Torque Chart for 18-8 (304) and 316 Stainless Steel Fasteners
Torque Chart for 18-8 (304) and 316 Stainless Steel Fasteners
About Stainless Steel Fasteners
Stainless steel fasteners provide excellent corrosion resistance but have significantly different mechanical properties than carbon steel grades. Torque values for stainless are approximately 60-70% of Grade 5 values due to lower tensile strength and the critical need to prevent galling.
Common Stainless Grades
| Grade | Composition | Tensile Strength | Best For |
|---|---|---|---|
| 18-8 (304) | 18% Cr, 8% Ni | 70,000-85,000 PSI | General purpose, food equipment |
| 316 | 16% Cr, 10% Ni, 2% Mo | 75,000-90,000 PSI | Marine, chemical exposure |
| 410 | 12% Cr (martensitic) | 100,000+ PSI | Higher strength, less corrosion resistance |
Important: Unlike carbon steel grades (5, 8), stainless steel fasteners do not have standardized grade markings. Always verify material from supplier documentation.
18-8 Stainless Steel Torque Specifications (UNC)
⚠️ Critical: Always use anti-seize or thread lubricant with stainless fasteners
| Size | TPI | Dry Torque (ft-lbs)* | Dry Torque (Nm)* | Lubricated (ft-lbs) | Lubricated (Nm) | Clamp Load (lbs) |
|---|---|---|---|---|---|---|
| #6 | 32 | 1.0 | 1.4 | 0.8 | 1.1 | 210 |
| #8 | 32 | 1.8 | 2.4 | 1.4 | 1.9 | 330 |
| #10 | 24 | 2.8 | 3.8 | 2.1 | 2.8 | 475 |
| 1/4" | 20 | 5.4 | 7.3 | 4.1 | 5.6 | 1,250 |
| 5/16" | 18 | 11 | 15 | 8 | 11 | 2,000 |
| 3/8" | 16 | 20 | 27 | 15 | 20 | 2,950 |
| 7/16" | 14 | 32 | 43 | 24 | 33 | 4,050 |
| 1/2" | 13 | 48 | 65 | 36 | 49 | 5,400 |
| 9/16" | 12 | 72 | 98 | 54 | 73 | 6,950 |
| 5/8" | 11 | 97 | 132 | 73 | 99 | 8,600 |
| 3/4" | 10 | 170 | 230 | 128 | 174 | 12,750 |
| 7/8" | 9 | 170 | 230 | 128 | 174 | 17,500 |
| 1" | 8 | 235 | 319 | 176 | 239 | 23,000 |
*Dry torque for stainless is NOT recommended due to galling risk — values shown for reference only.
316 Stainless Steel Torque Specifications (UNC)
316 stainless provides similar strength to 18-8 with superior corrosion resistance, especially in marine and chemical environments.
| Size | TPI | Dry Torque (ft-lbs)* | Dry Torque (Nm)* | Lubricated (ft-lbs) | Lubricated (Nm) | Clamp Load (lbs) |
|---|---|---|---|---|---|---|
| #6 | 32 | 1.1 | 1.5 | 0.8 | 1.1 | 220 |
| #8 | 32 | 1.9 | 2.6 | 1.4 | 1.9 | 350 |
| #10 | 24 | 3.0 | 4.1 | 2.3 | 3.1 | 500 |
| 1/4" | 20 | 5.8 | 7.9 | 4.4 | 6.0 | 1,320 |
| 5/16" | 18 | 12 | 16 | 9 | 12 | 2,100 |
| 3/8" | 16 | 21 | 28 | 16 | 22 | 3,100 |
| 7/16" | 14 | 34 | 46 | 26 | 35 | 4,250 |
| 1/2" | 13 | 51 | 69 | 38 | 52 | 5,700 |
| 9/16" | 12 | 76 | 103 | 57 | 77 | 7,300 |
| 5/8" | 11 | 103 | 140 | 77 | 104 | 9,100 |
| 3/4" | 10 | 180 | 244 | 135 | 183 | 13,500 |
| 7/8" | 9 | 180 | 244 | 135 | 183 | 18,500 |
| 1" | 8 | 250 | 339 | 188 | 255 | 24,000 |
⚠️ GALLING: The #1 Stainless Steel Fastener Problem
Galling (also called "cold welding") occurs when stainless steel threads seize during installation. The high friction generates heat, causing the metal to literally weld itself together. Once galled, the fastener is destroyed and often requires cutting or drilling to remove.
