DTI stands for direct tension indicator, a load-indicating washer used on structural bolts. Small protrusions on one face crush as the bolt is tightened, and the installer or inspector checks the remaining gaps with a feeler gauge, typically 0.005 in, counting how many gaps refuse it. Because it reads tension at the joint, it is unaffected by thread or nut-face friction.
Inspector's going around with the five-thou feeler on every DTI, so don't stop short on any of them.
Also heard as
- direct tension indicator
- load-indicating washer
Related terms
Squirter
Shop name for a direct tension indicator filled with colored silicone that squirts out when the bolt is tight.
A325
The workhorse high-strength structural bolt: heavy hex, quenched and tempered, 120 ksi minimum tensile.
Turn-of-nut
A pretensioning method that snugs the nut, match-marks it, then turns it a fixed fraction of a turn.
TC bolt
Tension control bolt: a structural bolt with a splined tip that shears off once the right tension is reached.