We supply hot dip galvanized grade 4.8 hex bolts: true HDG zinc ≥45µm (ISO 1461) on carbon steel, giving your outdoor connections real corrosion life at an economical price. We deliver full (DIN933) and half (DIN931) thread, M6–M36 (UNC optional), ship bolt + galvanized nut + flat/spring washer sets, die-cut the coated thread so nuts never jam, and attach MTC, COA and salt-spray (ISO 9227) reports with every batch. OEM marking, ready stock and free samples are available on request.
Comprehensive Product Specification
| Category | Specification |
|---|---|
| Standard | DIN933 (full) / DIN931 (half) / ISO4017 / GB5783 |
| Head | Hexagonal head |
| Material | Carbon steel (SWRCH10/22A) |
| Grade | 4.8 (ISO 898-1) |
| Coating | Hot-dip zinc ≥45µm (ISO 1461); plating optional |
| Thread after coating | Die-cut / cleaned to 6g fit |
| Size | M6 – M36 metric coarse (UNC optional) |
| Matching parts | Galvanized 4.8 nut + flat / spring washer |
| Use | Guardrail, scaffold, fence, tower, outdoor trim |
| Packing | PE bag → carton ≤25kg → pallet / case |
| Lead time | Stock 7–10 d; custom 10–15 d |
| Trade terms | FOB / CIF / CFR / EXW / DDP |
| Certificates | Invoice, P/L, MTC, COA, salt-spray report |
Why Choose Grade 4.8 Galvanized Hex Bolts?
Real Corrosion Protection Where It Counts
Hot-dip galvanizing forms a metallurgically bonded zinc layer (min 45µm) that continues to protect even where scratched - the right choice where road salt, rain and industrial atmospheres meet.
01
Economic Strength
At 400 MPa tensile and HB 110–145 hardness, grade 4.8 covers handrails, screening, brackets and cladding trim.
02
Coated Thread That Actually Fits
We die-cut the galvanized thread and hold a 6g tolerance, so bolts and nuts run together smoothly - no jammed, time-wasting installation on site.
03
Complete Galvanized Sets
Matching galvanized 4.8 nuts and flat/spring washers ship in the same box, so electrochemical potential and fit are consistent across the whole joint.
04
Traceable Down to a Heat & Batch Number
Every delivery carries MTC, COA and salt-spray reports, so your project owner and inspector can verify coating thickness and mechanical properties in seconds.
05
DIN933 Full-Thread Dimension Table (Grade 4.8)
| Size d | Pitch p | Across Flats s | Head Height k | Common Stock Length (mm) |
|---|---|---|---|---|
| M6 | 1.00 | 10 | 4.0 | 20–100 |
| M8 | 1.25 | 13 | 5.3 | 25–150 |
| M10 | 1.50 | 17 | 6.4 | 30–200 |
| M12 | 1.75 | 19 | 7.5 | 35–250 |
| M14 | 2.00 | 22 | 8.8 | 40–250 |
| M16 | 2.00 | 24 | 10.0 | 40–300 |
| M18 | 2.50 | 27 | 11.5 | 50–300 |
| M20 | 2.50 | 30 | 12.5 | 50–350 |
| M22 | 2.50 | 34 | 14.0 | 60–350 |
| M24 | 3.00 | 36 | 15.0 | 60–400 |
Note:typical metric values for reference - confirm exact dimensions against your drawing before ordering.
Tightening Torque Reference (Grade 4.8)
Economical torques for galvanized 4.8 bolts, dry assembly (µ≈0.14). Reduce by roughly 20% when threads are lubricated.
| Size d | Torque (N·m, dry) | Torque with Lubricant |
|---|---|---|
| M6 | 5–6 | 4–5 |
| M8 | 12–15 | 9–12 |
| M10 | 24–30 | 19–24 |
| M12 | 42–52 | 33–42 |
| M16 | 105–125 | 84–100 |
| M20 | 200–240 | 160–190 |
| M24 | 340–410 | 270–330 |
Note:reference values only - always tighten with a calibrated torque wrench per your structural design and the friction condition on site.
Hot-Dip Galvanized Coating - How It Protects
Metallurgical Bond, Self-Healing Action
HDG is an alloyed zinc-iron layer (min 45µm), not a plate - at a scratch the surrounding zinc sacrifices itself to keep protecting the steel.
Verified Every Batch
Zinc thickness per ISO 1461 and neutral salt-spray per ISO 9227 are measured and reported with each delivery.
Thread Re-Cut After Galvanizing
After zincing we re-cut the thread to a free-running 6g fit, so the coating does not jam nut assembly.
Note:white rust on fresh HDG in the first storage weeks is cosmetic, not structural - store with drainage and airflow and it cures on its own.
Grade 4.8 vs Grade 8.8 - Which to Spec?
The strongest debate on a fastener drawing is usually 4.8 vs 8.8, not the coating. Both can be hot-dip galvanized; the difference is the load they take and the cost:
| Property | Grade 4.8 | Grade 8.8 |
|---|---|---|
| Tensile strength | ≥400 MPa | ≥800 MPa |
| Yield strength | ≥320 MPa | ≥640 MPa |
| Heat treatment | None (economical) | Quenched & tempered |
| Typical joint | Secondary, trim, cladding | Primary, shear-bearing, seismic |
| Relative price | Low - best economy | Higher - for loaded joints |
| Hardness | HB 110–145 | HB 255–336 |
Rule of thumb: for handrails, fences, brackets and light connections, galvanized 4.8 gives the best value. