27  If  the  pattern  is  mounted  in  a  frame,  the  depth  of  the  drag  half
of  the  flask  must  be  further  corrected  by  deducting  an  amount  equal
to  the  thickness  of  the  frame.  The  frame  should  always  be  considered
as  belonging  to  the  drag  half  of  the  flask.
28  Table  1  gives  the  minimum  depth  of  flask  which  experience
has  shown  to  be  permissible  for  a  cope,  squeezed  by  power,  in
order  that  the  sand  may  support  its  own  weight.
29  If  the  conditions  require  a  deep  flask,  or  one  which  is  larger
than  either  of  the  two  sizes  mentioned,  care  should  be  taken  when-
ever possible  to  avoid  molds  beyond  the  capacity  of  a  single  operator.
968


PATTERNS   FOR   REPETITION   WORK


30    For  snap  flask  work  the  limits  for  a  one-man  mold  are  about
as  follows:

A  Width  12  inches  inside  of  flask.     A  greater  width  makes  the

mold  liable  to  tip  toward  or  from  the  operator.
B  Length  24  inches  inside  of  flask.     A  greater  length  requires

an  excessive  spread  of  the  arms.
C  Weight  85  pounds  corresponding  roughly,  for  flasks  of

average  depth,  to  an  internal  flask  area  of  250  square

inches.
PLATS


PATTERN


FIG.  2    "PLATE"  PATTERN

31  Care  should  be  exercised  to  avoid  molds  which  are  square  or
nearly  square,  as  they  are  liable  to  tip,  even  if  the  width  is  less  than
the  12  inches  specified  above.  The  best  shape  is  obtained  when  the
width  is  from  ^^  to  ^  of  the  length.
