SAE J429 Grade 8 Bolts
SAE J429 Grade 8 — the high-strength inch-series alloy grade: 150 ksi minimum tensile, 130 ksi yield and 120 ksi proof load across the full 1/4″ through 1-1/2″ range at C33–C39, with no diameter drop. Six radial head lines.
Last updated: 2026-11
Specifications
Grade 8 is the top of the SAE system: a quenched-and-tempered medium-carbon alloy steel marked with six radial lines, held at 150 ksi minimum tensile across the entire 1/4″–1-1/2″ range — the collected specification is explicit that there is no diameter step, unlike Grades 2 and 5, because the alloy content (Cr, Ni, Mo or V) and the hardenability it buys keep the through-section property where a plain carbon grade loses it. The trade-offs are real and the specification states them: the higher hardness that carries 150 ksi also makes the bolt more notch-sensitive, and under cyclic or impact loading a Grade 5 bolt at the same installed tension can be the more fatigue-tolerant choice. Grade 8 costs roughly 25–40% more than Grade 5; for static high-load joints that buys more margin per bolt, and for cyclic ones it deserves a second look before it is specified. The ASTM counterpart is A354 Grade BD; the matched nut is J995 Grade 8 or A563 DH with F436 hardened washers.
| Standard | SAE J429 Grade 8 — mechanical and material requirements for externally threaded inch-series fasteners |
|---|---|
| Head marking | 6 radial lines, plus the manufacturer symbol |
| Material | Medium-carbon alloy steel (alloying from Cr, Ni, Mo or V), quenched and tempered to higher hardness than Grade 5 |
| Min. tensile | 150 ksi across the full range — 1/4″ through 1-1/2″, no diameter drop |
| Min. yield | 130 ksi across the full range |
| Min. proof load | 120 ksi across the full range |
| Hardness | Rockwell C33–C39 (HRC) |
| Size range | 1/4″ through 1-1/2″ — no mechanical step anywhere in the range |
| Typical pairing | SAE J995 Grade 8 or ASTM A563 Grade DH nut; F436 hardened washer |
| ASTM counterpart | Functionally equivalent to ASTM A354 Grade BD (high-strength alloy Q&T at 150 ksi) |
Materials
- Medium-carbon alloy steel (Cr/Ni/Mo/V alloying), quenched and tempered
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (SAE J429 Grade 8 Bolts) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantity is 1,000–10,000 pieces depending on size. Stock items run 3–7 days. High-strength and custom parts run 15–25 days. Quantities or variants outside the standard range are confirmed at quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
Is Grade 8 always the upgrade from Grade 5?
For static loading, yes in margin: 150 ksi vs 120 ksi tensile means more clamping force or less weight for the same load, at roughly 25–40% higher cost. The collected comparison is explicit about the exception: under cyclic or impact loading the higher hardness makes Grade 8 more notch-sensitive, and it can be less fatigue-tolerant than a Grade 5 bolt at the same installed tension — the table lists "cyclic or impact loading; marginal lubrication" under when NOT to upgrade. Decide by load character, not by strength table alone, and keep the substitution decision with the drawing's engineer rather than upgrading at the counter.
What makes Grade 8 hold 150 ksi at 1-1/2″ when other grades step down?
Alloy content and quench-and-temper. Grade 2 loses strength above 3/4″ and Grade 5 above 1″ because thick plain-carbon sections do not through-harden; Grade 8's alloying (chromium, nickel, molybdenum or vanadium per the collected chemistry note) gives the hardenability to hit C33–C39 and 150 ksi tensile through the full 1/4″–1-1/2″ range. That is also why the matched hardware is non-negotiable: A563 Grade DH nuts and F436 hardened washers are what keep the joint failing in the bolt, not in a softer nut or a washer that dishes under preload.
What is the MOQ and lead time for this bolt grade?
The minimum order quantity is 1,000–10,000 pieces depending on size. Stock items ship in 3–7 days; high-strength and custom parts in 15–25 days. Common diameters in this grade are widely stocked; confirm the exact schedule against quantity and size mix at quotation.
What should an RFQ for this bolt grade state?
State the standard and grade (for example ISO 4017 Class 8.8 or ASTM F3125 Grade A325 Type 1), diameter and length, thread type (metric coarse or UNC/UNF), finish (plain, zinc, or hot-dip galvanized where the grade permits), required certificates such as a mill test report per EN 10204 3.1, and quantity per size — plus destination country.
Related knowledge
- What Bolt Property Classes 8.8, 10.9 and 12.9 Encode — and When High Strength Stops Being the Right Choice
- Bolt Grade Selection: ISO 898-1 8.8/10.9/12.9 vs ASTM A307 and A325
- 8.8 vs 10.9 vs 12.9 Bolts: Strength, Hardness and Cost — What the Evidence Settles
- Calculating Bolt Preload and Clamp Force: Torque, Friction and Tightening Method
- How to Determine Tightening Torque and Choose a Tightening Method for a Bolted Joint
- Fastener Failure Modes: Which Fatigue, Creep and SCC Controls the Evidence Supports
- Hydrogen Embrittlement in High-Strength Bolts: Which Grades Need Controls, Which Coatings and Baking Schedules Are Acceptable, and What to Require Before the RFQ
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support