DX520500
FASTENERS
Delphi Interior Systems
Originating Site: Fasteners Specialist Team
Approved Supplier List (Y/N): N
MECHANICAL AND MATERIAL REQUIREMENTS FOR METRIC
EXTERNALLY THREADED FASTENERS
DX520500
1. SCOPE
1.1 This standard covers the mechanical and material requirements for six property classes of carbon and alloy steel externally threaded metric fasteners in nominal thread diameters M1.6 to M36, inclusive, suitable for use in general engineering applications. Products included are bolts, screws, studs, U-bolts and sems and hardness of HRC39 max. Tapping screws, thread rolling screws, self drilling tapping screws and set-screws are NOT included.
1.1.1 The term "stud" as referred to herein applies to a cylindrical rod of moderate length, threaded on either one or both ends or throughout its entire length. It does not apply to headed, collared or similar products which are more closely characterized by requirements shown herein for bolts.
1.1.2 For specification purposes, this standard treats U-bolts as studs. Thus, wherever, the word "studs " appears, "U-bolts" is also implied. U-bolts covered by this standard are those used primarily in the suspension and related areas of vehicles. (Designers should recognize that the "U" configuration may not sustain a load equivalent to two bolts or studs of the same size and grade; thus actual load carrying capacity of U-bolts should be determined by saddle load tests.)
1.2 Requirements for the 6 property classes, DX520501 – DX520506, are essentially identical with requirements given for these classes in ISO 898/I and ASTM F568.
1.3 The product size range for which each property class is applicable is given in Table 1.
1.4 DESIGNATION
1.4.1 The specification number shown in the title is a generic number for six property classes of metric externally threaded fasteners.
1.4.1.1 Drawing Call Out
Drawing call out example: DX520505 (Metric Externally Threaded Fastener – Property Class 9.8)
PROPERTY CLASS CONVERSION TABLE
Delphi Property Class
(Metric) ASTM/SAE Property Class
(Metric)
ASTM
(Inch)
SAE Grade
(Inch)
DX520501 4.6 A307A 1
DX520502 4.8 --- ---
DX520503 5.8 --- 2
DX520504 8.8 A449 5
DX520505 9.8 A449 5
DX520506 10.9 A354BD 8
1.4.2 ASTM/SAE Property Class Designation System
1.4.
2.1 Property classes are designated by numbers where increasing numbers represent increasing tensile strengths. The designation symbol consists of two parts.
1.4.
2.2 The one or two numerals preceding the first decimal point approximates 1/100 of the minimum tensile strength in MPa.
1.4.
2.3 The numeral following the decimal point approximates 1/10 of the ratio, expressed as a percentage, between minimum yield stress and minimum tensile strength.
2. REFERENCED STANDARDS
ASTM E18 ASTM F568 DX000005DX520007
DX520009ISO 898/I ISO 965 SAE J417
3. ENVIRONMENTAL/SAFETY REQUIREMENTS
All materials supplied to this specification must comply with the requirements listed in DX000005.
4. MATERIAL PROPERTIES
4.1 MATERIAL
4.1.1 Steel
Bolts, screws and studs shall be made of steel conforming to the description and chemical composition requirements specified in Table 1 for the applicable property class.
TABLE 1 – CHEMICAL COMPOSITION REQUIREMENTS
Product Analysis, % Property Carbon Phosphorus Sulfur DX No. Class Material and Treatment Min Max Max Max
DX520501 4.6 Low or medium carbon steel --- 0.55 0.048 0.058
DX520502 4.8 Low or medium carbon steel
--- 0.55 0.048 0.058 (product partially or fully annealed as required)
DX520503 5.8 Low or medium carbon steel, cold worked 0.13 0.55 0.048 0.058
0.28 0.55 0.048 0.058
DX520504 8.8 Medium carbon steel
(product quenched and tempered) (NOTE 1)
DX520505 9.8 Medium carbon or medium carbon alloy steel
0.28 0.55 0.048 0.058
(product quenched and tempered)
(NOTES 1, 2 and 3)
0.28 0.55 0.040 0.045
DX520506 10.9 Medium carbon alloy steel
(product quenched and tempered) (NOTE 3)
1 The manufacturer may use for sizes thru M16 a low carbon martensite steel with 0.15-0.27%, 0.74 - 1.46%, carbon manganese, 0.038% max phosphorus, 0.048% sulfur, and 0.0005 - 0.003% boron.
