Heal quickly
Jeff,
Others have already answered your question about the proper size and shape for a tenon. I endorse what's been said, but I have a more basic question for you -- why are you using a chuck?
I have several chucks and I like them. However, chucks do NOT hold a bowl as securely as does a face plate. (This is true whether the face plate is screwed to the bowl blank or attached to the blank using a glue block.) Chucks are a little quicker to attach, which is a big deal if you're a production turner. For most of us hobbyists, it's not a big deal at all. The difference in time is the difference in time it takes for the CA glue (if using a glue block) to set up.
When I was first learning to turn, I was taught to use a chuck. So, I quickly bought several chucks. (I also had more than one or two blanks fly off the lathe before I learned how to use my tools properly.) While I enjoyed those turning classes and would recommend them to any new turner, I don't think that the instructors did me a favor by not teaching the proper use of a face plate.
The advantages of using a face plate are several:
- A properly installed face plate is the most secure way of attaching a bowl blank to the lathe. (You should still use tailstock support while you can.) For a new turner, one who is more apt to get a severe catch, more secure is a big deal. There's less risk of a fat lip!
- A properly installed face plate produces less vibration than does a properly installed chuck. As turners, we learn a lot of tricks to manage vibration so we can get a smooth cut. We use our free hand to "back up the cut", we use a steady rest, or we take lighter cuts than we otherwise might need to take. While these tricks work to some extent, it's better to avoid vibration in the first place by using a face plate.
- Face plates run truer than do chucks. Unlike a chuck, once you attach a blank to a face plate, you (almost) never remove it from the face plate until you part the it off. With a chuck, every time you re-mount the project back into the chuck, the blank is apt to be a little off center. That doesn't happen with face plates because you keep the project on the face plate until you're through.
- Face plates are far less expensive than are chucks. True, if you are like me, you may have several projects going at once. Which means you might need several face plates, because, as discussed above, you'll be leaving the project on the face plate until you've completed that part of your turning. Still, you can buy several face plates for the price of one chuck.
I encourage all new bowl turners to beg, borrow, or buy a copy of Lyle Jamieson's video:
Bowl Basics the Easy Way. He provides an excellent explanation of the advantages of using a face plate.
Note: I've NOT said no one should use chucks for turning bowls or anything else. I am saying face plates have their advantages as do chucks. Using one or the other is a choice. It should be an informed choice.
