Ground lug washers, 2 hole?

Grounding lug washers are flat tab or plate shaped pieces that provide electrical continuity between fasteners and conducting surfaces. The "two hole" mount connects the conductor and the chassis to eliminate the ground from a single threaded point. Typically, one hole is used for the lug or cable crimp and one for the washer screw or stud. This maintains the electrical connectivity of the panel when serviced.
Grounding lug washers are electrical first and ornamental/structural second as opposed to decorative or structural washers. Raw load rating is less important than surface cleanliness, flatness and a clean, burr-free contact face. Contamination or micro-gaps can increase contact resistance and weaken the bond. Grounding washers are CNC machined from solid bar or plate stock, not stamped.

The Two-Hole Layout Beats the Single-Bolt Tab

As the bolt is torqued, a single-hole lug can rotate, slowly moving the conductor away from its specified position and perhaps loosening the joint. The 2 Hole Grounding Lug Washer adds a second fastening point to secure the plate to the substrate. The outcome is three practical benefits:

Anti-rotation: the second hole prevents washer spinning during torqueing, ensuring alignment from prototype to production.
Redundant contact prevents tilt-induced gaps by keeping the contact face flat against the surface with two attachment points.
Serviceability: Faster inspection and re-termination by removing the conductor-side fastener without spinning the washer.

Different from a square washer, which is designed for structural load bearing. Its bond integrity and reproducible alignment make the two-hole earthing washer a reliable field electrical bonding washer.

Custom Drawing-Based Hole Sizes

The boss spacing of each enclosure is different, and catalogue washers rarely match bespoke panels. Our 2 Hole Grounding Lug Washer is custom-made to your bore diameters, center-to-center spacing, and footprint because every job is different.
You set the variables; we machine them.

Conductor hole diameter: M4, M5, M6, or custom bore per drawing.

Determine chassis hole diameter and pattern (round, slot, or oval).

Adjust hole-to-hole pitch and edge distance to fit enclosure layout.

Available in length, width, and thickness from 0.5 to 15 mm upon order.

Chamfer, countersink, or edge-break each print.

Before cutting any metal, our English-speaking engineers analyse STEP, IGES, or DWG files for DFM (design for manufacturability), material, and tolerance. Most bespoke washers are prototyped in 5–7 days, volume produced in 10–18 days, and shipped to North America and Europe in 3–7 business days in export-grade packaging.

Materials Chosen for Conductivity and Corrosion Resistance

For a grounding washer, material choice drives both the electrical path and the service life. KEY-CNC machines these washers from stocked, traceable bar and plate:

Material	Key Properties	Recommended Grounding Use
Brass C360	Excellent machinability, natural conductivity	Electrical grounding, instrument panels, decorative hardware
Copper (on request)	Highest conductivity for low-impedance bonding	Where every milliohm of contact resistance counts - machined on request
Stainless Steel 316/316L	Superior chloride resistance, chemical stability	Marine, coastal, chemical processing
Stainless Steel 304	Good corrosion resistance, 520+ MPa tensile	General industrial, outdoor structures
Aluminum 6061-T6	Lightweight (2.7 g/cm³), 310+ MPa tensile	Weight-sensitive enclosures, electronics

Material certificates and CMM inspection reports are available on request for full traceability.

product-2500-299

Finishes That Protect the Bond, Not Just the Look

A grounding interface lives or dies by its contact resistance, so surface treatment is selected to keep the conduction path clean. In-house or partner-network finishing includes:

Passivation (citric/nitric) - removes free iron from stainless, extending corrosion life without adding a resistive layer.
Tin or nickel plating - improves solderability and lowers contact resistance for repeated mate cycles.
Anodizing (Type II/III) - for aluminum washers where abrasion and UV resistance are needed; the anodized film is non-conductive, so we mask the contact face or use a separate conductive path.
Powder coating - for outdoor and industrial parts where only the non-contact surfaces need protection.

All finishes are validated before shipment, and our engineers advise on which option keeps your bond low-impedance.

The Value of 2-Hole Grounding Lug Washers

Simple parts have a wide reach. CNC-machined grounding washer applications include:

Install solar PV racking by attaching rails and frames to the inverter earth.

Earthing antenna mounts and cabinet enclosures for telecom and broadcast towers.

Electrical panels and switchgear provide secure grounding in enclosures.

For marine and coastal equipment, corrosion-resistant bonding is necessary to prevent damage from salt air.

Verified low-impedance routes for safety grounding in EV charging and battery enclosures.

For outdoor lighting fixtures, secure luminaire housings to a grounded structure.

Verifiable Tolerances and Quality

Every washer leaves Shenzhen under ISO 9001:2015, RoHS-compliant, in-process and final inspection. Our 3-axis and 5-axis CNC centres maintain flatness to 0.02 mm and face parallelism to 0.01 mm, and CMM verifies essential dimensions. Our grounding washers have the same ±0.02–±0.05 mm capabilities as our robotic and medical customers, ensuring flat and burr-free contact surface.
KEY-CNC is a one-stop metal processing partner for CNC milling, turning, laser cutting, anodising, plating, and hardware insertion, with 16+ years of precision machining, 1,000+ cooperative clients, a 95%+ repeat order rate, and 1,200+ custom models delivered.