Side-by-Side Comparison
Washers & Retaining Rings
Fender Washers vs. Flat Washers
Comparing 2 standards across 20 specifications. 20 key differences identified.
Comparing:
Fender Washers
Flat Washers
Fender washers feature an oversized outer diameter approximately three times larger than their central hole (e.g. 1/4" ID × 1.0" to 1.25" OD), designed to bridge enlarged holes and distribute clamping force across thin sheet metal, automotive panels, and wood.
Standard flat washers distribute fastener clamp load and prevent surface embedding, standardized under DIN 125 (ISO 7089 Form A metric without chamfer) and ASME B18.22.1 (Type A Narrow, Regular, and Wide series in imperial sizes).
Specification Comparison Table
20 Parameters| Parameter / Spec | ||
|---|---|---|
|
Governing Standards
|
ASME B18.22.1 (Large Diameter Flat Washers) / SAE J485 | DIN 125 Form A (ISO 7089) / ASME B18.22.1 Type A |
|
Defining Characteristic
|
Outer diameter is ~3× to 4× the inner bolt diameter | — |
|
3/16" × 1.0" Fender Washer
|
ID: 0.219 in (5.6 mm) | OD: 1.00 in (25.4 mm) | Thickness: 0.050 in (1.27 mm) | — |
|
1/4" × 1.0" Fender Washer
|
ID: 0.281 in (7.1 mm) | OD: 1.00 in (25.4 mm) | Thickness: 0.062 in (1.57 mm) | — |
|
1/4" × 1.25" Fender Washer
|
ID: 0.281 in (7.1 mm) | OD: 1.25 in (31.8 mm) | Thickness: 0.062 in (1.57 mm) | — |
|
1/4" × 1.50" Fender Washer
|
ID: 0.281 in (7.1 mm) | OD: 1.50 in (38.1 mm) | Thickness: 0.062 in (1.57 mm) | — |
|
5/16" × 1.25" Fender Washer
|
ID: 0.344 in (8.7 mm) | OD: 1.25 in (31.8 mm) | Thickness: 0.062 in (1.57 mm) | — |
|
5/16" × 1.50" Fender Washer
|
ID: 0.344 in (8.7 mm) | OD: 1.50 in (38.1 mm) | Thickness: 0.062 in (1.57 mm) | — |
|
3/8" × 1.50" Fender Washer
|
ID: 0.406 in (10.3 mm) | OD: 1.50 in (38.1 mm) | Thickness: 0.062 in (1.57 mm) | — |
|
1/2" × 2.00" Fender Washer
|
ID: 0.531 in (13.5 mm) | OD: 2.00 in (50.8 mm) | Thickness: 0.078 in (1.98 mm) | — |
|
M3 Flat Washer
|
— | ID: 3.2 mm | OD: 7.0 mm | Thickness: 0.5 mm |
|
M4 Flat Washer
|
— | ID: 4.3 mm | OD: 9.0 mm | Thickness: 0.8 mm |
|
M5 Flat Washer
|
— | ID: 5.3 mm | OD: 10.0 mm | Thickness: 1.0 mm |
|
M6 Flat Washer
|
— | ID: 6.4 mm | OD: 12.0 mm | Thickness: 1.6 mm |
|
M8 Flat Washer
|
— | ID: 8.4 mm | OD: 16.0 mm | Thickness: 1.6 mm |
|
M10 Flat Washer
|
— | ID: 10.5 mm | OD: 20.0 mm | Thickness: 2.0 mm |
|
M12 Flat Washer
|
— | ID: 13.0 mm | OD: 24.0 mm | Thickness: 2.5 mm |
|
1/4" ASME Type A
|
— | ID: 0.281 in (7.1 mm) | OD: 0.625 in (15.9 mm) | Thickness: 0.065 in (1.65 mm) |
|
3/8" ASME Type A
|
— | ID: 0.406 in (10.3 mm) | OD: 0.812 in (20.6 mm) | Thickness: 0.065 in (1.65 mm) |
|
1/2" ASME Type A
|
— | ID: 0.531 in (13.5 mm) | OD: 1.062 in (27.0 mm) | Thickness: 0.095 in (2.41 mm) |