hi i have a 2005 lazer xs 31hp briggs 72" deck purchased in october 05. back in 5/2/07 i had to replace the center spindle due to the last 1/2" if the blade bolt threads stripping off. i contributed that to impact use even though i hand snug them. on 8/19/07 i had to replace it due to the same problem, except since last replacement i have only used hand tools to install and remove them. it seems to be stripping on the way out, as i hand tighten them and snug them with a hand wrench. this unit only has 340 hours on it. do you have any ideas as to what may be causing this? i have replaced them out of pocket even though it is under warranty because i cannot afford the down time to have the dealer fix it. i did show them the parts and they said they had never seen anything like it.