Refers to the arc characteristics that you normally see with a 6010 electrode. A ?digging? arc is one in which you can see parent metal being penetrated at the arc.
Digging | Definition of Digging at Dictionary.com
Digging by Seamus Heaney | Poetry Foundation
San Jose, CA – Official Website – Underground Service Alert (USA)
Digging – definition of digging
Digging – Idioms