INTERN MPAPS F-1053 PDF

This specification covers the requirements for manufacture, coating, mechanical properties, microstructure, chemical composition, quality, quality plan and source approval and quality control. Recommended steel grades are given in Section A.0 - General Information.

Restricted Chemical Substances

All product supplied to the requirements of this specification must comply with the requirements of the MPAPS B-50 specification.

APPLICATION

This specification covers two types (Type A and Type B) of high strength U-Bolts used to fasten springs, fifth wheels, tow loops, and similar parts, where higher clamp load capacity is required. Both types of U-Bolts can be provided as either quenched and tempered (Q&T) products or as cold-drawn and stressrelieved (CDSR) products. The new Type B U-Bolt exhibits higher strength properties.

Type A

Type A is the traditional MPAPS F-1053 U-Bolt. It may be provided as either a Q&T or CDSR product. It provides high strength (equivalent to the obsolete SAE Grade 7) properties as indicated in Section 4.3. Type A U-bolts, CDSR, ¾” dia and smaller, will meet the mechanical property requirements of Grade 8.1 studs as shown in Table 1 for Type B material.

NOTE: For all existing Engineering drawings (and/or part numbers) that reference this specification without designating a material TYPE, Type A U-Bolt product shall be supplied, unless otherwise specified on the Engineering drawing as MPAPS F-1053 U-Bolt, Q&T, with SAE Grade 8.1 mechanical properties.

Type B

Type B is a new higher strength U-Bolt (having strength properties equivalent to SAE Grade 8.1) as indicated in Section 4.3. It may be provided as either a Q&T or CDSR product.

Restriction on Application of Type B

Application of the Type B material is restricted to the “round-top” series of U-Bolts, designated as STYLE 065 (See Eng. Dwg 453945C1). The Type B material shall not be applied to any of the “flattop” series of U-Bolts designated as either STYLE 050 (see Eng. Dwg 453872C1) or STYLE 060 (see Eng. Dwg 453892C1). The Type B material shall not be provided for any U-Bolt part whose Engineering drawing does not specify U-Bolt Type B. All new Engineering drawings for U-Bolts must specify a bolt Type as: U-Bolt Type A or U-Bolt Type B.

Preferred Manufacturing Process

Types A and B U-Bolts may be manufactured using either the Q&T or CDSR process. The CDSR process provides improved resistance to fatigue loading and is the preferred manufacturing process.