4190.01 STRUCTURAL ALUMINUM.
Structural aluminum shall meet requirements specified in the contract documents. All structural aluminum shall be welded using the metal inert gas (MIG) process, unless otherwise approved by the Engineer.

4190.02 ALUMINUM FASTENERS.
Aluminum bolts, nuts, and washers shall be of the size shown in the contract documents.

A. Bolts.
Bolts shall be made from rods meeting requirements of ASTM B 211, Alloy 2024-T4. Unless otherwise specified, bolts shall have hexagonal heads conforming to ANSI B18.2.1, and threads shall conform to ANSI B1.1 for Unified Coarse Thread Series, Class 2A fit, except that bolts for fastening together structural aluminum parts shall have heavy hexagonal heads.

B. Nuts.
Nuts shall be manufactured from stock meeting requirements of ASTM B 211, Alloys 6061-T6 or 6262-T9. Unless otherwise specified, nuts shall be hexagonal conforming to ANSI B18.2.2, and threads shall conform to ANSI B1.1 for Unified Coarse Thread Series, Class 2B fit, except that nuts for fastening together structural aluminum parts shall be heavy hexagonal nuts.

Self locking nuts shall be of a type and quality approved by the Engineer.

C. Washers.
Washers shall be made from a material of a quality suitable for the intended use and approved by the Engineer. Unless otherwise specified, washer dimensions shall meet requirements of ASTM F 436.

4190.03 BRONZE BEARING METAL.
All bronze bearings shall be of the shape and dimensions shown in the contract documents. Bearing surfaces shall be finished to the degree specified. Bronze metal for plain bearings shall meet requirements of ASTM B 22, Alloy UNS No. C91300 or C91100, or ASTM B 100.

When lubricated bronze bearings are specified, the metal shall be bronze meeting requirements of ASTM B 22, Alloy UNS No. C91300, C91100, or C86300, or ASTM B 100. In each bearing surface, 24 to 35% of the area shall consist of dry lubricating inserts not less than 3/16 inch (5 mm) deep. These inserts shall be arranged in a geometric pattern such that successive rows overlap in the direction of movement, shall be so distributed along the rows that, in any two adjacent rows, the entire width of the bearing surface will be covered, except 1/4 inch (6 mm) at each margin, and shall be a graphite type of lubricant held by a suitable lubricating binder which shall be firmly compacted into the recess.

The sliding surface shall be flat within 1/32 inch per foot (3 mm/m) on length or width. Radial, cylindrical, or spherical sliding surfaces shall have a tolerance not exceeding 0.010 inch (0.254 mm) on the radius. Convex surfaces shall have a positive radial tolerance not exceeding 0.010 inch (0.254 mm).