Lyssa,
You have pretty much re-discovered the standard "recipe" for a domed rivet I published in the original Impress instructions on the artintheround website.
http://www.artintheround.com/article...he-Impress.htm
.
Here it is again for your convenience:
(By the way, for the math and trig challenged, Lyssa's 270 degree turn is simply 3/4 of a full turn)
Cut a tube 3.6 mm longer than the bead width at its widest point.
Debur the inner edge of the tube on each end.
Place the tube and bead onto the alignment peg.
Screw the cone down till it contacts the tube, but apply no force at this point.
Slide the bead to the mid point between the top and bottom, and keep it there with thumb and/or forefinger as you perform the following steps:
Screw the cone down till it is good and snug, but not enough to begin flaring the tube.
Don't forget to keep your bead near the center of the tube, away from the part that is being stretched by the cone, or it will crack. Glass does not flare very well!
It helps to imagine a clock face with twelve o'clock placed at whatever position the handle is in at the beginning of each turn.
(1) Turn the handle 3/4 turn. (9 o'clock)
(2) Flip bead and tube together, end for end. Snug it.
(3) Turn 3/4 turn.
(4) Flip. Snug.
(5) Turn 1/2 turn (6 o'clock)
(6) Flip. Snug.
(7) repeat 5 and 6 three times.
With a soft mallet such as rawhide or plastic, or a very small smooth faced metal hammer, gently tap the edges of the rivets down all around the circumference while turning the bead, until the core is tight.
There are video links there too.
http://www.artintheround.com/pages/videos.htm
Regards,
Dave