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. :(:eek::mad:

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.:D

[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 :confused: 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!:eek:

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!!:D

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!:eek:

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!!:D

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 :confused:

[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:
155081

I was highly concerned about the natural edge...and equally concerned about the thickness. One catch :eek:...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. ;):)

[Roger Chandler]

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:
155081

I was highly concerned about the natural edge...and equally concerned about the thickness. One catch :eek:...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. ;):)

Hey John,

Thank you! I did not understand Windshake or Ringshake.... but it makes a lot of sense, as the layers of wood fiber would indeed be stressed by wind and other forces, and I could see separation occurring.

Boy, your skew technique where you use it like you do is something that I have not seen. If I understand you, basically the tip is used pretty much like a scraper :confused: Do you have it angled upward or just "flat" off the toolrest? The reason I ask is it seems that it would make a different in a "cutting action" resulting or a scraping off of the fibers.

All these terms are something I did not know [being exclusively self taught in woodworking and turning] but information on this and other forums are giving me an education that I did not have [ SMC online learning institute :)] and I really do appreciate the willingness of yourself and other "creekers" to help someone who like me does not have all the knowledge he needs, but nonetheless has a horrific addiction to "spinny" wood :eek::D.

Oh, buy the way......beautiful natural edge VAAAAHSSSEEE!

[John Hart]

Thanks Roger....Tell ya what...gimme a hour or so.

I know my technique is unconventional and probably goes against the grain of a lot of teachers and tutorials...but to be honest, it applies a standard tool in the way that a lot of specialty tools are designed to solve certain problems.

So...I have the day off today...I just finished the top of my new deck....I think I owe myself some lathe time. I'll go mount up a piece of junk cherry and take some pictures of what I'm talking about. who knows...maybe it'll help someone someday.

[Roger Chandler]

Thanks Roger....Tell ya what...gimme a hour or so.

I know my technique is unconventional and probably goes against the grain of a lot of teachers and tutorials...but to be honest, it applies a standard tool in the way that a lot of specialty tools are designed to solve certain problems.

So...I have the day off today...I just finished the top of my new deck....I think I owe myself some lathe time. I'll go mount up a piece of junk cherry and take some pictures of what I'm talking about. who knows...maybe it'll help someone someday.


John,

What a truly nice gesture on your part! Taking time from your deck, just to get a little lathe time in order to help a fellow "creeker" on the "SMC Online Learning Institute."

I don't think the lacquer fumes have done anything to diminish your generosity and your human kindness, no matter what John K. says!:D I will say that he has been just as helpful, and he does not use lacquer as far as I know.......:D

Hey, I love you guys!:D

[David DeCristoforo]

Boy does this give me "deja vu". I had a cherry bowl that I started turning about ten years ago. For some reason, it never got done. A few weeks ago I dug it out. The shape was very clunky bit it was still pretty thick so I figured I could reshape it. As the new shape emerged, I began to see some potential. Then I started to play with texturing the outside and I got a real direction. Ended up with the outside textured but with a band about an inch wide near the top that was polished. Looking good. So I decided to finish out the inside and polish that too. Got nearly there with the walls down to a fat eighth of an inch. But then I fell into that old trap everyone talks about of "just needing to touch up the rim" and POW! Busted it almost right in half. That was some dry cherry and brittle as can be. One touch on that thin rim was all it took.

[John Hart]

Ok...as promised, here's my little demo on this unorthodox skew technique. The objective here is to use only "the point of the skew"...and by that, I mean that the non-sharpened edge acts as a guide and the micro-miniature part of the point is the only thing in contact with your finished surface. The rest of the sharpened blade comes in contact with the discards.

It is important to limit the size of your cut for two reasons:
1. Take too big a cut and you lose your leverage.
2. Take too big a cut and you may cause unnecesary tear-out.

I have 27 pictures to post...and since I am limited to 5 per post...I'll have to spread it out.

My daughter was gracious enough to come out to the shop and be my photographer. She got good focus and turned the shutter speed up so even though the lathe is turning...she managed to freeze each shot. (pretty good for a 15 year old ;))

For the action shots...you may want to just save all the pictures to your computer so you can shoot through them and get a feel of my motion. They are all numbered from 1 to 27

This first one is just the blank mounted on a 6" faceplate. Just a piece of checked cherry. and the crack extends almost all the way to where the rim will be.
155091

This is a shot of the outer profile. Nothing fancy....just some curves
155092

And this one is the piece roughed out. Basically about a 1/2" wall following the curves to the bottom. Standard gouge and scraper work.
155093

Pics 4 and 5 show how the angle of approach will be. #4 shows the skew aligned with the outer profile. #5 shows my angle of attack.
155094155095

[Allen Neighbors]

John Hart's a lawbreaker!!!
Love it!!
I also shape my rims with a skew sometimes. Just using it as a scraper. Main thing to remember about doing this, is to cut in the Upper Left Quadrant of the opening (About 9:30 or 10: o'clock) which means that the wood is moving away from the cutting edge. If you're at 8:30 or 8:55 or so, the wood is moving toward the tool.

[John Hart]

Pic #6 shows my desired upward angle as the blade addresses the wood. Admittedly, I don't always follow that angle...I kinda roll with the punches and adjust as I go.
155096

Here's a shot after the first little cut. As you can see...it is very clean on the finished surface. I will try to acheive that all the way down.
155097

[John Hart]

Action Shots 8-12
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[Keith Burns]

"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." John Hart", Lacquer Master.

