Chapter 10 Dimensioning
259
Symbols are also used to show whether the
hole is to be countersunk, spotfaced, or counter-
bored in manufacturing. See Figure 10-21. A
countersink is a chamfered recess at the end
of a smaller hole used to receive the head of a
fastener. A spotface is a recess at the end of a
smaller hole used to provide a bearing surface
for the head of a bolt or nut. A counterbore
is similar to a spotface, but the depth of the
recess is larger. See Figure 10-22.
When dimensioning a multiview drawing
of a cylinder, the diameter and length of the
cylinder should be dimensioned on the same
view (the secondary view), Figure 10-23A. In
other words, the diameter and length of the
cylinder should both be represented as linear
distances. If the diameters of several concentric
circles must be dimensioned on a drawing, it
may be more convenient to show them on the
longitudinal view, Figure 10-23B.
The correct way to use a leader to indicate a
diameter is shown in Figure 10-24. The leader
always points to the primary center of the
diameter. When the leader is placed “inside”
the circular feature, it intersects the primary
center of the diameter. Refer to Figure 10-19.
The tip of an arrowhead for any leader never
touches the primary center point, Figure 10-25.
these practices are common (the guidelines
shown are not ASME standards).
The dimensioning method shown in
Figure 10-19A is commonly used for diameters
of 1-1/2″ or greater. The method shown in
Figure 10-19B is commonly used for diameters
smaller than 3/4″. The method shown in
Figure 10-19C is commonly used for diameters
ranging from 3/4″ to 1-1/2″. The methods
shown in Figures 10-19D and 10-19E are for
use only when dimensioning sectional views.
Sectional views are discussed in Chapter 11.
Different conventions may be used for
dimensioning diameters depending on the
situation. For instance, if several concentric
circles are being dimensioned with diameters
greater than 1-1/2″ but increasing in size in
relatively small increments, the drafter may
choose not to use the common method for
large diameters (diameters 1-1/2″ and larger)
but rather one of the others to improve clarity.
The key is to select the convention that most
clearly does the job in any given situation.
Where it is not clear that a hole goes through
the part, the abbreviation THRU follows the
dimension. See Figure 10-20A. In cases where
the hole does not go through the entire part, the
depth of the hole is provided. See Figure 10-20B.
A special symbol is placed before the depth size.
1
_
2
3
_
8
B A
∅
Hole depth symbol
Goodheart-Willcox Publisher
Figure 10-20. Conventions for dimensioning holes. A—The abbreviation THRU is used with the hole size in views
where it is not clear that the hole goes through the part. B—The hole depth size is provided in cases where the
hole does not go through the entire part.
Copyright Goodheart-Willcox Co., Inc.
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Chapter 10 Dimensioning
259
Symbols are also used to show whether the
hole is to be countersunk, spotfaced, or counter-
bored in manufacturing. See Figure 10-21. A
countersink is a chamfered recess at the end
of a smaller hole used to receive the head of a
fastener. A spotface is a recess at the end of a
smaller hole used to provide a bearing surface
for the head of a bolt or nut. A counterbore
is similar to a spotface, but the depth of the
recess is larger. See Figure 10-22.
When dimensioning a multiview drawing
of a cylinder, the diameter and length of the
cylinder should be dimensioned on the same
view (the secondary view), Figure 10-23A. In
other words, the diameter and length of the
cylinder should both be represented as linear
distances. If the diameters of several concentric
circles must be dimensioned on a drawing, it
may be more convenient to show them on the
longitudinal view, Figure 10-23B.
The correct way to use a leader to indicate a
diameter is shown in Figure 10-24. The leader
always points to the primary center of the
diameter. When the leader is placed “inside”
the circular feature, it intersects the primary
center of the diameter. Refer to Figure 10-19.
The tip of an arrowhead for any leader never
touches the primary center point, Figure 10-25.
these practices are common (the guidelines
shown are not ASME standards).
The dimensioning method shown in
Figure 10-19A is commonly used for diameters
of 1-1/2″ or greater. The method shown in
Figure 10-19B is commonly used for diameters
smaller than 3/4″. The method shown in
Figure 10-19C is commonly used for diameters
ranging from 3/4″ to 1-1/2″. The methods
shown in Figures 10-19D and 10-19E are for
use only when dimensioning sectional views.
Sectional views are discussed in Chapter 11.
Different conventions may be used for
dimensioning diameters depending on the
situation. For instance, if several concentric
circles are being dimensioned with diameters
greater than 1-1/2″ but increasing in size in
relatively small increments, the drafter may
choose not to use the common method for
large diameters (diameters 1-1/2″ and larger)
but rather one of the others to improve clarity.
The key is to select the convention that most
clearly does the job in any given situation.
Where it is not clear that a hole goes through
the part, the abbreviation THRU follows the
dimension. See Figure 10-20A. In cases where
the hole does not go through the entire part, the
depth of the hole is provided. See Figure 10-20B.
A special symbol is placed before the depth size.
1
_
2
3
_
8
B A
∅
Hole depth symbol
Goodheart-Willcox Publisher
Figure 10-20. Conventions for dimensioning holes. A—The abbreviation THRU is used with the hole size in views
where it is not clear that the hole goes through the part. B—The hole depth size is provided in cases where the
hole does not go through the entire part.
Copyright Goodheart-Willcox Co., Inc.

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