Introduction: Aluminum Captive Ring on Bar

One of the first classes I took was learning to use the Metal Lathe.  Using the lathe and a bit of patience I sculpted out the form to create this cool sculpture with a free ring trapped in the middle.  This project is a great way to get familiar with using the metal lathe and is worth taking your time to practice facing, turning, plunging, parting and even a bit of undercutting.

Materials : 
- 1 inch diameter aluminum solid round bar, approximately 4-5 inches long.
- A metal lathe (find one at your local TechShop!)
- A variety of metal lathe tools including: a facing tool, a turning tool (left and right), and an undercutting tool
- Calipers for measuring
- Masking or electrical tape

Instructions :

1.) Using a pencil, divide the bar into 5 sections: the left bar cap, the left bar, the ring, the right bar, and the right bar cap.  The bar caps can be fairly short (1/4 inch to 1 inch), the bar lengths should be the longest to leave room for the undercutting step later (1 - 2 inch), and the ring should be the smallest due to it needing to be undercut later (1/4 inch or smaller).

2.) Secure the bar into the lathe jaws (don't leave the chuck in the jaws accidentally!), and set your speed to an appropriate rpm for cutting aluminum (300 - 500 RPM approximately).

3.) Double check you didn't leave the chuck in the lathe jaws.  Seriously when you get started its very easy to forget about it, and you are a danger to yourself and others in the shop if you accidentally turn on the lathe with the chuck in the lathe.

4.) Start the lathe, and using the facing tool, go ahead and face smooth the top of the bar.

5.) Next move on to the turning tool, and go ahead and turn all the way down the length of the aluminum bar and expose fresh, even metal surface.

6.) Using your guideline and the plunge tool, cut down the left and right bar sections (2 and 4) to a smaller diameter.  I used 4/10 an inch diameter, but you could probably go as low as a 1/4 inch safely.  This step will take a while, and where you will get majority of your lathe practice with this project.

7.) After the bars are cut down to their final diameter, use the undercutting tool to 'carefully' carve out the space between the middle ring section and the core bar diameter.  I recommend cutting through half way and turning the piece around in the lathe to finish the other side until it comes free.  Once the ring breaks free stop the lathe.

8.) Move the ring to one side and tape it to the end cap.  You can now use the turning tool to even out middle of the  bar.

9.) TADA! You are finished!

Hope you learned a lot, and now you have a cool sculpture for your effort.  Just remember, whatever you do: DON'T LEAVE THE CHUCK KEY IN THE LATHE.