Homemade Headset Cup Removal Tool

Is the copper resilient enough if you have an ornery old crusty cup? I used a 1" dia. maple dowel for a 1" head tube.  It worked perfectly, and being wood it won't harm any frame materials, including bamboo.  If ya need a larger dia., then it can be made like your copper one, but the trick is to relieve the bottom of each cut (prevents splits from propagating at the base of each cut) by cross-drilling a 1/16" - 1/8" dia. hole that captures the end of the cut; then use a long ~<1/4" bit to drill the axis of the dowel down the length of the cross created by the 2 cross-cuts.  This last longitudinal hole will now accept a plastic screw anchor, the sharpened end of a pencil, another smaller dia. dowel rod, or any other rod-shaped wedge for spreading the 4 fingers to fit the inside of the head-tube. I'm not trying to co-opt your post, because it's a great solution.  It's just another approach in case the copper becomes deformed and/or brittle. --Bradley