Bowl Turning

Carl mitchell

Member
Messages
15
Location
Yemassee South Carolina
So I have been working on a couple different bowls but for some reason I’m only able to get the red cedar bowls to hold together and not crack. I’ve tried oak, gumball, and red cedar doing several attempts with each one. The gumball bowls are a wreck and not a single success. The oak bowls are a little difficult to turn. It they end up looking nice until they crack. The red cedar turns great and holds up well. Can anyone give me any insight into why it is this way. I will post a couple pictures for reference.
 

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Hi Carl. Welcome aboard. There are several very helpful turners here and I'm sure they will chime in. It would be good to you fill out your profile with your location so we can see what area of the country you are in. There might be someone close by that could give you some pointers, or there might be a turning club near you. My first thought is to play close attention to grain orientation in how you prepare and mount your blanks. Typically, bowls are turned from blanks that do not include the pith or center of the tree, with the grain running perpendicular to the lathe bed. Vases, urns and long narrow vessels usually have the grain parallel to the lathe bed and may include the pith, but are prone to cracks radiating out from the center that must be addressed. Google and YouTube are your friends. I'm not up to date on all the latest and best tutorials, but I bet some other folks will get you started in the right direction.
 
I'll echo Ted's welcome and advice. :wave: Like Ted said, the grain orientation plays a big role in whether the wood cracks or not. Also, some woods tend to crack more than others. In my experience, oak and some species of gum are very prone to cracking as they dry. This is especially true if the walls of the bowl are thicker than about 1/4", and even then it's a roll of the dice. Cedar, on the other hand, tends to not crack as much as a lot of other woods.

Looks like you're off to a good start. I'd suggest checking to see if there's a woodturning club in your area. Clubs are a great way to meet more experienced turners, and they are quite often eager to help mentor new guys. They can help with tool selection and presentation, sharpening, grain orientation, and form. YouTube is a good resource, but a few hours with a good turner in person is better that days worth of videos.
 
Hello Carl and welcome to the club... I'll echo Ted and Vaughn's suggestions.

In looking at your pictures, the red cedar appears to be side grain, and cedar tends to be relatively stable, especially if dried...the green bowl I'm not sure of the wood, but looks a little like an oak to me and is a partial side grain, but I think I see a pith on one side. The last picture is definitely an end grain bowl. I do very little end grain, but often will orient a bowl similar to the green one... if I have a pith mark in the bowl, a liberal dowsing with a thin CA may prevent the cracking. On the end grain bowls I do, I like to use the CA fairly liberally.

BTW, you have some nice looking bowls there.
 
Sorry about not specifying which bowls were which. The green bowl was actually from treated pine 6x6. I was using it for experience only. I may add in that I have only been turning for a couple weeks. I have a surplus of cedar available to use so I will probably stick to using it. Thank you for all the advice. I will also be turning from the side from now on
 
Carl, I'd recommend NOT turning pressure treated wood like your green bowl. The chemical preservatives in the wood are pretty toxic, and the turning/sanding process creates dust that will get into your lungs. Not a good combination. ;)
 
I also think you should avoid using pressure treated wood. I learned this lesson many years ago and will not even touch treated lumber with my hands or feet without applying gloves or shoes. I was making a pair of exterior shutters, just as a test, but began having sores on my hands that wouldn't heal. It was being caused by the chemicals used to treat the wood. The shutters were made from fir instead.

When ever I turn cedar or other soft woods I run my lathe much slower than I do when cutting hard woods. Centriugal force can be very dangerous I also stop frequently and check for cracking. Small cracks can be filled with crazy glue or the similar type used for woodworking, and then sprayed with the hardening agent. I also quite frequently wrap the outside of my rounded work with a heavy duty elastic strap to help hold it together while cutting the inside, and I always wear a leather apron and face shield in addition to my safety glasses.. If any crack becomes large, I stop convert my project into fire wood and start over. A scatter shield is now available for many lathes, but not for mine. I have considered making one, but I'm not a heavy lathe user, so I have never done it, but probably should, because it only takes once to have bad things happen.

Charley
 
Howdy Carl, welcome aboard.

Yep, its an ongoing problem.... Sometimes you turn the bowl and sometimes the bowl turns you :D Here is a short list of things I've found to help:

Agree with all of the above...

Consistent wall thickness, uneven walls (thicker bottoms) cause uneven stress and make it more likely to crack on the thinner parts. If I'm doing twice turned bowls (rough green, dry, return) the general rule of thumb is 1" of wall per 10" of diameter, although I've had mixed luck there as some bowls tend warp more than others so returning can be a trick. If turned to finish, then it depends on how dry the wood was originally. If it was pretty dry then you can get away with more variation, but if its wet then .. its trickier... the bigger the bowl blank the less likely it is to have an even moisture content.

