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This specification covers the requirements for carbon and alloy steel compressible-washer-type direct tension indicators (DTIs) capable of indicating a specified bolt tension in cap screws, bolts, anchors, and studs. These DTIs are intended for installation under a bolt or cap screw head, a hex nut, or against a hardened washer or other flat hardened surface. The following are two types of DTIs: Type 1 DTIs are suitable for comparatively large bearing surfaces and Type 2 DTIs are suitable for comparatively smaller bearing surfaces. DTIs shall have a configuration produced by extrusion, punching, pressing, or similar forming to permit a measurable decrease in thickness when placed in compression. The design shall be such that the degree of plastic deformation of the protrusions shall indicate the tension in a tightened cap screw, bolt, anchor, or stud. The process used for heat treatment of DTIs, if required, shall be through-hardening by heating to a temperature above the upper transformation temperature, quenching in oil, and then tempering by reheating to a suitable temperature to attain desired mechanical/performance properties. Protective coatings, platings, or finishes may be applied on the DTIs if specified. Compression load and hardness of the DTIs shall be determined by performing mechanical tests.

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1.1 This specification covers the requirements for carbon and alloy steel compressible-washer-type direct tension indicators capable of indicating a specified bolt tension in cap screws, bolts, anchors, and studs.

1.2 Direct tension indicators in nominal diameter sizes ¹/₄ through 2¹/₂ in. are covered.

1.3 There are two Types of DTIs covered by this specification, Type 1 and Type 2.

1.3.1 Type 1 DTIs are suitable for comparatively large bearing surfaces. Type 1 DTIs are available in Grades 55 and 105, which differ in the amount of tension they indicate at a prescribed gap (see Table 1).

Note 1—Examples of a comparatively large bearing surface would include heavy hex bolts, heavy hex nuts, and so forth.TABLE 1 Acceptable Range of Compression Load^A

DTI
Nominal
Diameter
(in.)

Mean Compression Load^B Range
in Pounds (lbs)

Mean Compression Load^C Range
in Pounds (lbs)

Grade 5

Grade 8

Grade 55

Grade 105

¹/₄ 

2200 to 2450

3100 to 3450

. . .

. . .

⁵/₁₆ 

3500 to 3850

4950 to 5500

. . .

. . .

³/₈ 

5300 to 5850

7500 to 8300

. . .

. . .

⁷/₁₆ 

7200 to 7900

10 100 to 11 200

. . .

. . .

¹/₂ 

9700 to 10 700

13 700 to 15 340

4450 to 4900

8500 to 9400

⁹/₁₆ 

12 350 to 13 600

17 400 to 19 200

5700 to 6300

10 900 to 12 050

⁵/₈ 

15 550 to 17 200

21 850 to 24 200

7050 to 7800

13 500 to 15 000

³/₄ 

22 600 to 25 000

31 900 to 35 300

10 500 to 11 600

20 000 to 22 150

⁷/₈ 

30 850 to 34 100

43 550 to 48 100

14 500 to 16 000

27 650 to 30 550

1

40 200 to 44 400

56 700 to 62 700

19 000 to 21 000

36 250 to 40 100

1¹/₈ 

40 250 to 44 450

73 150 to 80 900

23 950 to 26 450

47 300 to 52 300

1¹/₄ 

51 100 to 56 450

91 750 to 101 450

30 400 to 33 600

59 850 to 66 150

1³/₈ 

61 150 to 67 600

112 450 to 124 250

38 550 to 42 600

73 800 to 81 600

1¹/₂ 

74 350 to 82 150

135 150 to 149 400

44 050 to 48 700

89 300 to 98 700

1⁵/₈ 

. . .

. . .

55 800 to 61 700

106 200 to 117 400

1³/₄ 

74 450 to 82 300

177 850 to 196 500

59 550 to 65 850

124 600 to 137 750

1⁷/₈ 

...

206 050 to 227 750

75 550 to 83 500

144 500 to 159 700

2

98 000 to 108 300

236 850 to 261 750

78 650 to 86 950

165 800 to 183 300

2¹/₄ 

127 400 to 140 800

277 900 to 307 100

102 050 to 112 750

212 900 to 235 350

2¹/₂ 

156 750 to 173 250

379 600 to 419 600

125 400 to 138 600

240 550 to 265 850

^A Compression load requirements establish the capability of the direct tension indicators to satisfy typical tension requirements for these grades. The user is not obliged to install fasteners and DTIs to these tensions, and is free to specify installation to lower tension values. When so specified, the DTI supplier shall provide a load-gap curve in accordance with 15.2 to enable the user to select the appropriate gap criteria for the intended target tension of the application.^B The Mean compression load values for Grades 5 and 8 in nominal sizes up through 1-¹/₂ in are based upon 75% of the proof load for SAE J429 cap screws. For Grade 5 in nominal sizes over 1-¹/₂ in and up to 2-¹/₂ in inclusive, the mean compression load values are based on 75% of the proof load for ASTM A449. For grade 8 in nominal sizes over 1-¹/₂ in and up to 2-¹/₂ in inclusive, mean compression load values are based upon 75 % of the proof load for ASTM A354BD.^C Mean compression load values for Grades 55 and 105 are based upon 60 % of the yield strength for the matching fasteners on which they are used.

1.3.2 Type 2 DTIs are suitable for comparatively smaller bearing surfaces.Type 2 DTIs are available in Grades 5 and 8, which differ in the amount of tension they indicate at a prescribed gap (see Table 1).

Note 2—Examples of a comparatively small bearing surface would include a hex cap screw, hex nut, and so forth.

1.4 Direct tension indicators are intended for installation under a bolt or cap screw head, a hex nut, or against a hardened washer or other flat hardened surface.

1.5 The values stated in inch-pound units are to be regarded as standard. No other units of measurement are included in this standard.

1.6 The following precautionary statement pertains only to the test method portions, Section 12 and Appendix XI of this specification: This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.