43°

APPENDIX

3  Q.  What  must  be  allowed  for  when  designing  a  fixture,  if
the  piece  has  previously  been  worked  upon  ?  A.  Allow  for
burrs.
4  Q.  Which  is  better  practice,  to  mill  toward  the  solid  or  the
movable  jaw  of  a  fixture?  A.  Toward  the  solid  jaw.
5  Q.  What  must  first  be  decided  before  a  jig  or  fixture  can  be
designed?  A.  The  locating  points  must  be  known.
6  Q.  What  relation  must  the  feet  of  a  jig  bear  to  the  guide
bushings  ?  A.  All  bushings  must  be  inside  the  geometrical
figure  formed  by  the  feet.
7  Q.  If  the  fixture  is  to  be  used  on  a  machine  which  has  “T”
slots,  what  should  be  provided  on  the  fixture?  A.  The
base  of  the  fixture  should  have  keys  or  tongues  to  fit  the
slots  and  they  should  be  square  with  the  holding  points.
8  Q.  Where  should  clamps  be  provided  to  best  resist  springing?
A.  Opposite  the  bearing  points.
9  Q.  Which  are  better  for  fixture  work,  straight  or  taper  pins?
A.  Taper  pins.
10  Q.  Which  would  be  the  better,  a  jig  designed  so  as  to  admit
the  piece  one  way  only,  or  one  into  which  the  piece  could
go  several  ways?  A.  Have  opening  so  as  to  allow  piece
correct  way  only.

47.  Apprentice  Test
(2)  Subtract  59763
47857

(1)  Add  8297

4335
1759

(3)  Divide  68256  4-432

(4)  Multiply  79643
X  448

(5)  Point  off  this  number  7607548.
(6)  Put  in  figures  in  decimal  form  this  number:—  Four  thousand, ­
  five  hundred  and  ninety-seven  hundred  thousandths.
(7)  The  answer  of  this  (427) 2  =