Thought I would share a process for cutting the neck cope in the downtubes of a frame. This is for the connection type where the backbone welds to the top of the neck and the downtubes weld to the lower part of the neck.

This first picture shows the downtubes in the building jigs with the ends of the tubes cut square.

Next, a vertical cut is made in both tubes allowing the downtubes to move in towards the center line of the frame.

Note the two pieces of angle iron used to clamp the tubes. This is a handy tool anyone can make and also works well in the seat wishbone area.

Now a chunk of 3/4" CR round bar is put in place of the jig neck post mount where the centering cones normally mount (at least on my jig). The bar is center drilled 1/4" to take the pilot drill on a hole saw. Since you are drilling on the same centerline as your neck fixture...the cuts normally come out just right and need slight clean up to finish the joint. This neck seat was cut for a straight wall steering neck. A couple different size hole saws could have been used to fit a tapered neck.

In the picture is an air-drill and holesaw cutting the seat.

Here is a picture of the tacked assembly after the neck and backbone has been installed.

This is on a proto-type rigid frame that uses softail parts (ya got to love the irony of that). Has a 140 on the back...should take a 200. Dummy plastic engine, stock primary cover and 5-speed tranny dropped right in.