Can I use #16 duplex wire extension to a 2800 watt chop-off cutter?
Definitely dependent on voltage and cord length. All modern UL listed portable motor-driven tools have wire gauge/length specs. included in the owner's manual. If you do not have the manual you should be able to do an internet search and get one. When in doubt, use heavier wire: a voltage drop across a cord that is too long and/or lightweight will damage the electric motor; bye-bye cut-off saw.