S-91138A927 0.188" ID x 0.438" OD ASME B18.21.1 Plastic Washers

Key Features & Benefits at a Glance

• Exceptional thermal stability with a wide operating range from -30°F to 450°F, ensuring reliable performance in extreme temperature environments
• Superior mechanical strength with Rockwell M114 hardness for enhanced durability and resistance to deformation under load
• Precision dimensional fit with 0.188" ID and 0.438" OD designed specifically for No. 8 screws, providing secure fastening and vibration resistance
• Compliance with industry standards including ASME B18.21.1, ensuring consistent quality and interchangeability in industrial applications
• Environmental regulation adherence with RoHS 3 and REACH compliance, making them suitable for regulated industries and international markets
• Chemical and moisture resistance inherent to Ultem PEI plastic material, preventing corrosion and maintaining integrity in harsh conditions
• Lightweight yet robust construction offering excellent strength-to-weight ratio for applications where metal alternatives may cause galvanic corrosion or add unnecessary mass

Professional Applications & Engineering Value

These Ultem PEI plastic flat washers deliver critical engineering solutions for demanding environments where traditional metal components fail. The high-temperature resistance up to 450°F makes them ideal for aerospace, automotive, and electronics applications involving thermal cycling or proximity to heat sources. Their exceptional hardness (Rockwell M114) ensures maintained clamping force and surface protection even under sustained mechanical stress. The precise inch-system dimensions (0.188" ID x 0.438" OD) engineered for No. 8 screws prevent loosening in vibrating machinery while the non-conductive, corrosion-resistant properties of Ultem PEI eliminate galvanic compatibility issues in multi-material assemblies. These washers solve critical challenges in chemical processing, medical equipment, and electrical enclosures where temperature extremes, chemical exposure, and regulatory compliance are paramount concerns.

Specification Summary & Compliance

Manufactured to ASME B18.21.1 specifications with dimensional accuracy for inch-system applications. Features precise internal diameter (0.188"), outer diameter (0.438"), and thickness range (0.020-0.060") optimized for No. 8 screws. Compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring environmental safety and regulatory acceptance. The material properties include Rockwell M114 hardness and operational temperature range from -30°F to 450°F, validated through standardized testing protocols.