Cut longer bar into pieces. How?

[nmasi]

You could just use a cold chisel to ensure you don't go too deep on the threads. Just give it a nice whack at a slight angle across the bottom. Enough to cut a notch in the bottom two or three threads. That way you don't have to worry about going too deep through the the T-nut ever again.

 

[Ebel440]

Sawzall work fine I use a harbor freight one. I cut .5 square steel in less then a minute with a burnt bent blade last week and it was as straight as a cheap bandsaw would do.