Cherry bowl came apart

[Roger Chandler]

This evening, we did not have church service due to the holiday, so I went out to the shop and thought I would finish up a cherry blank I had roughed the outside form on last Thursday.

I noticed it had cracked, so I turned the crack completely out, and proceeded to turn a bowl about 6-1/2 inches by 4 inches tall. I was leaving a section on the bottom that would be like a saucer underneath the bowl, and it was going along well.

When I had gotten the bowl about 3/4 the way hollowed, I was using a scraper to do some final smoothing and shaping [light pressure, just letting the tool take off very fine curlies] and when I got to the rim area, it just went to pieces where the end grain was, and ruined the piece.

It was going to be a nice turning, and all of a sudden it comes apart, with no apparent checking that was noticeable as I had turned the previous crack completely out.

Any ideas on what happened, so that I may avoid this in the future? Or, was it maybe just a weak piece of wood?

[David E Keller]

Sounds like the old "I'll just go back to the rim for a little touch up" maneuver.

Once you get the inside of the rim to the thickness you like with an acceptable finish, you must ignore it for the remainder of the turning. I don't proceed any deeper until I've got the rim where I want it.

If there were a ten commandment of bowl turning, I'm fairly certain that "Thou shalt not return thine tool to the rim after hollowing the middle" would make the list.

Sorry to hear about the bowl, but you're definitely not the first to do it.

[Nathan Hawkes]

Roger, I don't ever use scrapers near the rim UNLESS I am shear cutting with a very sharp scraper turned at 45 or even 60 degrees to the wood, and angled up about 25-30 degrees to the toolrest, and even then, there is sometimes chatter. The way I turn is to gradually reduce the depth of wood in sections in the center, and finish turning the surface, blending in each section as I go. As already mentioned, don't go back to your rim unless you absolutely must.

[Bernie Weishapl]

I always finish the rim before finishing the bottom half of the bowl. Or use a bowl steady to give the rim some support. As David said thou shalt not take a final cut. It always comes back to bite me anyway.

[Roger Chandler]

Bernie, Nate & David,

Someone should write that commandment on stone tablets! I have done that before, and even though I got a bit of chatter, I have never had one come apart like this one. I was using very light touch, and had the scraper angled upward off the tool rest back towards my hand. I did not have it angles at 45 degrees to the wood like Nathan mentioned.

I am wondering if this was perhaps a blank that just for some reason did not have strength or consistency of grain. I will say that I was getting some chatter before it came apart. It was at a thickness of 1/4" when it came apart, and I had planed to go maybe 1/16th thinner.

This kind of back and forth of information really does help a lot, and I want to thank you for responding to my inquiry; it is much appreciated guys!

[John Hart]

Sounds like Ring Shake. Cherry hides its cracks well and ringshake would create an environment where the piece would just come apart without notice. Just a thought.

[John Keeton]

In my limited experience, regardless of the wood, or the dryness, after finish turning the rim it will move - perhaps ever so slightly - but, it will move. When you attempt to bring the scraper to the rim, particularly with a pull cut, you will get a catch at the rim against the end grain nearly every time.

When you are getting chatter, it is proof positive that the rim is vibrating against your tool, and if the bowl has any weakness at all you will know it quickly. That crack was evidence of weakness, and as Hart said, it could have been wind shake.

Like everyone else, I try to finish the rim early on and leave it alone. On rare occasion, one can successfully push cut with a very sharp gouge to trim a rim, but it is very risky and needs to be weighed against losing the piece.

[Barry Elder]

One of the many turners who has more experience than I stated somewhere that the inside of a bowl should be turned one inch at a time to the finished thickness. If you go back to the top after the thickness below has been removed, you probably will lose it. I have a lot of respect for whoever it was that said it, because it is true from my experience with flying bowl parts!

[Roger Chandler]

I have turned for nearly 10 years. Most of my early stuff was spindle work, like table legs and furniture parts. About the fall of 2008 I began goblets and bowls, etc. In all that time, I never had one come apart on me. I did loose a couple out of the chuck and they broke, and one tenon came apart [punky wood]

I always thought that the correct thing was to make one long sweeping arc from the rim to the center of the bottom. Now one poster mentions turning an inch or so at a time I can accept that if it is the best way, and I will just have to adapt my thinking and technique, but is there consensus on this?

John K, John H. and others.....was my "long arc through the middle of the bottom" wrong, and is the stepped hollowing the right way?

[John Keeton]

Roger, first I would admit that all rules are made to be broken, so I think one just has to have a "feel" for the particular piece - sometimes you can get away with doing things that are usually forbidden. And, sometimes you think you can - and can't!

Next, let me assure you that my 6 months of bowl turning gives me no credibility on this issue. Hart was turning bowls back in the era of my grandfather - as I recall, his first lathe was steam driven, so his experience level far exceeds mine!!

On the bowls I have done, I form the outside completely, including the underside of the rim, if any, and try to do all detail work, including rough sanding. I have found it near impossible to come back and do any beads, etc. without totally re-turning the outside. Once you hollow the inside, it will move - just enough.

