Good timing for the question, just went through this today. Had two 6 x 1.00 mm screw heads bust off. They where in aluminum head on an air cooled VW. I went the usual route for me. Center punched the screws close to center, and drilled. I then grabbed a couple of easy outs. I've only had easy outs work maybe 1 in 10 times. This time I thought I put a little heat on them with a MAPP gas torch to see the effect. The effect was to my chagrin it softened the easy out metal. Anyway the usual end results was drill and tap. I've had thoughts there is a design flaw in easy outs. Your trying to remove a thread that is already to tight to unscrew, rust corrosion, galled threads, whatever. So you drill a hole for the easy out, and then tap a tapered rod into the hole. Isn't a the reverse threads and taper going to force its way further in the hole putting more pressure outwards on the threads. The easy outs that are square, tapered, and have the cutting edge seem to be designed to get around wedging. Unfortunately I've found that for the edges to grab you have to force them harder into the hole, same results wedging. That and since the easy outs are tapered you are putting most of the pressure at or near the entry to the hole. There must be a trick to getting these things to work.
I haven't used a left hand drill yet. I did pick up some cheap "easy outs" that were left handed drill tips. They looked like they were designed to dig in as it was turned, did work. A left handed drill would work better at least it would create some heat as it drilled through.
Larry
