Copyright Goodheart-Willcox Co., Inc.
Chapter 8 Creating and Working with Solid Model Features
205
Countersink
A countersink is like a counterbore with angled sides. The sides allow a fl at-head
machine screw or wood screw to sit fl ush with the surface of an object. A countersink
can be drawn in one of two ways. You can draw an inverted cone centered on a hole
and subtract it from the base or you can chamfer the top edge of a hole. Chamfering is
the quickest method.
1. Draw a cylinder representing the diameter of the hole, Figure 8-32A.
2. Subtract the cylinder from the base object.
3. Select the
CHAMFEREDGE
or
CHAMFER
command.
4. If using the
CHAMFEREDGE
command, pick the top edge of the hole and enter
the chamfer distance(s). Preview the result before completing the operation,
Figure 8-32B.
5. If using the
CHAMFER
command, select the top edge of the base object, enter the
chamfer distance(s), and pick the top edge of the hole.
Boss
A boss serves the same function as a spotface. However, it is an area raised above
the surface of an object. Draw a boss as follows.
1. Draw a cylinder representing the diameter of the hole. Extend it above the base
object higher than the boss is to be, Figure 8-33A.
2. Draw a second cylinder the diameter of the boss. Place the base of this cylinder
above the top surface of the base object a distance equal to the height of the boss.
Give the cylinder a negative height value so that it extends inside of the base object,
Figure 8-33B.
3. Union the base object and the second cylinder (boss). Subtract the hole from the
unioned object, Figure 8-33C.
4. Fillet the intersection of the boss with the base object, Figure 8-33D.
Subtract
A B
Figure 8-31.
Constructing a spotface.
A—The bottom of the
second, larger-diameter
cylinder should be
located at the exact
depth of the spotface.
However, the height
may extend above the
surface of the base.
Then, subtract the two
cylinders from the base.
B—The finished solid.
Edge to
chamfer
A B
Figure 8-32.
Constructing a
countersink. A—
Subtract the cylinder
from the base to
create the hole. B—
Chamfer the top of
the hole to create a
countersink.