It works ! Although I have not used the skew to that extreme I do use it in a similar manner when truing up and opening. Wrks great and leaves a good finish. Will keep your method in mind for sure.

[John Hart]

Action Shots 13-17
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155107

[John Hart]

Action Shots 18-22
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155112

[John Hart]

Action shots 23-26
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And this is the final result
155117

It basically allows me to forget about the rim, as I finish off the rest of the piece.
This method is extremely safe...it works very well with NEs and odd shapes as well as standard forms

Questions and Critiques are welcome:)

[David E Keller]

Thanks to you and your daughter, John. I've never tried this, but I'm gonna try to file it away in a portion of the grey matter that gets little to no lacquer exposure. Thanks for the tip.

[John Hart]

Main thing to remember about doing this, is to cut in the Upper Left Quadrant of the opening (About 9:30 or 10: o'clock) which means that the wood is moving away from the cutting edge. If you're at 8:30 or 8:55 or so, the wood is moving toward the tool.

Good point Allen....I'm probably around 9:00-9:30 with the upward tilt of the tool. It does get problematic if the tool rest is too low.

[Roger Chandler]

Thank you, Professor Hart, of the SMC Online Wood Turning Learning Institute! [SMC-OLWTI]

John, I clicked through all your pictures in fast sequence after looking at each individual picture, and it sort of became a moving pictorial where you could see the tool movement that you did. It was as if I were looking over your shoulder.

That skew presentation is something I will keep in mind as it relates to the rim area. Your daughter deserves some kudo's as well, and make sure you tell her that I said thanks!

John, I really appreciate your tutorial. I know it took time and effort from you and your daughter.....thanks again to you both! :)

[Nate Davey]

Man, that would make a great video tutorial

[Allen Neighbors]

I love this place! SMC-OLWTI !!! Now, if I could only remember what that means...
Thanks John... I've never used the skew like that -- but I will :D

[Roger Chandler]

I love this place! SMC-OLWTI !!! Now, if I could only remember what that means...
Thanks John... I've never used the skew like that -- but I will :D

Allen,

That would be "SawMill Creek - Online Wood Turning Learning Institute"

SMC-OLWTLI

Faculty: Professor's Schlumpf, Keeton, Hart, Neighbors[yourself], Wieshapl,
and a few others that have been nice enough to help me [and others I am sure] and have increased the skill level, and shortened the learning curve for this aspiring turner/ woodworker.

I have a question.....how do you know when you graduate this institute and what constitutes a diploma? :D

[John Hart]

I have a question.....how do you know when you graduate this institute and what constitutes a diploma? :D

Graduate??!! Ha! You can check out any time you like...but you can never leave. ;):)

[Roger Chandler]

Graduate??!! Ha! You can check out any time you like...but you can never leave. ;):)

Professor Hart,

I was hoping for a diploma to hang on my wall! :D

[John Hart]

How thoughtless of me. Here ya go Roger. We'll be expecting pics of it on your wall.
155205

[Roger Chandler]

How thoughtless of me. Here ya go Roger. We'll be expecting pics of it on your wall.
155205


Professor Hart,

YOU ARE A HOOT! I realize this most "prestigious" diploma has been awarded by knowledgable experts, and has been attested to by "Alfred E. Newman" of Mad Magazine fame, so I am sure that this diploma will laud my now "expert" status, and send me forth into a world just waiting to see my expertise on display.

I just wonder what the rest of the faculty thinks about this development? :eek:

Pics will follow when I can get my son to help me post - I am glad computers and photography were not requirements of graduation, because my computer skills rival a 1st grader!

[Reed Gray]

Roger,
Most has all ready been said about scrapers. One thing though, if the blow up was caused by the scraper, in a flat/scraping cut, there is almost always a screeching/howling noise first. This is the walls of the bowl starting to flex and wobble, kind of like a soap bubble. If the vibration gets to be too much, or there is any weakness in the rim, it will catch and blow up. DAMHIKT

robo hippy

[Roger Chandler]

Thanks Reed,

I don't recall hearing the "screeching" noise you refer to, but I was doing a scraping motion from the bottom to the rim [at about 1325 rpm, as I recall]

I most likely did not realize it was a catch, because it did not feel like ones I have experienced with a bowl gouge.

You guys who are much more experienced than myself are really helping me a lot! Thanks!

One more question, what does DAMHIKT? stand for?

[Allen Neighbors]

I love this place!! But my sides hurt from laughing so much! :D:D:D:D

[John Keeton]

One more question, what does DAMHIKT? stand for?"Don't ask me how I know this." for most folks - not sure for Hart?!:confused:

[Roger Chandler]

"Don't ask me how I know this." for most folks - not sure for Hart?!:confused:

Thanks John,

I did not know that particular acrostic, but thanks for informing me!

[Harvey Ghesser]

Sawmill Creek Central....i love it!:D

[Tom Sherman]

How thoughtless of me. Here ya go Roger. We'll be expecting pics of it on your wall.
155205

Friend Hart, that signature on that diploma looks suspiciously like it might have been MOXIE induced.

[John Hart]

Friend Hart, that signature on that diploma looks suspiciously like it might have been MOXIE induced.

Guilty as charged, your honor. Ever since Hoyt's return, I've been guzzling the stuff by the gallon in an effort to understand him.;)

[Tom Sherman]

Guilty as charged, your honor. Ever since Hoyt's return, I've been guzzling the stuff by the gallon in an effort to understand him.;)

Beware my friend that stuff has residual effects...worse than Liquor or is that lacquor...now I'm confused.