2 For DX520505 screw and washer assemblies (sems), size 1.6 thru 12, carbon content may be 0.15 - 0.55%.
3 Medium carbon alloy steel shall be fine grain, with hardenability that will produce a minimum hardness of HRC47 at the center of the threaded section one diameter from the end of the bolt, screw or stud after oil quenching. SAE 1541 (AISI 1041) steel may be used, oil quenched and tempered, at option of the producer for products M12 in diameter and smaller. Use of alloy steel with Boron to increase hardenability for sizes larger than M12 is permissible.
4.2 HEADING
Methods other than upsetting and/or extrusion are permitted only by special agreement between purchaser and producer.
4.2.1 DX520501 may be hot or cold headed at the option of the manufacturer.
4.2.2 DX520502 – DX520506 bolts and screws in nominal thread diameters up to M20 inclusive, with lengths up to 10 times the nominal product size or 150 mm inclusive shall be cold headed. Grain flow must follow contour of fillet. No end grain exposure is allowed. Larger diameters and longer lengths may be cold or hot headed at the option of the manufacturer.
4.3 THREADING
DX520502 – DX520506 bolts and screws in sizes up to M20 inclusive, and in product lengths up to 150 mm inclusive, shall be roll threaded, except by special agreement. Threading practice for other sizes of bolts and screws and all sizes of studs shall be at the option of the manufacturer.
4.4 HEAT TREATMENT
DX520501 bolts and screws and DX520501-DX520503 studs need not be heat treated.
4.4.1 DX520502 – DX520503 bolts and screws shall be stress relieved to assure the soundness of the head to shank junction. The stress relief temperature for class DX520503 bolts and screws shall be 470°C minimum.
4.4.2 DX520504-DX520505 bolts, screws and studs shall be austenitized, oil or water quenched to obtain a structure of 90% martensite minimum and tempered at a minimum temperature of 425°C for class DX520504 and 410°C for class DX52050
5.
NOTE: For class DX520505 screw and washer assemblies (sems) quenchants whose principal constituent is water shall NOT be used, and tempering temperature shall be no less than 340°C.
4.4.3 Medium carbon alloy steel DX520506 bolts, screws and studs shall be austenitized, oil quenched to obtain a structure of 90% martensite minimum and tempered at a minimum temperature of 425°C.
4.4.4 Tempering - Temperature - Audit Test
This test is a means for checking whether products were tempered at the specified temperature. The hardness (mean hardness of three hardness readings) of a bolt, screw, or stud as manufactured shall be measured. The product shall be retempered for a minimum of 30 min. per 25 mm of nominal diameter, but not less than 30 min., at a temperature 10°C less than the minimum tempering temperature specified for the property class and material (See 4.4.4.1 The hardness of the retempered product shall then be measured. The difference between the hardness of the product before and after retempering shall not exceed 2 points HRC for DX520506 and 3 points HRC for DX520504 and DX520505.
4.5 DECARBURIZATION
Unless otherwise specified, classes DX520504 – DX520506 shall conform to the decarburization limits specified in Table 5 when tested in accordance with DX520009.
TABLE 2 – DECARBURIZATION LIMITS FOR THREADS
5. REQUIREMENTS
TABLE 3 – MECHANICAL REQUIREMENTS FOR BOLTS, SCREWS AND STUDS
1 Yield strength is stress at which a permanent set of 0.2% of gage length occurs.
2 Surface hardness shall not exceed base metal hardness by more than 2 points (HRC equivalent) and in
the case of DX520506 shall not exceed HR15N80. (HRC39 Equivalent). Surface hardness measured at HV
0.3 shall not exceed core hardness readings (HV 0.3) by more than 30 vicker points. For DX520506, the
surface hardness must not exceed HV390.
3 For class DX520505 screw and washer assemblies (sems), base metal hardness may be HRC25-39 and
surface hardness shall not exceed Rockwell 15N80.
5.1 MECHANICAL PROPERTIES
Bolts, screws and studs shall meet the mechanical requirements specified for that product in Table 3. Products indicated in Table 4 must be wedge tensile tested; all others shall be axial tensile tested. However, those head bolts and screws with special configurations, such as drilled heads, which make the heads weaker than the threaded section, and short bolts/screws (length smaller than 3 diameter) shall be excluded from tensile testing unless otherwise specified on part drawing.
5.2 TEST METHODS
5.2.1 Product Hardness (Base Metal)
For routine inspection, hardness of bolts, screws and studs may be determined on head end or shank, after removal of any plating or other coating to assure an accurate base metal hardness. For cold formed, non heat treated products, hardness shall be determined on the threaded end. For referee purposes, the hardness of bolts, screws and studs shall be determined at mid-radius of a transverse section through the threaded portion taken at a distance of one diameter from the end of the product. The reported hardness shall be the average of four hardness readings located at 90° to one another. The preparation of test specimens and the performance of hardness tests shall be in conformity with the requirements of SAE J417 and/or ASTM E18.
