class - Proper design of Java Classes -

my question should make counterbore (a recessed hole in plate) property of plate or should counterbore property of joint

i have following classes engineering analysis program:

plate bolt washer nut  material coating 

i have classes represent various joints

tappedjoint (a joint bolt threaded bottom plate) have:   plate topplate   plate bottomplate   bolt bolt   washer topwasher  boltedjoint   plate topplate   plate bottomplate   bolt bolt   nut nut   washer topwasher   washer bottomwasher 

the counterbore applicable on topplate need validation user enters plate thickness greater depth of counterbore. set counterbore null in bottomplate or better put counterbore property in joint class? or perhaps should using other pattern such subclasses?

coating , material add property each part because verbose add joint i.e.:

  boltedjoint     plate topplate     plate bottomplate         coating topplatetopsurface     coating topplatebottomsurface     coating bottomplatetopsurface ...etc  

i can work either scenario perhaps better design?

i think if make counterbore property of joint both plate , bolt can access property specific each joint. way, bolt need not access plate object finding holes.