Sep 2025
ASTM F959
ASTM F959 – Direct Tension Indicator Washers
ASTM F959 specifies the requirements for compressible washer-type direct tension indicators (DTIs) designed for structural bolting applications. These washers, available in sizes from 1/2” to 1-1/2”, provide a reliable method of verifying that the required minimum bolt tension has been achieved.
DTI washers are manufactured in two grades, suitable for use with both ASTM A325 and ASTM A490 structural bolts, and are also offered in a weathering steel option to ensure durability in outdoor or corrosive environments. By using ASTM F959 washers, installers can achieve proper bolt preload and enhance the safety and performance of steel connections.
ASTM F959 Direct Tension Indicator Washer Types and Applications:
| Type 325 / 325-3 |
Designed for use with ASTM A325, F1852, A325-3, and F1852-3 structural bolts |
| Type 490 / 490-3 |
Compatible with ASTM A490, F2280, A490-3, and F2280-3 structural bolts |
Bolt Tension Ranges – ASTM F3125 Type 325 & Type 490 Bolts:
| Bolt Diameter (inches) |
Type 325 / 325-3 – Tension Range (kips) |
Type 490 / 490-3 – Tension Range (kips) |
| 1/2" |
12 – 14 |
15 – 18 |
| 5/8" |
19 – 23 |
24 – 29 |
| 3/4" |
28 – 34 |
35 – 42 |
| 7/8" |
39 – 47 |
49 – 59 |
| 1" |
51 – 61 |
64 – 77 |
| 1-1/8" | 64-77 | 80-96 |
| 1-1/4" |
81-98 | 102-122 |
| 1-3/8" |
97-117 | 121-145 |
| 1-1/2" |
118-143
| 148-178 |
Chemical Composition Limits – High Strength Bolts (Type 325 / 490 & Type 325-3 / 490-3) :
| Element |
Type 325 & 490 |
Type 325-3 & 490-3 |
| Carbon |
0.30 – 0.55% |
— |
| Manganese |
0.50 – 0.90% |
— |
| Phosphorus (max) |
0.040% |
0.040% |
| Sulfur (max) |
0.045% | 0.050% |
| Silicon |
0.15%-0.35% | 0.15%-0.35% |
| Chromium |
— | 0.45-0.65% |
| Nickel |
— | 0.25-0.45% |
| Copper |
— | 0.25-0.45% |