After a few days soaking with penetrant, I punched, drilled, & extracted the 2 ex.man. bolts that had sheared. These
Irwin straight-flute extractors are good, but they only seem to work once. Next time, I'll buy the
square-body type, or
Rennsteigs. These Cobalt bits are a vast improvement over my old (ab-)used LH bits, but I still want to get new LH bits.