Composite position uses two stacked segments in one feature control frame. The upper segment controls the pattern’s overall location and orientation to the full datum reference frame. The lower segment refines the relationship among features within that pattern.
The upper segment: place the pattern
The top segment establishes the broader position requirement for the pattern relative to the primary, secondary, and tertiary datums. It controls where the pattern belongs in the part or assembly.
The lower segment: refine the pattern
The lower segment provides a tighter requirement for the feature-to-feature relationship inside the pattern. Its repeated datum references establish which orientation relationships remain constrained while the pattern is refined.
Why it is useful
A bolt pattern may need to be accurately located to a housing while also requiring much tighter spacing among its holes. Composite position expresses both functional needs without forcing the tighter internal pattern relationship to control every aspect of location.
Example: a four-hole pattern
The upper segment locates the pattern from A-B-C. The lower segment tightens the relationship inside the pattern while retaining the datum references shown in that segment.
Common mix-up
Composite position is not simply two separate position frames stacked together. The two segments work as one composite requirement and must be interpreted as a pair.
Keep learning
Explore the foundations
Foundation 01
Datums
Open guide →Foundation 02
Feature Control Frames
Open guide →Foundation 03
Maximum Material Condition (MMC)
Open guide →Foundation 04
Least Material Condition (LMC)
Open guide →Foundation 05
Basic Dimensions & Tolerance Zones
Open guide →Foundation 06
Regardless of Feature Size (RFS)
Open guide →Foundation 07
Rule #1 & Features of Size
Open guide →Foundation 08
Virtual Condition & Functional Gaging
Open guide →Foundation 09
Datum Feature Modifiers & Datum Shift
Open guide →Foundation 10
Composite PositionCurrent page