Isham Inc. recommends
that you do “chip removal” which may be done with a glove and
rubbing over the holes to make sure chips left from the drilling
process are removed. If you
are going to paint your airplane you may use a ScotchBrite pad
down the row of rivet holes to remove any burrs without removing
material that will result in an enlarged hole after
countersinking. If your
airplane will be polished aluminum you will not want to do this on
the outside surfaces.