Chain Bar "Dressing" tool. Is this necessary and used by professionals?

[doobin]

Milwaukee powerfile with an 80 grit ceramic belt. 
 

 

[doobin]

18 hours ago, Muddy42 said:

I've never used one.  I generally clean the bar first in soapy water.  Then I use a flat file to take off any burs, then I have a good look for squareness with a mini set square and flatness with a piece of aluminium. I also use a magnetic spirit level on the bar, knowing my vice and workbench are perfectly level. I bang dings with a hammer. Finally once flat, I remove the tracks in the rails where the teeth run.

With respect, a little torpedo level on the bar on the bench won’t tell you shit. It’ll make you feel good but that’s about it. 
 

Steel straight edge is what you need. A peice of aluminium is liable to be bent from the off unless it’s an extruded profile. 

[Brushcutter]

A bench belt sander is also really good for dressing bars. At least short ones.