Long ago I started to seat new pushrods to new adjusters to insure a near perfect fit in the cups. I put the adjuster in a drill press and apply some valve grinding compound in the cup. Spin the drill and you can see the exact area of contact gain in size. what you want to see is a nice wide band of contact. The two stay as a pair after that.Why and what happens when this is done ? When you make some pulls or passes and go back for that final adjustment check there will be little or no change in lash that got larger that you normally would see .