Differential drying. If the inside of the bowl dries faster than the outside it puts the wood in compression, if the outside dries faster it puts the wood in tension which tends to pull it apart. Wood in compression is quite strong and less likely to crack. There are a lot of ways to do this, you can wrap the outside with plastic or paper, pack the bowl in shavings (leaving the center open and taking out to "air" every few days to avoid mold), and .. others. A rather dramatic example I had of this was a fairly large (17") calabash bowl I was finishing I slathered the inside with a water born poly and it started making some horrid cracking noises, realizing what I had done wrong I immediately soaked the outside with the poly and and the movement stopped.

For weird grain or other risky looking bits (pith spots, etc..) I'll sometimes saturate the area with glue (CA or white glue usually... play around with what works with your finishing routine). One larger bowls I'm planning to re-turn I'll hit the parts that are end grain with white glue and plan on just turning it away once its dry enough.

I haven't played with most of these much but there are lots of other drying methods. You can soak the bowls in a large tub of denatured alcohol (1 day per inch of thickness) which changes the drying mechanism somehow. You can use stabilizers like PEG. Boiling wood also stabilizes it (rough turn, boil 1 hour per inch of wall thickness). On turner from Hawaii soaks his work in a specific type of liquid dish soap which also acts as a lubricant when he re-turns them (he does mostly "see through" super thin stuff), and... the list continues.

As you've probably gathered by now this is an ongoing problem so you are certainly not alone :) The solutions are a varied as the turners and the wood (this is pretty common, ask three turners about something and you'll get six opinions).
 
I forgot. I know exactly where Yemassee, South Carolina is. Home of "Smokin" Joe Frasier if I remember him telling me back in the late 70's. Met him and his wife for dinner back then a couple of times.
 
One more safety tip, Carl. In addition to wearing all the protective gear, make every effort to keep your face/head out of the line of fire. That's the area around your turning perpendicular to the lathe bed where shrapnel would fly if the piece shatters.
 
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One more safety tip, Carl. In addition to wearing all the protective gear, make every effort to keep your face/head out of the line of fire. That's the area around your turning perpendicular to the lathe bed where shrapnel would fly if the bowl shatters.

Ted, I had a pepper mill explode last week... it was a glue up and the joint failed :eek::huh: , it hit me in the top of my head just above the shield... only think happened was the other glue joints failed. :D:rofl::rofl::rofl:

Carl, Heed all safety warnings... you are standing in front a piece of wood turning towards you at 400 to 3000 rpms... as they say in the drug warnings, could cause death.
 
Definitely wear the gear. I had a bodark bowl come apart on me the other day and first it caught my left forearm and then bounced off my face shield. It can will happen and when it does it is so fast you will be glad you have your protection on.
 
I’ve only had one accident so far. I was working on a bowl and instead of using my jaws inside the hollow on the bottom I tried leaving a lip for it to grab into instead. Needless to say while I was turning the lip broke off sending my bowl into my tool rest then bouncing into my chest where I caught it in my arms. Will definitely be using the expansion hold instead of the compression from now on. And thanks for all the tips guys. I will be getting my new lathe when I get home today so hopefully it will improve my turning ability since the other lathe took as much time working on it as I did in my wood. You get what you pay for haha
 
You can safely use either expansion or compression to hold bowls.. but there are tricks to both.

I would highly recommend reading the "Chucking Related" section from Doc Greens site which covers this much clearer than I can:
http://www.docgreenwoodturner.com/articles.html

Actually his whole page is quite good, recommended if you have the time :)

Since I'm here.. Alan Batty's "woodturning notes" is another great source of lots of introductory bits:
http://nebula.wsimg.com/cdb2c19af9c...EC0DC707F1FE36FCB&disposition=0&alloworigin=1

I found that via the cumberland woodturners links page:
http://www.cumberlandwoodturners.com/tips--links-and-projects.html
at a recommend from John Lucas who is another fantastic teacher/turner.
 
Yeah, when I first started I bought a STARK lathe from Walmart to see how I was going to like it. Well now that I have been turning for about 3 weeks and decided I really like it I decided to upgrade to a NOVA 2 Midi lathe. Much better quality lathe with much better designs and features. My wife is dying for me to find a way to make money with it. She has me making captive ring baby rattles and cups and such.image.jpg
 
I’ve only had one accident so far. I was working on a bowl and instead of using my jaws inside the hollow on the bottom I tried leaving a lip for it to grab into instead. Needless to say while I was turning the lip broke off sending my bowl into my tool rest then bouncing into my chest where I caught it in my arms. Will definitely be using the expansion hold instead of the compression from now on. ...

In my experience the expansion holds are as likely to slip, or more so, than the compression. Since I am cheap, and don't want to waste my prime wood on a larger lip, I often glue a block of scrap to the bottom, and turn it so that my lip is quite deep. I then cut off the scrap wood when I am done, either on the bandsaw or with a parting tool.
 
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