Collets and Tenons

I have never heard a conversation regarding the need to place a shoulder on a tenon which is to be placed in a collet as is done when using a scroll chuck. My logic tells me that there might not be a need for one for the following reasons:

1. a collet provides close to 360 degree contact with the tenon, providing greater gripping ability
2. the length of the tenon used in a collet can be made longer than the typical tenon placed in a scroll chuck thus making it more difficult (virtually impossible?) to unseat the blank in the collet

Does this sound rational? If you at times use a collet, do you place any kind of shoulder on the tenon? I ask this question with finial making in mind.

When making a finial, I usually start with by turning between centers, and turn a tenon to fit the hole it goes into. If the tenon is on the tailstock end I can check its fit with the hole. Then I will reverse it into a collet. The tenon is usually fairly short and has an undercut shoulder on it. Since it is short, the shoulder acts to increase the ability of the collet to resist catches. Also, the shoulder helps to realign the piece if I should need to take it off the lathe then replace it in the collet.

I think either way is fair game depending on your design. You are correct that the collet seems to hold things very well. I did a run of about 150 sock knitting needles last fall-- in and out, turn them around, never a slip.

I cut tenons to fit my collets almost a 100% of the time, I know it runs true, and not a problem with chucking it back up if I need to. For finials I turn between centers, add a tenon and go from there to my collet chuck.