Mahogany Bowl Mishap

if I had to guess, barry, the grain is running perpendicular to the ways rather than parallel to it - mahogony is not strong in cross grain shear - just don't be so agressive in hollowing - if the grain were running parallel to the ways, 2" would have been plenty strong.

just my 2 cents

bill N (been there, done that, sadly, more than once)

It maybe. Your problem sounds like one my grandson and I ran into today. We were turning an 11" bowl out of cedar with a recess to put an expansion chuck in. The recess broke out after we had reversed the bowl and locked the bowl on the expansion chuck. What we did was find center of of the recess and remounted it between centers, but used the chuck on the headstock. Turned a new recess a bit larger with a bit thicker sidewall. Worked well.

Deb

Yep. You're right, side-grain bowl. But, it wasn't aggressive hollowing that caused the problem, just a @#$%* catch. Gotta learn how to use that Ellsworth grind.

Barry

Barry, I assume that right up to the point where you had the "catch" your tenon was doing it's job. It was not a question of how big the tenon was or whether you should have used a mortise. The "problem" was the "catch. If you intend to continue having "catches" then I suggest you get bigger jaws for turning 10 inch bowls. If not then I suggest you analyze exactly what caused your catch and do everything you can to avoid presenting the tool to the wood in that fashion again. Makes more sense than getting a "Tim the Tool Man" set of jaws for a very small bowl. IMHO of course......I could be wrong...... ;^)

=====> Don't listen to him, Barry! Now you have a half-ways decent excuse to buy another chuck!!! Every real turner should have three or four at least.*G*

Leif

I'm just getting back to turning - have been doing it for 30 years on-off busy in metal most of the time now - but have to do a large handle for a 2" size wrench of 1/4" steel I made for my Uncle.

I suggest that a 5:1 ratio did it - consider a small pressure is amplified

5X to the smaller diameter or 25x of the cross sections.

It might be worse - have to consider the Math ... surface pi*D 6" vs 30 same ratio consider cross section - pi*r^2 3.14 vs 78.5 < large ratio.

Sometimes we overlook the forces at work. Maybe soaking the tenon in the first (or now) with thin CA might fortify the grain.

Mart> Yep. You're right, side-grain bowl. But, it wasn't aggressive hollowing

"Leif Thorvaldson" wrote in news: snipped-for-privacy@corp.supernews.com:

Now I can understand how I might use two chucks on a bowl. Explain three or four, please.

Patriarch

*SIGH!* Of all people, Patriarch, I would have believed you would immediately comprehend the significance of possessing more than two chucks. To explain: I have more than one bowl gouge (different sizes, eh?), more than two clamps (different sizes, different clamping features, eh?), etc. Now you see where I am going with this? Since I now have more than two chucks and can only use two at the most on my single lathe -- it stands to reason that I need an additional lathe to go with the chucks. QED, eh?Omigawd, stop me someone!! And, I am even starting to sound like a Canadian, eh? *G*

Leif

I am uncertain if it translates over to your situation but some time back I recall reading that if you use a faceplate the largest diamter would be no more than 3 X the isze of the faceplate, i.e., a 3" faceplate would allow the turning of a 9" diameter bowl. Also, as others have mentioned, a large factor in the determination of the size of the tenon would be the nature of the wood itself. Hope all turns out well.

thanks, Bill.. that's exactly what I was trying to say in the prior post, but the words weren't forming... I need more coffee!

mac

Please remove splinters before emailing

He probably has 2 or 3 soaking in LDD to prevent jaw cracks....

mac

Please remove splinters before emailing

Hi Mac

They better not be those cheap ones or they be all rusted together,....... come to think of it, that would make the LDD just right for wood staining at the same time ?? yes?? no ??

Have fun (at the expense off) and take care Leo Van Der Loo

mac davis wrote:

====>Scoff all you like, gentlemen! I have had one chuck gripping the tenon of the bowl that I immersed in LDD. I kept the chuck out of the LDD solution and just dangled the bowl in it while I was busy turning another bowl mounted on a second chuck. As to chucks 3 & 4, they are only figments of my imagination. Since I am no longer married, I have no good woman to agree with me that I need more chucks and thereby, allow me to spend the money. You guys are so lucky! *G*

Leif

Barring tremendous catches, I think a 2" tenon would be perfectly adequate for a 10" bowl.

I think I have gotten myself out of this mess. Last night, I used medium viscosity CA glue and re-attached the tenon to the bowl. I finished hollowing without mishap tonight. I have power sanded the exterior and interior of the bowl. Now all that remains is to reverse the bowl and turn the foot, which should be fairly straight forward. God bless the guy(s) who invented CA glue.

Barry

====>CA courtesy of the NASA Space Program. You'd think they might use some of it to hold their insulation and tiles on, though!! Only a billion dollars spent so far on solving the problem and they still come loose!

Leif

"Leif Thorvaldson" wrote

I wonder what type of duct tape they could have come up with for a billion dollars.

"Duck" is the proper term, and I think the Military let the spec for it during WWII. Don't use it for taping your HVAC ducting. Much better stuff out there for that.

Tried to avoid my oft-expressed opinion here, so as not to sound a Leif (LDD anyone?), but here it goes again. The width of the shoulder that the jaws ride against, and the proper registry against the shoulder are the most important factors in holding the piece. That way it isn't just the tenon length you have to lever against, but the shoulder, too. Since the shoulder is perpendicular to the angle of a proper cut, and extends farther from the point of rotation, it has the greatest mechanical advantage.

Weakness of destructive grips - non wedge types - is that they are as likely as not to push the nose of the jaws out of register with the shoulder as into. With a dovetail, the wedge draws tight up against the shoulder, whether that is an innie or an outie.

Then there's the tailstock issue....