I consulted a engineer and he did all my calculations and recommended 2 1 1/2 x 9 lvl for my new girder. I would like to use them as a flush mount with joist hangers. I have temporarily supported the joist with a wall and marked all my joist. My question is what will be the best way to get a clean cut on the 2x6 joist.
Careful work with a reciprocating saw is a pretty good way to do this. Although it would be ideal to be perfectly tight, if you're within 1/8" to 1/4" you'll have adequate bearing in your joist hangers. Just use a square to draw a straight vertical line to follow with the saw.