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Determine the correct washer dimensions based on bolt size and application. Find SAE and USS standard specifications for flat, fender, lock, and split lock washers.
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Standard flat washer
Larger diameter, lower pressure
Prevents loosening
Split ring design
| Aspect | SAE | USS |
|---|---|---|
| Full Name | Society of Automotive Engineers | United States Standard |
| Outer Diameter | Smaller | Larger |
| Thickness | Thinner | Same or thicker |
| Bearing Pressure | Higher | Lower |
| Common Use | Automotive, machinery | General construction |
Dimensions in inches for SAE standard flat washers:
| Bolt Size | Inner Diameter | Outer Diameter | Thickness |
|---|---|---|---|
| #4 | 0.113" | 0.281" | 0.049" |
| #6 | 0.141" | 0.328" | 0.049" |
| #8 | 0.172" | 0.375" | 0.049" |
| #10 | 0.201" | 0.438" | 0.049" |
| 1/4" | 0.281" | 0.563" | 0.063" |
| 5/16" | 0.344" | 0.688" | 0.063" |
| 3/8" | 0.406" | 0.844" | 0.063" |
| 1/2" | 0.531" | 1.125" | 0.095" |
| 5/8" | 0.656" | 1.406" | 0.095" |
| 3/4" | 0.781" | 1.625" | 0.095" |
Strength: High
Strength: High
Strength: Low
General purpose fastening. Use standard flat washers for most applications where load distribution is minimal.
High-stress environments with significant loads. Use lock washers or larger diameter washers to prevent loosening.
Load-bearing applications requiring maximum holding power. Use structural-grade washers with specified bearing area.
SAE washers have smaller outer diameters and higher bearing pressure, making them ideal for precision machinery. USS washers have larger outer diameters and distribute load over a wider area, making them better for soft materials or general construction.
Washers distribute the load of a fastener over a wider area, preventing the bolt head or nut from pulling through soft materials. They also help prevent loosening from vibration and improve overall joint integrity.
Bearing area is the surface area between the inner and outer diameter of the washer that makes contact with the fastened material. Larger bearing area distributes pressure more evenly and is better for soft materials.
Use flat washers for load distribution on stationary applications. Use lock washers (split lock or tooth lock) for vibration-prone applications where bolts might loosen, such as automotive or machinery applications.
Yes, stainless washers work well with steel bolts. However, avoid using steel washers with stainless bolts, as galvanic corrosion can occur. Always match materials when possible or use compatible combinations.
Always match the washer inner diameter to your bolt size. Use SAE washers for machinery and automotive applications, USS for construction and general applications where larger bearing area is beneficial.
Yes, there are ISO standards used internationally and various military specifications. SAE and USS are the most common in North America. Check your project requirements to determine which standard to use.
Place the washer on the fastener before inserting through the material. The washer should sit flat against the surface with the bolt head or nut on top. This ensures proper load distribution.
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