Civil Engineering Reference
In-Depth Information
Fig. 5.9. You should check the tramming of the milling machine's head before doing
an accurate piece of work and after doing any heavy metal removal.
X, Y, AND Z CO-ORDINATE SETTINGS
A milling machine's co-ordinate system is designated in three axes, each of
which can be sub-designated + or -. So, you can have X+ and X-, Y+ and Y-
and Z+ and Z-. The + part of the system is not normally used in practice be-
cause X+1 is the same as X1, but X-1 is not the same as X1, and similarly for
Y and Z.
Looking from the front of a milling machine, X- is the bit of table to the left
of the spindle; X+ is the bit of table to the right of the spindle. Y- is the bit of
the table nearest to you in front of the table, Y+ is the bit behind the spindle.
Z+ is above the bottom of the cutter and Z- is below the bottom of the cutter.
These are the six directions of movement of a milling machine.
Theseco-ordinatesareveryusefulwhenworkingwithadigitalreadout.You
can set the readout to the zero position that you require and then move in the
+ or - direction in any axis and get a direct readout of the position you are at.
If you do not have a readout on the Z axis, you could set the Z depth of the
cutter in various ways:
1) Wind up the table (if a knee machine) so the cutter just touches the work.
Then wind up the table by the amount the cutter needs to go into the work.
2) Place a spacer (possibly a drill shank) between the quill travel stop and
touch the cutter onto the top of the job. Remove the spacer, and the cutter is
set to the correct depth.
3) Set the Z by raising the table against a plunger dial test indicator moun-
ted on a magnet.
