Turning green timber - novice question

[bassmansimon]

I get the concept of turning green timber bowls - turn to 30mm wall thickness or so, leave it on the shelf for a few months, then re-turn to the final wall thickness, removing any imperfections from warping along e way.

My question is how to re-mount a bowl? Obviously a spigot or recess at the base of the bowl can be mounted in a chuck to re-turn the inside of the bowl, but how do you mount it so that you can r-turn the outside face?

I have a few pieces of 12" square sassafras which I want to turn into platters. Approximately 80mm thick at the moment. I have a jet midi 12" lathe so that's my size restriction. I own a set of nova cole jaws (possibly thy are mini cole jaws). Would these be strong enough to hold a 12" platter to re-turn the base? I get that they are designed to do this to remove the foot of a bowl, but when things are a little warped and unbalanced, would it still work?

[bassmansimon]

Ok they are standard cole jaws and claim to hold bowls up to 10". Any simple tips for increasing the reach (safely) of cole jaws?

[dr4g0nfly]

My normal method is to;Mount on a Screw Chuck and rough turn the bowl outside, forming an oversize tenon (it will warp) on the base for the Scroll Chuck.Reverse onto the Scroll Chuck and rough turn the inside but leave a strong and long enough stubin the middle to take another tenon.When dry, I can remount between the inner tenon and tailstock, refinish the outside and reshape the tenon, reverse and cut away the inner stub and finish the inside. Then the coles jaws or other mounting system to remove the base tenon and finish off.

[bassmansimon]

Thanks. When re-mounting after drying do you moint the internal spigot in a chuck or just mount it between centres? I imagine it would be spinning more true if in a chuck.

[dr4g0nfly]

Yep, I remount it on the inside tenon on the Scroll Chuck with Tail Stock on the centre mark of the base tenon.

The inner tenon will distort the same as the bowl and base tenon, so may not run exactly true.

It will also be out of balance so the additional support makes it safer while you finish turning the outside and cut the oversize base tenon. This will the balance the bowl sufficiently to be held without any other support while to turn and finish the inside.

[bassmansimon]

Thanks sounds good

[Cliff Rogers]

Yup, that is how I do it too.

[Skew ChiDAMN!!]

Huh. I must be the odd duck in the flock, then. I actually hadn't thought of turning an inside tenon! :-

I turn a tenon at the foot of the bowl longer than needed - up to an inch longer, but usually only an extra 1/2" - turning the shoulder for the chuck as per usual. This has the effect of moving the base of the bowl an extra li'l bit away from the chuck so I can turn the outside without worrying about shaving the jaws.

I also use a long rod/dowel in the tailstock to apply pressure to the centre of the bowl just to minimise risk; I don't trust "just" a tenon with out of balance blanks.

Of course, I need cole-jaws to finish the foot. (Probably one reason I'm slowly moving into eccentric turning! :D )

[turnerted]

If you have not cut a tennon or dovetail on the inside of the bowl , all is not lost. Just mount the inside of the bowl over your chuck and hold in position with the tailstock,you may want to tap it one way or the other to get it running as true as possible , recut the tennon on the bottom and true up the outside then mount in your chuck and shape the inside.
Ted