Oneway #2 profiled Tower jaws- expansion grip questions

[Steve Tiedman]

Howdy, I recently picked up a set of #2 profiled Tower jaws for my Oneway Talon chuck. Clamp-down/compression grab is great. I experimented on one chunk of wood in expansion mode with poor results, but I am looking for confirmation on how I blew it.


School me. My recess was a larger diameter (yikes, almost 3/8" larger dia.) than the near-round diameter as I show in the photo, and the mismatched diameter resulted in small contact patches with the jaw serrations, so I easily pried the piece of wood off the chuck with modest cutting contact. The very small amount of serrations on the outer jaw surface had little contace on the wood. (I get more fudge-factor in this regard with the dovetail outer profile on my Vicmarc's Shark jaws, so I guess I wasn't considering that.)

Tower jaw users, is that where I blew it? I need to keep that recess as small as possible to allow the closed-down jaws to make as much circumference expansion contact as possible inside the recess, correct?

Fully closed, my set of jaws measures a strong 1-15/16" outside dia. I'm thinking I should not exceed a 2" diameter recess. Maybe with a half degree of dovetail for extra pull-out resistance? Thank you for your experience with these jaws.

 

[Jamie Straw]

I'm popping this up to the top, wanting to know what folks think. My experience with expansion holds using small jaws is limited to regular #2 jaws (Not towers) on the Talon and Stronghold.

 

[Rusty Nesmith]

It doesn’t look to me like they were designed to work in expansion mode. If they were there would be a dovetail that is sharp at the edge and not that big flat spot.

 

[William Rogers]

They list an expansion mode!

 

[JeffSmith]

I have the #3 profiled tower jaws for both the Stronghold and Talon chucks. I use them in expansion mode sometimes when second turning blanks. I chuck up the warped tenon, get everything running as true as possible, then turn a shallow recess inside the bowl before turning it around to true up the tenon. I’ve never had a problem - the rim detail has a shallow groove on the largest diameter and a very shallow angled section behind - not quite a dovetail - area behind. I usually put a very slight dovetail profile on the recess and, if there’s going to be more done than just truing up the tenon (finish turning the outside to final form) I bring up the tailstock as insurance. I think the design is for a more or less straight walled recess though, and the groove is there to deform the wood for a stronger hold. Hasn’t been a problem - I haven’t lost a piece yet…the recess needs to be only about 1/8” deep.

 

[Doug Freeman]

You either did not have enough clamping force applied, or had a slight dovetail in the wrong direction. I use #2 and #3 stronghold tower jaws. Straight to a slight dove tail when using in expansion, I’ll typically have a slight dovetail just to be sure its not angled the wrong way.

Being larger then perfect circle is not an issue in my experience, its a common thing for me.

 

[JeffSmith]

Rereading the OP, I agree with Doug - recesses larger than the optimal true circle size have not been a problem in my experience; as a matter of fact, it’s more often the case than not. On larger bowls I make the recess as close to the rim as practical so there’s better access to the chuck key hole…

 

[Steve Tiedman]

Thanks Everyone. I'll experiment some more, watching my diameter and maybe a half degree of dovetail, and see how things lock in.

 

[Leo Van Der Loo]

Make sure the recess is square and clean.
Also the end of the jaws have to seat against the recess bottom.
I have used a recess to hold my turnings almost exclusively, seldom use a tenon and done so for better than 25 years.
I do not have or use the tower jaws but that should not change the holding just make sure you are not bottoming the work piece agains the chuck.