Sh. Flange Bolt6*50

This aftermarket flange bolt is manufactured for the SYM Symphony 125I ST 125cc, compatible with 2017-2020 model years and cross-referenced to OEM number 96001-06050-02. Flange bolts integrate the washer function into the head design, reducing parts count and assembly time while providing more consistent preload distribution across the joint surface.

The integrated flange on this bolt serves multiple functions that improve joint reliability compared to standard hex head bolts with separate washers. The flange diameter of approximately 14mm for M6 bolts distributes the clamping force over 150mm² of bearing area, compared to just 28mm² for a standard hex head. This 5x increase in bearing area reduces surface pressure on aluminum castings from 200 MPa to 40 MPa, preventing the galling, embedding, and surface creep that can cause joint relaxation over time. The serrated underside of the flange bites into the mating surface, creating mechanical resistance to rotation that supplements the bolt’s clamp load. This is particularly valuable on joints subject to vibration, such as engine covers, transmission cases, and chassis brackets.

The bolt is manufactured from medium carbon steel (C35) with a minimum tensile strength of 800 MPa (property class 8.8). The threads are rolled after heat treatment to achieve a smooth surface finish (Ra <1.6μm) that reduces friction during torque application and improves fatigue life. The head is cold-forged to precise dimensional tolerances, with the flange concentric to the shank within 0.1mm to ensure even load distribution. The zinc phosphate coating provides basic corrosion protection while also acting as a lubricant during torque application, improving torque-tension consistency by 15-20% compared to uncoated bolts. Technical specifications: size 6x50; thread pitch 1.0mm (M6) or 1.25mm (M8); property class 8.8; tensile strength >800 MPa; head type: hex flange per ISO 4161; flange diameter 14mm (M6) or 18mm (M8); coating: zinc phosphate; temperature range -40°C to 120°C.

Application on the SYM Symphony 125I ST includes engine cover attachment, transmission case assembly, fuel tank mounting, and various chassis bracket connections. The flange bolt is particularly advantageous in applications where space constraints prevent the use of a separate washer, or where assembly line efficiency demands fewer parts to handle. During installation, torque to the OEM specification using a calibrated torque wrench. The serrated flange may leave marks on painted or polished surfaces—use a flat washer under the flange if surface appearance is critical. Inspect flange bolts during routine maintenance for signs of loosening (rust streaks from fretting corrosion) and replace if the serrations are worn smooth.