Aligning a workpiece in a vice
There are the following cases to be considered:
a cube or similar
a round shape – horizontally
a round shape – vertically
In all of the cases it is assumed that:
The fixed jaw of the vice is vertical
the bottom of the vice is flat and
the fixed jaw is parallel to the table of the milling machine.
The alignment of the vice is covered:
The position of a cube is defined by:
the bottom of the vice,
the fixed jaw of the vice,
and the position of a stop on the left of the vice. This point can be defined by putting a cube in the vice. Setting the cube against this stop and then using a edge finder to determine the position of this relative to the spindle.
A round shape can be held horizontally in two ways. The axis of the round shape can be parallel to the jaws or it can be at right angles to the jaws.
If the axis is parallel to the jaws then the workpiece is being held by a line of contact with either jaw. This often proves to be unsatisfactory. It is usually better to place a V block od equivalent between the round shape and one of the jaws. Clearly the center of the round shape cannot be higher than the height of the jaws.
If the round shape is turned through 90° it has its two flat surfaces flat against each of the jaws. In this case the center height of the round part can be higher than the tops of the jaws.
If the round part is held so its axis is vertical then, again, a v-block of equivalent should be used between the part and one of the jaws.
The position of a round shape
A vertical round shape might be held using a V-block in the vice. Its bottom will be determined by the bottom of the vice. Usually it will be necessary to align its axis relative to that of the spindle. This can be done using the DTI on an arm device.