Why Stainless Galls
1. Soft, ductile material — deforms under pressure
2. Protective oxide layer — when broken, exposes reactive base metal
3. Poor heat dissipation — friction heat builds rapidly
4. Self-mating surfaces — similar metals have highest galling tendency
Galling Risk Factors
| Factor | Lower Risk | Higher Risk |
|---|---|---|
| Speed | Slow installation | Fast/power tool installation |
| Lubrication | Well-lubricated | Dry threads |
| Thread fit | Looser (2A/2B) | Tighter (3A/3B) |
| Surface finish | Smooth, polished | Rough, machined |
| Temperature | Cool | Hot or friction-heated |
| Material match | Dissimilar alloys | Same alloy (304 into 304) |
Galling Prevention: Required Practices
1. Always Use Anti-Seize Compound
This is not optional for stainless steel fasteners.
| Anti-Seize Type | Temperature Range | Best For |
|---|---|---|
| Copper-based | -65°F to 1800°F | General purpose, high temp |
| Nickel-based | -65°F to 2400°F | Stainless-to-stainless, food-safe |
| Aluminum-based | -60°F to 1600°F | Prevents galvanic corrosion |
| Molybdenum (Moly) | -65°F to 750°F | High-pressure applications |
Application: Apply thin, even coating to male threads only. Excess compound can contaminate joints or attract debris.
2. Slow Installation Speed
- Hand-start all stainless fasteners — never power-drive from first contact
- Run down with minimal pressure — let threads engage naturally
- Final tighten slowly — fast rotation = heat = galling
- If resistance increases suddenly — STOP — back off immediately
3. Use Proper Thread Fit
| Thread Class | Description | Galling Risk |
|---|---|---|
| 2A/2B | Standard fit | Lower — preferred for stainless |
| 3A/3B | Close fit | Higher — avoid when possible |
4. Consider Dissimilar Alloys
Threading 316 bolts into 304 nuts (or vice versa) reduces galling compared to identical alloy combinations.
Torque Reduction with Anti-Seize
When using anti-seize compounds on stainless fasteners, reduce torque by 25-35% from dry values:
| Condition | Torque Factor |
|---|---|
| Dry (not recommended) | 100% (reference only) |
| Light oil | 85% |
| Anti-seize (copper) | 75% |
| Anti-seize (nickel) | 75% |
| Moly-based lubricant | 65-70% |
Use the "Lubricated" column values in the tables above when using any anti-seize or lubricant.
75% Rule for Stainless Applications
⚠️ For critical applications, use 75% of lubricated values.
Stainless fastener torque is already conservative, but for:
- Pressure vessels
- Food/pharmaceutical equipment
- Marine applications
- Repeated assembly/disassembly
Calculate: Lubricated value × 0.75
Example: 1/2"-13 18-8 stainless
- Lubricated: 36 ft-lbs
- 75% value: 27 ft-lbs
Thread Engagement for Stainless
Stainless steel's lower strength requires adequate thread engagement:
| Mating Material | Minimum Engagement |
|---|---|
| Stainless Steel | 1.5× bolt diameter |
| Carbon Steel | 1.0× bolt diameter |
| Aluminum | 2.0× bolt diameter |
| Plastic | 2.5× bolt diameter (caution with loads) |
Safety Warnings
⚠️ IMPORTANT SAFETY INFORMATION
1. Never Install Stainless Dry — Galling can occur instantly and destroy both fastener and mating threads.
2. Hand-Start Always — Cross-threading is more common with stainless due to its softness.
3. Don't Force It — If a stainless fastener binds during installation, stop immediately. Back it out and inspect threads.
4. Strength Limitations — Stainless provides 60-70% the strength of Grade 5. Never substitute stainless for Grade 5 or 8 in structural applications without engineering review.
5. Magnetic Testing — 18-8 and 316 are generally non-magnetic when annealed. Slight magnetism may occur from cold working but doesn't indicate carbon steel substitution.
6. Corrosion Is Not Zero — "Stainless" resists corrosion but can still corrode in certain environments (chlorides, acids). Match alloy to environment.
When to Choose Stainless vs. Carbon Steel
| Application | Recommended |
|---|---|
| Outdoor/weather exposure | Stainless (316 for coastal) |
| Food processing equipment | Stainless (18-8 or 316) |
| Marine environment | 316 Stainless |
| Chemical exposure | 316 Stainless (verify compatibility) |
| High-strength structural | Grade 5 or 8 (with plating if needed) |
| Automotive mechanical | Grade 5 or 8 |
| Decorative/aesthetic | Stainless |
| Cost-sensitive, dry indoor | Grade 5 with zinc plating |
Additional Resources
- [Grade 5 Torque Chart](/charts/torque-chart-grade-5)
- [Grade 8 Torque Chart](/charts/torque-chart-grade-8)
- [Metric Torque Specifications](/charts/torque-chart-metric)
- [Torque Basics Guide](/guides/torque-basics)
- [Anti-Seize Selection Guide](/guides/anti-seize-selection)
Last Updated: 2025
Data based on ASTM F593 and manufacturer specifications
Stainless steel torque values vary by manufacturer — always verify for critical applications