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SAE J773-2016: Complete Guide to Conical Spring Washers
Understanding Conical Spring Washers and Their Types
The SAE J773-2016 standard specifies two types of general purpose conical spring washers: Type L and Type H. These are available in narrow, regular, and wide series to provide appropriate load distribution. Type L washers are designed for use with SAE Grade 1 and 2 bolts, flattening at approximately 27,500 psi bolt stress. Type H washers are for SAE Grade 5 bolts, flattening at 60,000 psi. The spring return helps maintain bolt tension despite wear, thermal expansion, or compression set. Peripheral teeth can be added for non-slip or grounding applications.
| Washer Type | Intended Bolt Grade | Flattening Bolt Stress | Hardness (HRC) |
|---|---|---|---|
| Type L | SAE Grade 1 & 2 | 27,500 psi | 44–48 (loose) |
| Type H | SAE Grade 5 | 60,000 psi | 44–48 (loose) |
| Pre‑assembled washers: 40–48 HRC | |||
Design Considerations and Best Practices
The desired installed position is near flat. For proper function, ensure at least 70% of the washer annular area is bearing when supported on a full periphery. Over slots, the slot width should not exceed 1.5 times the inside diameter. Narrow series washers must always be fully supported. Insufficient bearing reduces spring return. Material is SAE 1050–1065 carbon steel, heat treated to 44–48 HRC (loose) or 40–48 HRC (pre‑assembled). After electroplating, baking at 400°F is required to relieve hydrogen embrittlement. Washers must pass a recovery test retaining at least one‑third original crown height after flattening.
🛠️ Key Insight: Conical spring washers are particularly effective in applications where bolt tension may be lost due to wear, thermal cycling, or compression set. Their high supporting load and spring return make them reliable in demanding environments.
⚠️ Critical: If a washer is not baked after plating, hydrogen embrittlement can lead to cracking and failure. Always follow the standard’s baking requirements at 400°F.
Frequently Asked Questions
- What are the two types of conical spring washers and for which bolt grades are they intended?
Type L washers are for SAE Grade 1 and 2 bolts; Type H washers are for SAE Grade 5 bolts. - What is the recommended installed position of the washer?
Ideally, the washer should be nearly flat when tightened. This occurs at specified bolt stresses for each type. - How can hydrogen embrittlement be prevented?
Electroplated washers must be baked at 400°F as soon as possible after plating to relieve hydrogen. - Can conical spring washers be used with oversize holes?
Yes, but ensure at least 70% of the washer area is supported. For slots, width should not exceed 1.5 times the ID. Narrow series should always be fully supported.