Then, I hog out the bulk of the inside, leaving the walls an inch or so thick. Next, I do the rim and down an inch or so to a finish cut, and then take the inside down to finish as quickly as possible with those long sweeping cuts you mention - again, to avoid movement.

I have not tried the idea of taking the entire inside down an inch at a time. Something about that makes me feel that getting the transition between each "step" would be tricky. But, then again, I have done less than 20 bowls in my long, sweeping journey as a neophyte turner!!

So, please take all of this as simply my way of doing it this month - next month it may be different!!

[Alan Trout]

Rodger,

IMHO your method is fine for hollowing but what I have found unless you are shear scraping with the scraper you are putting yourself and bowl your are turning in eminent danger of a catch. The rim is a dangerous area to have a scraper particularly when it it thin. As John mentioned you will get a little movement even in dry wood particularly at the rim.

Good Luck

Alan

[Roger Chandler]

Roger, first I would admit that all rules are made to be broken, so I think one just has to have a "feel" for the particular piece - sometimes you can get away with doing things that are usually forbidden. And, sometimes you think you can - and can't!

Next, let me assure you that my 6 months of bowl turning gives me no credibility on this issue. Hart was turning bowls back in the era of my grandfather - as I recall, his first lathe was steam driven, so his experience level far exceeds mine!!

On the bowls I have done, I form the outside completely, including the underside of the rim, if any, and try to do all detail work, including rough sanding. I have found it near impossible to come back and do any beads, etc. without totally re-turning the outside. Once you hollow the inside, it will move - just enough.

Then, I hog out the bulk of the inside, leaving the walls an inch or so thick. Next, I do the rim and down an inch or so to a finish cut, and then take the inside down to finish as quickly as possible with those long sweeping cuts you mention - again, to avoid movement.

I have not tried the idea of taking the entire inside down an inch at a time. Something about that makes me feel that getting the transition between each "step" would be tricky. But, then again, I have done less than 20 bowls in my long, sweeping journey as a neophyte turner!!

So, please take all of this as simply my way of doing it this month - next month it may be different!!

John,

Thanks for your response. That transition between stopping and starting is a hard one to pick back up on exactly, and can leave a tell-tale ridge or concave place.
I honestly don't know what happened on that bowl last night. I thought it was gonna be a pretty nifty little bowl with the saucer added to the bottom, but something went wrong that I have not experienced before. I guess I can try to be more careful [I thought I was being so] but just chalk this one up to some freak thing.

Your technique is similar to mine in the way you describe it, except for the rim being turned to completing [including sanding] which I generally just do the sweeping arc, and use very light touch for the final pass or two, sometimes with a gouge, and sometimes with a scraper. I never had a problem before, and when I have heard the "chatter" then I just used very light scraping motion.

I did make a movement last evening that went from the bottom to the rim, with the scraper, and thats when it happened.....so that was most likely my issue??????? What do you think?

John Hart mentioned some thing with the wood I had never heard of, but maybe someone who knows what it is could elaborate, and educate me, if they would be so kind......Thanks John!

I went back to Harts post, and he called it "Ring Shake"

[Roger Chandler]

Rodger,

IMHO your method is fine for hollowing but what I have found unless you are shear scraping with the scraper you are putting yourself and bowl your are turning in eminent danger of a catch. The rim is a dangerous area to have a scraper particularly when it it thin. As John mentioned you will get a little movement even in dry wood particularly at the rim.

Good Luck

Alan

Thanks Allen,

the angle of the scraper was not for a shear scrape when it broke on me... maybe coming from the bottom to the rim did create a catch, but since I was using a scraper, it did not feel the same as catches I have had with a bowl gouge, so perhaps I did not realize it for what it was

[David E Keller]

Ring shakes or wind shakes are essentially checks or cracks that occur between growth rings... Sort of like the layers of the tree are coming apart.

Apparently cherry is prone to it... I wouldn't know because it doesn't grow around here. Thank God we don't have any of that beautiful cherry growing around here!

[John Hart]

You run into ringshake (windshake) with most trees that grow tall and narrow. Severe wind, lightning, and even the act of felling can cause these separations. As the wood dries, it becomes readily apparent and easy to spot...but while it is still green...it's not so easy.

As far as your technique Roger...I think that the more you look, the more you realize that turning techniques are as unique as fingerprints...and that people actually vary their technique slightly from piece to piece..depending on the wood, desired curves, and their moods.

I don't like the rim. It's my most unfavorite part of turning because it is so vulnerable. To save me from myself, I usually use a skew...in a very unconventional manner.

Here's a piece I'm working on now:
DSC_0009.JPG

I was highly concerned about the natural edge...and equally concerned about the thickness. One catch ...and I'm done.

So...to save myself the apprehension and guarantee a successful rim, I went according to the Keith Burns addage "It Doesn't matter how you get there....just get there"

So...I want to get the rim out of the equation for the rest of my turning...and get it done first. I determine my outer profile, then I lay my skew down on my toolrest and drive the point in, at the angle of my flare...following the curve established on the outer profile.....But I only take off 1/16" at a time...driving all the way down through the neck. If it were a bowl...I'd drive down an inch or more....then when I have my rim established, I work on the rest of the piece.

I hope I described that ok. I can be quite cryptic when I don't know what I'm talking about.