Unit 11 Machining Specifications and Drawing Notes 205
Chamfered Edges
Beveled edges on parts are common for a
variety of reasons and are often called chamfers. One
reason for chamfering an edge is to remove burrs.
In essence, a chamfered edge around a hole is the same
as a countersink, but the term countersink is more
commonly used with smaller holes. A countersink
bit can perform the operation on smaller holes.
The term chamfer is more often applied for larger
holes. It also describes a straight edge that has been
beveled. The end of a cylinder is also chamfered in
many cases to allow for easier assembly.
Figure 11-11 illustrates different methods for
specifying a chamfer on the print, either by using a
local note or by using linear and angular dimensions.
If a chamfer is 45fl, the leg distance is the same on
both sides. For angles other than 45fl, a leg distance
must be specified. Figure 11-12 shows recommended
standard practice for chamfered edges where surfaces
are not 90fl to each other.
Necks and Undercuts
Sometimes a groove or neck is cut into a
cylindrical surface for a retaining ring or to
provide a good transition between two features.
The groove is dimensioned by a local note, such as
.06 WIDE X .03
DEEP. Linear measurements that
specify the resulting diameter within the groove
.750 THRU
1.000
82°
.750
.125 X 45° CHAMFER
BOTH ENDS
Example 1 Example 2
Figure 11-9.
Countersunk holes are holes with a cone-shaped enlargement and can be dimensioned by note. Chamfer depth can
also be dimensioned as shown on the right in example 2.
Figure 11-10.
A counterdrilled hole has a conical transition that
does not require an angular dimension. The depth
measurements are for the full-diameter distances.
Example 1 Example 2
Figure 11-11.
Chamfers on the end of a cylinder can be dimensioned
by note (example 1) or by dimensions (example 2).