Should of course have used linisher, but an internet query returned substantially bigger machines.
Yes, one can flatten irons safely and easily. The bed can be angulated from flat to 90°; and the arm can be moved up, down, forward, and backward.
With the bed flat and the arm down, I placed a blade for a southpaw dovetail chisel across the belt resting against the arm, set the direction of the belt to run into the blade and arm, and – with the help of a small piece of wood glued to the blade (cyano acrylate) – applied a light pressure to the plane iron to be. A well used 120 grit belt did a good initial job, so I dared to move the arm along the belt, allowing for grinding its entire length, then changed to a fine grit belt for an improved surface, and was done.
Sadly, the steel – also after hardening – turned out to be too soft to hold an edge over any length of time.
London, UK; Boston, MA