DNA Question

[Mike A. Smith]

I'm getting ready to start my first batch of DNA processing soon and I have a question. Do you leave a tenon on the rough turned bowls? If so, don't you still have a small amout of warpage of the tenon? Also, do you count the tenon in figuring the the thickness?

If not, how do you handle mounting for finish turning?

[Rob Bourgeois]

yes, yes, no...

I leave the tenon and it does warp a bit. You can usually get a good bite with the chuck. I dont worry about the tenon in my thickness. None of this is unique to DNA...wet air dried bowls would do the same thing.

[Patrick Taylor]

Don't get too complicated with the details.... thicknesses are only approximate. I sometimes will reverse-mount and round the tenon after drying, and sometimes not.

[Don Eddard]

Ditto what Patrick said. If the piece is very out of round, I'll reverse the piece and true up the tenon and sometimes the bottom of the bowl, then put it back in the chuck and do the rest.

[chris brott]

i'm pretty sure we're not talking about genetics here, so i was wondering what DNA is. and what is a tenon? does someone have pics? oh, and please don't laugh to hard, i'm a red headed step child who became a truck driver, so it's not completely my fault . seriously, i'm curious about what DNA is.

[Chris Barton]

Hi Chris,

DNA is forum jargon for denatured alcohol. A tenon is just a cylindrical protrusion that allows the wood to be griped by jaws of a scroll chuck. Welcome to SMC.

[Patrick Taylor]

i'm pretty sure we're not talking about genetics here, so i was wondering what DNA is. and what is a tenon? does someone have pics? oh, and please don't laugh to hard, i'm a red headed step child who became a truck driver, so it's not completely my fault . seriously, i'm curious about what DNA is.

Like Chris said.... and try searching here for "DNA", "alcohol", and "bowl drying". When turning wet wood, folks often soak the "rough" turned bowl in DNA to help it dry faster in preparation for final turning. There's tons of info buried here in the depths of the creek.

[Bernie Weishapl]

I agree with Patrick. Don't get to caught up with how thick this or that is. The walls of the bowls and bottom thickness is a not a science. For example bowls 12" across I leave the walls and bottom 1" thick. I generally use 10% of the size across the bowl. Leave the tenon on and you can true it up if you want. Like Patrick some I do and some I don't. It depends on how much out of shape they are. As far as the tenon goes I don't count it as far as thickness goes. If the bottom is 1" then that is what it is. The tenon will come off most time when you finish the bottom or at least will be reduced in size.

[Jim Becker]

A warped tenon is not a problem...you can simply reverse the piece between your chuck and live center (jammed together between centers) and true up the tenon before remounting in the chuck for finish work.

[Tom Keen]

I may be contrary to "best practice", but I rarely true up a tenon. I the main reason (and I could be wrong) that I occaisionally true up the tenon is if I plan on taking a piece off and then remounting it later. An out of round tenon will force you to go back and retrue all of your surfaces when you remount. I do however look for cracks on the tenon..they absorb alot of shock.. and use a little CA when I discover one. The most critical area is the front edge of you jaws..its vital that they have uniform, solid contact with the bottom of your work piece.

Good luck,
Tom

[Patrick Taylor]

The most critical area is the front edge of you jaws..its vital that they have uniform, solid contact with the bottom of your work piece.

just about the only time I true up the tenon is when I don't have good contact with the bottom of the bowl. An then, the real reason is to true the bottom of the bowl! I never unmount and remount. It never seems to work right.

[Gary Herrmann]

And don't forget that if you don't true up the tenon and you get a big ol catch that snaps it in half, you can glue it up and still finish the bowl. DAMHIKT.

[Mike A. Smith]

Thanks guys! I'd seen a lot of discussion on DNA, but had not heard anyone say anything about this.

[Robert McGowen]

And just to keep things interesting, the only time I used a tenon, I ended up with a really nice piece of firewood that was shaped like a bowl. (There were some really cool ricochets though, when the bowl would come loose.) I have never had a problem using a dovetailed recess when DNA'ing roughed out bowls though. Using the recess, you can also pretty much have the same thickness all the way through the bottom, unlike with a tenon. Just my $.02.