A good quality homemade open back tenor banjo

The pot is formed in the same way as if making a salad bowl. 18 sectors are cut out of sapele at an angle of 10 degrees to form a ring with an outside diameter just a little over 9 1/2 inches. The sectors are glued with an epoxy adhesive because there is no way you will ever want to separate them. The sectors are cut so that the grain runs along the axis of the ring. That makes the job of turning down a lot easier. The glued ring is then fixed to a base plate.
Once mounted on the lathe, the pot is turned down to an outside diameter of 9 1/2 inches with a wall thickness of around a 1/2 inch (not critical)
Now a rebate is cut into the edge of the 'pot' that is just 1/8 inch into the wall thickness by 1/4 inch deep. This is to hold the tone ring. The tone ring is a simple aluminium ring formed using a ring rolling tool. The tone ring has an external diameter of 9 1/2 inches so it matches the pot O.D. Note that it isn't joined! You can see in the picture that it is being held for the photo by a piece of duct tape. There is no need to join it because it will be held shut by the head and the tension ring when they are in place
The tension ring is quite a lot of work. First a ring is formed that has an INSIDE diameter of slightly over 9 1/2inches. That is, it just slips over the tone ring and over the pot with enough clearance for the material of the head (about 10 thousandths of an inch all round). The ring is joined by rivetting a small offcut sector onto the ouside about 2" long. Because this section will be cut-away down to about half the ring height (see photo) the four rivets required are placed about 1/4 of the way up the ring. I used 1.5mm stainless steel wire.
After rivetting, the ring is cut away over the added section - this is where the tailpiece will sit and the cutout allows the strings to be set close to the head. The steeper the angle from the bridge to he tailpiece, the louder the banjo will sound. Directly opposite is where the neck is mounted and the tension ring is cut-away there too in the same way.
Eight angled slots are cut in the tension ring to locate the tension clips
Here is the completed ring
Here the tension ring, tone ring and pot are all assembled (click the picture for a larger image)

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