After installing new blades I mowed for about an hour and then heard a loud grinding noise. I looked under the deck and saw that the right outside blade was loose. The bolt will not tighten...it just keeps turning. What to do?
you can replace that spindle Or remove it and put a helicoil replacement thread kit in it...
Or drill and tap it to a larger bolt... either of the first two choices will allow you to swap blades with no changes, the last will require changing the bolt hole size in the blade.
2009 Kubota RTV 900, 2009 Kubota B26 TLB & 2010 model LS P7010
Quickest, easiest is just replace the spindle that is if your dealer has it in stock. How old is your mower deck, likely that spindle has lots of wear on it and may fail shortly into the future anyway.