Tennon issues and up for trade small tools

Dan Mosley

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Location
Palm Springs, Ca
Below are two bowls that i broke the tennons on today.....
Pic-1) yellow colored bowl - some type of pine or DF, using a faceplate turned the tennon and rough shape outside....then changed it around and put the tennon into my supernova with spigot jaws and turned the outside with no problem....started to hollow and "snap" then tennon tore off.....using the glue gun in the picture below (allowing 30min heat up) i reattached the tennon on this one and will let it sit overnight and try to turn again...PS this wood is very wet still...........
Pic-2) Reattached the tennon and would not hold so i used a small square block that will fit into the jaws of the supernova - using the glue gun in the pic i attached it and will try again tomm. This wood is very very dry....
I have tried Gorilla Glue and cynoacalate both and neither would hold on the above.........so im trying the glue gun to see if it works any better.
On the dry not sure why it wont hold but the wet may be that the water content migrates back rapidly and just wont hold the bond......

i did sucessfully turn 4 others today without any problem but they were different types of wood

Lastly---------i had some small tools (all are stainless steel) that i got from a guy that i bought my buffing machine from that did alot of miniature work.....i do not need them so i have them up for trade.....posted on the classified section and thought i would add a note here with pics...that if anyone wants to trade for a good blank of wood i am willing..........thanks Dan
 

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Dan for the newbie could you add a bit more to how this happened. I know it sounds stupid to ask but was it a catch or were you being very agressive or what. Just so I know what to watch out for in future. Were the tennons big enough in relation to bowl size? In the picture they seem small to me but I am a overkill kind of guy. I am looking to feed off your experience.

Thanks.
 
Thanks Rob..........below are a pic of the jaws and chuck......they max out at 2" ............i would not say the cuts are aggressive and i even tried very light cuts on the first one because i knew the wood was very wet....thanks see below
 
Dan those are some pretty small tenons for the bowl size. I try to make my tenon's at least 1/3 the diameter of the bowl. The smallest tenon I would use would be 2 1/2" on a 8" or smaller bowl. On a 12" and up bowl I use a 4" tenon. I just don't think you have enough wood there to hold by the looks of the pictures.
 
Dan those are some pretty small tenons for the bowl size. I try to make my tenon's at least 1/3 the diameter of the bowl. The smallest tenon I would use would be 2 1/2" on a 8" or smaller bowl. On a 12" and up bowl I use a 4" tenon. I just don't think you have enough wood there to hold by the looks of the pictures.

My thoughts also, and pine is really soft and will tear easily anyway... I've used a few pine waste blocks and usually eventually will tear them in half where the jaws of the chuck make an indent into the wood.

Also on your glue, I'm not sure that the glue gun has sufficient strength to handle the torque you put on it... a good wood glue will create a bond that will out last the wood around it... JMHO...
 
Bernie - Chuck

Bernie.........ya im going to look into changing to the powergrip jaws for my super nova they will go to 3 7/16, bowl jaw set are all different sizes but the larger 5" jaws are from 4 3/16-5", the 4" bow jaws are 3 1/16-3 3/4 but im going to call them first to see that i get the best jaws for the supernova i can........Any thoughts........i have a Jet 1642, 16" swing.........

Chuck........what kind of glue do you use to hold your blocks on ??
i have tried CA,Hot glue, Titebond III, gorilla glue...........anything better you or anybody using ??
 
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Bernie.........ya im going to look into changing to the powergrip jaws for my super nova they will go to 3 7/16, bowl jaw set are all different sizes but the larger 5" jaws are from 4 3/16-5", the 4" bow jaws are 3 1/16-3 3/4 but im going to call them first to see that i get the best jaws for the supernova i can........Any thoughts........i have a Jet 1642, 16" swing.........

Chuck........what kind of glue do you use to hold your blocks on ??
i have tried CA,Hot glue, Titebond III, gorilla glue...........anything better you or anybody using ??

I usually use a Titebond type of glue.. I'm not particular to a brand.. usually whatever is inexpensive and available at whatever store I happen to be in when I pick it up... I usually go to Lowe's, but have also bought at Wally-world and at my local no-name hardware store.
Just make sure you have good clean flat surfaces and I clamp overnight before trying to turn.
On the chuck jaws, I have two of the Barracuda's from PSI that I use.. the largest tenon I can clamp on is about 2 3/4.. I need to pick up another set of jaws - I think PSI calls them Nr. 3 that will allow me a larger tenon... especially now that I'm turning larger bowls.
 
...I try to make my tenon's at least 1/3 the diameter of the bowl. The smallest tenon I would use would be 2 1/2" on a 8" or smaller bowl...

I know I go against conventional wisdom on this, but I use tenons smaller than 1/3 on nearly every piece I do, and have had very few problems with things getting away from me. I've used my 50mm (2") jaws on pieces up to about 16" in diameter. But...and this is a big "but"...I only use these small tenons on good, sound wood. Pine and fir would probably not be suitable for them.

Dan, are you using a dovetail shape on your tenons? For me, that was the "aha" moment. Once I started cutting the tenon profile to match the jaws (instead of straight up and down), 99.9% of my chucking problems went away.
 
I've had good results with a 2" (about) tenon. Some times the grain won't allow it, yes..this does happen, like it or not. Usually sharp tools, lower speeds and a gentle touch solve the problem with an undersized tenon. I know someone will bash this idea but it works for me.
 
Since I began to use big tenons, I haven't had any slip off or UFOs. What's big? About 1/4 to 1/3 the size of the vessel.

If I broke a tenon, I'd toss the piece. Unless it was some expensive burl, why waste all that time? I have more wood then places to store it.

As John Jordan is fond of saying, "Life's too short to turn crappy wood."
 
I agree with Burt. Mike Mahoney and John Jordon both told me 1/4 to 1/3 is a good rule of thumb to go by. Mike told me at a demo in Denver he would never use less than a 3 3/4" or bigger tenon on a big 16" or larger bowl. He said he uses a 4" when he cores. I have never launched or broken a tenon on a bowl or HF since I started using the bigger tenons. When I was using a 2" to 2 3/4" tenon I broke a lot of them. Don't know why but both told me it may be because I hog a lot of wood quickly.
 
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