5.2.2 Surface Hardness
Tests to determine surface hardness shall be conducted on the ends, hexagon flats or unthreaded shanks of bolts, screws and studs which have been prepared per 5.1 above to insure accurate reproducible readings in accordance with SAE J417. Proper correction factors shall be used when hardness tests are made on curved surfaces, per ASTM E18.
5.2.3 Proof Load
The proof load test consists of stressing the bolt, screw or stud with a specified load which the product must withstand without permanent set.
5.2.3.1 The overall length of the specimen shall be measured between conical or ball centers on the specimen, using mating centers on the measuring anvils. The specimen shall be marked so that it can be placed in the measuring fixture in the same position for all measurements. The measurement instrument shall be capable of measurement to 2.5 μm. The grips of the testing machine shall be self-aligning to avoid side thrust on the specimen. For bolts and screws, the specimens shall be assembled in the fixture of the tensile machine so that 6 complete threads are exposed between the grips. This is obtained by freely running the nut or fixture to the thread runout of the specimen and then unscrewing the specimen 6 full turns. When proof load testing studs, one end of the stud shall be assembled in a threaded fixture to the thread runout. For studs having unlike threads, this shall be the end of the finer pitch thread. For studs having unlike diameters (step studs), this shall be the end with the smaller minor diameter. The other end of the stud shall likewise be assembled in a threaded fixture, except it shall be unscrewed 6 full turns from the thread runout, thus leaving 6 complete threads exposed between the grips. The bolt, screw or stud shall then be axially loaded to the proof load specified for the applicable size, thread series, and class in Table 5, the load retained for a period of 15 s, the load removed, and the overall length again measured. The speed of testing, as determined with a free running cross head, shall not exceed 3 mm/minute.
NOTE: In the case of sems, washers may be removed prior to testing; however, for referee testing washers shall be removed.
5.2.3.2 To meet the requirements of 5.1, the length of the bolt, screw or stud after loading shall be the same as before loading within a tolerance of 12.5 μm allowed for measurement error.
5.2.3.3 Variables, such as straightness and thread alignment (plus measurement error), may result in apparent elongation of the fasteners when the proof load is initially applied. In such cases, the fastener may be retested using a 3% greater load, and may be considered satisfactory if the length after loading is the same as before this loading (within the 12.5 μm tolerance for measurement error).
5.2.4 Axial Tensile Strength
Bolts, screws or studs shall be assembled in the testing machine with 6 complete threads exposed between the grips and axial loading applied until failure. The grips of the testing machine shall be self-aligning to avoid side thrust on the specimen. Typical fixturing is illustrated in Figure 1. The speed of testing, as determined with a free running cross head, shall not exceed 25 mm/minute.
FIGURE 1 – TENSILE TESTING OF FULL SIZE BOLT OR SCREW
5.2.4.1 To meet the requirements of 5.1, the bolt, screw or stud shall support a load not less than the minimum tensile strength specified for the applicable size, thread series, and class in Table 5 prior to product fracture. In addition, for bolts and screws, (except flat and oval head machine screws) the fracture shall occur in the body or threaded section with no failure at the junction of the head and shank.
