is a guess, so help me guys if I'm wrong. Being an old newbie, could the jaw have been tightened or spread out to hard/much. Is that really a possiblity?

-Jon

yes, it could be too tight, depending on the wood. one of the important things is that the inside where the jaws touch needs to be flat. As someone already mentioned, if your jaws are tapered then the sides of the recess also needs to be tapered but the bottom needs to be flat. that is where the force is transfered. The same should be if you are grabbing a tenon. the area where the ourside surface touches needs to be flat.
Hope this makes sense.

[Paul Engle]

Jim , so far i have only used a 1/2'' bg to to hf's.

[Reed Gray]

You can over tighten a chuck on a tenon, or a recess. Do tighten using each of the tightening holes for your chuck, and get it snug, but not really tight. You can break the recess with too much pressure, or get it tight to the point that if you have a catch, it will break out the foot. Some times though, it is a weak spot that a hard catch will break.

If your recess is 2 1/4 inch wide, then your chuck jaws should be about 2 1/8 inch wide. You want the fit to be as exact as possible. If you are putting 1 1/2 inch wide chuck jaws into a 2 1/4 inch recess, there will be little metal on the wood, and you don't get a good hold. The closer the fit, the more metal is on the wood, and the better it will hold.

Depth wise, you should be fine. I can core 16 inch bowls with a 3/16 inch deep recess. I do have dove tail jaws on my chuck, and the recess is also dove tailed. I think you get better hold with a dove tail than you do with straight jaws.

When I do hollow forms, I always turn them end grain. Yours was turned cross grain, which is the more common grain orientation for bowls. When turning end grain, I do use a tenon.

robo hippy

[Dick Strauss]

Jim,
The jaws will do a better job of holding if you cut the recess at least as deep as your jaws are high if you can do it. That way the bottom flat sits on the jaw flat and provides much more stability. If you don't want that deep of a recess in the turned piece, I suggest that you make some wood donuts of various thicknesses to span the gap between the shallow recess and the flat face of the jaws. The donuts should be flat on one side facing the jaws and either flat or slightly tapered towrd the center for best fit against the woodturning. You can make a few of various thicknesses and inside diameters to fit your needs.

A bowl gouge will work fine on your project as long as you move one end of the tool rest into the piece to support your gouge. Otherwise you'll be hanging off the rest more than a few inches to get to the inside bottom. A small 1/4" HSS cutter/scraper mounted in a 3/4" holder might be easier for some curves.

Good luck,
Dick

[Jim Kountz]

Id like to thank everyone for their tips and pointers. This is all really exciting to me, Im having a great time learning this here lathe business! I made another attempt at a bowl tonight and was successful to some degrees. I think Im going to go back to spindle turning for a while and practice some more basic procedures. The main reason I wanted to learn how to turn was so I could add some nice 1/4 columns to some of my casework like a chest on chest and so forth. But this bowl stuff........Man thats neat!!

[Jim Becker]

I feel a tenon is a better choice for this kind of thing than a recess, IMHO. Better support. I'll only use a recess for platters where there is good lateral support due to the nature of the piece. If there is not enough wood to provide a tenon directly, I'll use a sacrificial waste block glued onto the blank.

[Jon Lanier]

I feel a tenon is a better choice for this kind of thing than a recess, IMHO. Better support. I'll only use a recess for platters where there is good lateral support due to the nature of the piece. If there is not enough wood to provide a tenon directly, I'll use a sacrificial waste block glued onto the blank.

Okay... I've heard this talk of a 'waste block', what size should be considered ration to project. And what type of glue ought to be used... and how much?

Thanks Jim.

(or anyone else)

[Curt Fuller]

Somewhere back about 40 years ago I remember learning something that went like.."for every action there is an equal and opposite reaction". I'm guessing the dig in the hollowing was the action and the ripping out of the chuck was the reaction. If your learning curve is anything like mine, you'll do that a few more times before you get the hang of it.

[Jim Becker]

Okay... I've heard this talk of a 'waste block', what size should be considered ration to project. And what type of glue ought to be used... and how much?

Strangely enough, most of the time I use scrap 8/4 mahogany. Why? Because it was too nice to throw away and it is easy to turn very precisely when I take a wasted waste block and use it for some form of jam chuck that has to fit "exact". The bottom line is you can use just about any "stable" piece of wood. I've even used a circle cut from a nice, tight-grained 2x4 for this purpose...but when my mahogany scrap runs out someday, I'll likely switch to poplar since it's also in abundance in my shop.

You can use thick/medium CA...put the glue on one side and hit the other side with some accelerator before mashing them together. Wait a little while to be sure they are cured. You can also use regular PVA glue...it just needs to cure overnight. Do understand that some exotics don't take to glue very well and take caution with them.

[Dale Stagg]

Lookin at the middle photo. Looks like a bad catch did you in. I have had catches using tenion that don't break like you have but has dismounted from the tenion sometimes from the chuck. It then gets hard to exactly center again. I tend to get a little too aggressive at times.