Gibraltar Z8820 M20 Extra Thick Flat Washer Black Oxide

Product Description

The GIBRALTAR Z8820 is an M20 extra thick flat washer manufactured from case-hardened 1010 steel with a black oxide finish. It is designed to distribute fastener load across a wider bearing surface in bolted assemblies where standard-thickness washers are insufficient. The black oxide finish provides a moderate level of corrosion resistance and reduces light reflection in finished assemblies. With an inside diameter of 21 millimeters, an outside diameter of 35 millimeters, and a thickness of 3.5 millimeters, this washer meets metric fastener specifications for M20 hardware. It is a common component in structural, mechanical, and industrial assembly work handled by millwrights, maintenance technicians, and construction tradespeople.

This washer is suited for use in structural bolted connections, machinery mounting, heavy equipment assembly, and general industrial fastening applications where extra load distribution or added bearing surface thickness is required. The metric sizing makes it appropriate for equipment manufactured to ISO or metric DIN standards. It is sold individually and is compatible with M20 bolts and screws in both through-hole and tapped applications.

Key Features

• Extra thick profile at 3.5 millimeters provides increased load distribution compared to standard flat washers
• Case-hardened 1010 steel construction resists deformation under high clamping loads
• Black oxide finish offers moderate corrosion resistance and a low-glare appearance
• M20 screw size with 21 millimeter inside diameter for consistent metric fitment
• 35 millimeter outside diameter provides a broad bearing surface
• Metric system of measurement aligns with ISO and DIN fastener standards

Compatibility

Designed for use with M20 metric bolts and screws in structural, mechanical, and industrial fastening applications requiring an extra thick flat washer with a black oxide finish.

Installation Notes

Installation is performed by millwrights, maintenance technicians, or construction tradespeople using standard metric hand tools and torque wrenches. Always verify that the washer inside diameter, outside diameter, and thickness are appropriate for the joint design before assembly. Follow applicable fastener torque specifications for M20 hardware as defined by the equipment manufacturer or applicable structural codes. Inspect the washer for surface defects or deformation before installation.