5.2.5 Wedge Tensile Strength
5.2.5.1 Bolts or screws shall be assembled with a wedge inserted under the head, as illustrated in Figure 2, installed in the testing machine and tensile tested to failure, as described in 5.2.4. The angle of the wedge for the bolt or screw size and class is specified in Table 4. The wedge shall be so placed that no corner of a square or hexagon head takes the bearing load; that is, a flat of the head shall be aligned with the direction of uniform thickness of the wedge. The wedge shall have a minimum hardness of HRC45. The wedge shall have a thickness of one-half the bolt or screw diameter measured at the thin side of the hole. The hole in the wedge shall have the following clearance over the nominal size of the bolt or screw, and its top and bottom edges shall be rounded or chamfered 45° to the following dimensions:
Nominal Bolt
Or Screw Size (mm)
Clearance in Hole Approximate
(mm)
Radius or Depth of Chamfer
Approximate
(mm) 1.6 – 3 0.5 0.5 4 – 5 0.7 0.7 6.0 – 10 0.8 0.8 12 – 16 1.0 1.6 20 – 30 1.3 2.4 36
1.5
3.0
TABLE 4 – TENSILE TEST WEDGE ANGLES
Product
DX No. Property Class Nominal Diameter (mm)
Wedge Angle
(deg)
Hex and hex washer head machine screws and sems DX520502 DX520505 4.8 9.8 Thru M12
6 Hex bolts and screws threaded one diameter and closer to underside of head
DX520504 DX520505 DX520506 8.8 9.8 10.9 Thru M20
Over M20 to M36
6 4 Hex flange and hex washer head bolts and screws
DX520501 DX520502 DX520503 DX520504 DX520505 DX520506 4.6 4.8 5.8 8.8 9.8 10.9 Thru M36
6
All other hex bolts and screws
DX520501 DX520502 DX520503 DX520504 DX520505 DX520506
4.6 4.8
5.8 8.8 9.8 10.9 Thru M24
Over M24 to M36
10 6 Studs
All
All
Thru M20
Over M20 to M36 6 4
FIGURE 2 – WEDGE TEST DETAILS – BOLTS AND SCREWS
C = Clearance of hole
D = Diameter of bolt or screw R = Radius or chamfer
T = Thickness of wedge at thin side of hole equals one half diameter of bolt or screw W = Wedge angle (See Table 4)
5.2.5.1.1 To meet the requirements of 5.1, the bolt or screw shall support a load not less than the minimum tensile strength specified for the applicable size, thread series and class in Table 5 prior to product fracture. In addition, the fracture shall occur in the body or threaded section with no failure at the junction of head and shank. 5.2.5.2 Studs
Following proof load testing, one of the same studs shall be assembled in a threaded fixture to the thread runout. For studs having unlike threads, this shall be the end with the finer pitch thread. For studs having unlike diameters (step studs), this shall be the end with the smaller minor diameter. The other end of the stud shall be assembled in a threaded wedge to the runout and then unscrewed 6 full turns, thus leaving 6 complete threads exposed between the grips, as illustrated in Figure 3. The angle of the wedge for the stud size and class shall be as specified in Table 3. The stud shall be assembled in the testing machine and tensile tested to failure, as described in 5.2.3.
The wedge may be either circular or square. The recommended outside dimension of the wedge is 45 mm for bolt and screw sizes through 20 mm, and 90 mm for bolt and screw sizes 24 through 36 mm.
TABLE 5 – PROOF LOAD AND TENSILE STRENGTH VALUES (1)
DX520501 DX520502 DX520503 DX520504 DX520505 DX520506 Nominal Thread Dia. & Thread Pitch Stress Area (Note 2) (mm 2) Proof Load (kN) Tensile Strength Minimum
(kN) Proof Load (kN) Tensile Strength Minimum
(kN) Proof Load (kN) Tensile Strength Minimum
(kN) Proof Load (kN) Tensile Strength Minimum
(kN) Proof Load (kN) Tensile Strength Minimum
(kN) Proof Load (kN) Tensile Strength Minimum
(kN) M1.6x0.35 1.27 0.39 0.53 0.83 1.14 M2x0.4 2.07 0.64 0.87 1.35 1.86 M2.5x0.45 3.39 1.05 1.42 2.20 3.05 M3x0.5 5.03 1.56 2.11 3.27 4.53 M3.5x0.6 6.78 2.10 2.85 4.41 6.10 M4x0.7 8.78 2.72 3.69 5.71 7.90 M5x0.8 14.2 3.19 5.67 4.40 5.96 5.4 7.38 9.23 12.8 11.8 14.8 M6x1 20.1 4.52 8.04 6.23 8.44 7.64 10.5 13.1 18.1 16.7 20.9 M8x1.25 36.6 8.24 14.6 11.3 15.4 13.9 19.0 23.8 32.9 30.4 38.1 M10x1.5 58.0 13.1 23.2 18.0 24.4 22.0 30.2 37.7 52.2 48.1 60.3 M12x1.75 84.3 19.0 33.7 26.1 35.4 32.0 43.8 54.8 75.9 70.0 87.7 M14x2 115 25.9 46.0 35.7 48.3 43.7 59.8 74.8 104 95.4 120 M16x2 157 35.3 62.8 48.7 65.9 59.7 81.6 94.2 130 102 141 130 163 M20x2.5 245 55.1 98.0 93.1 127 147 203 203 255 M24x3 353 79.4 141 134 184 212 293 293 367 M30x3.5 561 126 224 337 466 466 583 M36x4
817
184
327
490
678
678
850
1 Proof loads and tensile strengths are computed by multiplying the stresses given in Table 1 by the stress area of the thread.
