Count full-form engagement at the actual interface
- External thread
The profile lies on the outside of the fitting. Confirm its full designation, coating condition and usable length.
- Internal thread
The thread lies inside the receiving hole or component. Its standard, fit and usable depth must match the external part.
- Thread engagementThis term
The arrow shows the overlapping region of the mating threads. Exclude unusable turns and account for the actual load and materials.
- Thread length
The overall threaded portion is a dimension of the fitting. It can exceed the full-form length available to the mating part.
- Thread runout
The profile becomes incomplete near the shoulder. Leave relief space and do not count this transition as full engagement.
- Thread tolerance class
The band represents permitted dimensional variation. Complete classes and coating conditions must be specified for each mating part.
The external part and internal part must overlap in usable thread turns. Total threaded length can include runout and incomplete turns; permitted fit also depends on tolerance class.
Conceptual sections. No minimum turn count, engagement length or tolerance class is specified by this figure.