Is this safe to turn?...or burn?

[Cheryl A. Prince]

Greetings All! When I started turning about 6 years ago, I roughed out several large walnut bowls and hollow forms from a tree we took down on our property. We had a snow day today (HURRAY) and I unwrapped this 14" hollow form to find a thin crack at the largest diameter radiating about 2 to 3" up and down the form. My first thought was to fill it with turquoise and CA glue. I quickly realized that I need to turn it down to it's finished thickness before filling the crack with anything. I'm wondering if it's safe to start to finish turn this piece before stabilizing the crack somehow? Should I fill it with something first and then finish turn? With all of the accidents happening lately I don't wish to become a member of the bruised and dented club. Thanks in advance for your thoughts!

Cheryl

cracked 1.jpgcracked 2.jpg

[charlie knighton]

well, just consider if you run your lathe at 600 rpm, that's 600 rpm's at the center of your form, much faster on the outer edges where the crack has started....you can tape the outside to hollow the inside, but to redefine the outside its hope and pray

[Chip Sutherland]

I agree with Charlie on the re-turning the outside but I would try to fill the crack. You might do best to try to fill the crack from the inside as the mouth looks large enough. You are less likely to get staining if you use a sealer around the crack. When hollowing, I would use plastic wrap. If it does come apart, the plastic will contain the projectiles...I have experience with this occurrence. The downside with plastic is that you have to be diligent to get it flat/smooth so the steady rest rides smoothly. I'm assuming you are using a steady rest for a piece this size.

[Bernie Weishapl]

Ditto what Chip said. I have used saran wrap and have had maybe a 50-50 success rate. After turning for about 8 yrs now if I have bowls, hf's, etc crack they go to the burn pile especially bowls since about all of mine are used for utility purposes so cracks don't cut it.

[Jerry Marcantel]

Cheryl, I have some extra long hose clamps that I've used on a couple pieces like that and using Titebond glue. It's possible to get enough tension with the clamps to close up the gap.
If it's thick enough, turn a large groove around the OD, and segment pieces in to help make the cracks more solid if your segments are big enough and align with the cracks.....
If that's not good, I wouldn't turn it unless it can be stabilized...... ...... Jerry (in Tucson)

[robert baccus]

That's just a baby crack--not to be ignored. I suggest epoxy with a seal (hot glue or heavy metal duck tape) on the back side to act as a form before you return. Epoxy is much stronger than CA when impact is involved and cuts clean as well. You could add some tur. dust but keep the glue % high. Strapping tape might make you feel safer but is probably unnecessary here IMHO. Some stabilization of the mouth would be cool--maybe a wood cone??

[robert baccus]

Also epoxy usually does not stain like CA.

[Jeffrey J Smith]

I've filled cracks in pieces that size with epoxy - tinted, but very little filler used for strength - and had success more often than not. As Robert noted, epoxy is stronger than CA and cuts well without dulling the tools too much. I usually use hot glue to seal the back side of the crack and form a dam around the side where I'm going to pour the epoxy (use a good slow curing epoxy like West System or System 3). I put a first coat with no tint or filler to seal the edges of the crack before finishing with the tinted mix. It helps keep any tint from migrating into the surrounding wood. Bow ties, staples or other mechanical restraints could also be added if you're still wary, but I don't think they're necessary.
I always try to stay out of the firing zone as much as possible, and turn at a slower than normal speed until I'm comfortable that all is secure.

With all that said, you're the best one to determine whether it's safe or not. If in doubt, always err on the side of caution.

[Brent English]

I'm going to go "against the grain" here and suggest you burn it. Often times we get too hung up in the work invested to discard a piece that will be either unsafe to turn or artistically compromised in the end. The glue joint will show, and turquoise would add nothing to the piece decoratively. You will always loose a certain percentage of rough turned pieces. The value you gain from this piece is to look at the grain and see if the original piece couldn't have been turned in a different way to minimize cracking in the final form and to evaluate your drying techniques to see if you couldn't have done something different to prevent the crack. So my advise is to chalk it up to experience, and spend your shop time on a uncompromised piece - and one that you won't worry about failing on the lathe.

[Brian Finney]

Cheryl,

My suggestion. Given that the wood has personal value ie came from your tree it would be good to save it if poss. I’m not sure that I would turn it. You could cut the top off by hand and save the bowl beneath by shaping/sanding to thickness with an Arbotech mini grinder fitted with a saburr carbide donut .

I have used an Arbotech mini grinder http://www.arbortech.com.au/view/woodworking/mini-grinder/fitted with a carbide donut to shape and sand a large bowl - it worked well. Arbortech don’t sell the carbide donut the Saburr website below will give you a US dealer.

Saburr carbide donut http://www.saburr-tooth.com/

You will need funds if you don’t own these already.

Hope that helps

Brian

[Michael Stafford]

I'm a big chicken and seldom do I turn pieces of wood with large cracks. I had one fly apart on me and pieces smacked me in the faceshield. That was enough of that for me....

However there are some suggestions I can make that you might consider. Use pallet shrink wrap which you can obtain at big box stores and wrap the exterior in several layers stretching it tightly as it overlaps. Duct tape is a less attractive alternative and can be applied for extra strength over a layer of two of clear plastic wrap.

I have also seen other turners who inlaid bowtie patches over the cracks in a contrasting wood to a great positive effect. The appearance when turned was attractive and one of those "How did you do that" moments. You might look at Kelly Dunn's website, a Hawaiian turner who routinely salvages beautiful, rare woods with this technique.

All of that said, if in doubt, throw it out. You cannot be hurt by a piece of wood that has been discarded and if you burn it the ambience and warmth it will provide is worth something. Be safe!

[Cheryl A. Prince]

Wow! Thanks gentlemen! Your suggestions have been helpful! I am somewhat emotionally invested in this piece andwill probably try to turn it. That being said, I'm going to tint some epoxy and fill the crack. Do you think I should use my high speed carver and open the crack a little to take a little more of the epoxy, or should I just fill it as is? If I'm unsure as I'm turning (at a lower than normal speed) I'll probably take Brians suggestion and use my Arbortec (yes, I too have spent way too much money buying toys...) to turn it into a bowl of some sort. Today has to be spent running around but I will post pictures as I progress through turning this piece. I'm still open to any other suggestions. This forum is the best!

[Dennis Ford]

I have doubts that filling the crack will add significant tensile strength. A bow tie inlaid across the crack would definitely add a lot of strength. If I was emotionally invested in a piece like this; I would consider adding a bow-tie inlay before turning the outside and use one or two of the techniques mentioned above before turning the inside. My concern would be that the stresses that created that crack might not be relieved when wood was removed and the crack might expand (possibly suddenly) with bad results.

[Wally Dickerman]

That doesn't look like a crack that goes far into the wood. Depending on how thick you left the walls you can probably turn most of it away.

I suggest that you turn at a fairly low speed and do wear a facemask. Check frequently to make sure that the crack doesn't get larger..keep out of the line of fire which you should try to do anyway. Filling cracks with coffee grounds gives a much more natural look than sawdust.