2 Stress area = .7854 (D - 0.9382P)2 where D is nominal thread diameter in mm and P is thread pitch in mm.
5.2.5.2.1 The minimum hardness of the threaded wedge shall be HRC45. The length of the threaded section of the wedge shall be equal to the diameter of the stud. To facilitate removal of the broken stud, the wedge shall be counterbored. The thickness of the wedge at the thin side of the hole shall equal the diameter of the stud plus
the depth of counterbore. Threads for the wedge shall conform to the same standard as is specified for the threads on the product being tested, except Grade 4H tolerances (as described in ISO 965) shall apply. When testing studs having an interference fit thread, the wedge shall be threaded to provide a finger free fit. The supporting fixture, as shown in Figure 3 shall have a hole clearance over the nominal size of the stud, and shall have its top and bottom edges rounded or chamfered to the same limits specified for the hardened wedge in 5.2.5.1.
5.2.5.2.2 To meet the requirements of 5.1, the stud shall support a load not less than the minimum tensile strength specified for the applicable size, thread series, and class in Table 4 prior to stud fracture.
FIGURE 3 – WEDGE TEST DETAILS - STUDS
C = Clearance of hole
D = Diameter of stud
R = Radius or chamfer
T = D plus depth of counterbore
W = Wedge angle (See Table 4)
5.2.6 Testing of Machined Test Specimens
Where bolts, screws and studs cannot be tested in full size for proof load and tensile strength requirements, tests shall be conducted using test specimens machined from the bolts, screw of stud.
5.2.
6.1 A test specimen shall be turned from the bolt, screw or stud with the axis of the specimen located coincident with the axis of the bolt, screw or stud shank, and shall have dimensions as shown in Figure 4.
5.2.
6.2 The test specimen shall be tensile tested as described in 5.2.3 and the yield strength, tensile strength, elongation and reduction of area determined.
FIGURE 4 – TENSILSE TEST SPECIMEN FOR BOLTS OR SCREWS WITH TURNED DOWN SHANK
D = Diameter of turned down shank (D' G = Gage length = 50 A = Length of turned down shank = G + D' R = Fillet Radius (R ≥ 4 mm) The reduction of shank diameter of bolts, screws or studs of classes 8.8, 9.8 and 10.9 should not exceed 25 percent of the original nominal diameter of the product. The results in a cross sectional area of the turned down section of approximately 56 percent of the original diameter cross section area. 5.2. 6.3 To meet the requirements of 5.1, the test specimen must have a yield strength, tensile strength, elongation and reduction of area equal to or greater than the values for these properties specified for the applicable product size and class in Table 3. 5.3 MARKING 5.3.1 Bolts and Screws All metric bolts and screws, except internal drive head screws, with nominal diameters of M3.5 and larger shall be marked permanently and clearly to identify the property class and fastener manufacturer. Property class marking shall be as shown in Table 6, shall be located on the top of the head and may be raised or recessed unless otherwise ordered by the purchaser. When raised, markings shall project not less than 0.1 mm for M14 and smaller screws, and 0.3 mm for M16 and large screws, above the surface of the head, and height thereof shall conform to the following: Bolt or Screw Size (mm) Height of Symbol (mm) 3.5 – 6 1.5 8 – 10 2.3 12 and 14 3.2 16 and larger 4.0 Metric bolts and screws shall not be marked with radial line symbol. 5.3.2 Studs Studs with nominal diameters of M5 and larger shall be permanently and clearly marked to identify the property class. The symbols used shall be as given in Table 6. Markings shall be located on the extreme end of the stud, shall be as large as manufacturing permits (preferably as specified for bolts and screws in 5.3.1) and may be raised or depressed at the option of the manufacturer. For studs with an interference fit thread, the markings shall be located at the nut end. For studs smaller than M12 nominal diameter alternate symbols, as given in Table 6, may be used. TABLE 6 - PROPERTY CLASS IDENTIFICATION SYMBOL DX No. Property Class Bolts, Screws and Studs Optional for Studs Smaller than 12mm dia. DX520501 4.6 4.6 - DX520502 4.8 4.8 - DX520503 5.8 5.8 - DX520504 8.8 8.8 O DX520505 9.8 9.8 + DX520506 10.9 10.9 g 5.3.3 When specified by purchaser, bolts screws and studs with nominal diameters M5 and larger and left hand threads shall be marked with the symbol “ 10. INSPECTION AND REJECTION All materials supplied to this specification must comply with the requirements listed in DX000005. 11. APPROVED SOURCES Not applicable 12. REVISION RECORD Rev Date Description Approved By Title Signature 0 15 SE 99 Original Issue L. Gazzarato Chairman, Fasteners Specialist Team on file 0 15 SE 99 Original Issue D. L. Garrett, Jr. Delphi Materials Strategic Planning Manager on file