ok, so its at my parents place, storm blew down half the crown out of a london plane. Approx 10" trunk at 1 foot above ground. Failed at an area where 4 branches originated not an included union. seems it twisted at the failure point. This is not my normal business practice, I am mainly landscaping yards (installs and some maintenance) and pruning from the ground only. I got to use my Dad's POS 12" bar ELECTRIC chainsaw so he would shut up. I made the face cut with it and used my silky the rest of the cuts, it cut 3 times as fast. Piled the bits and waved as I left for home. oh, failure point was about 6 inch diameter.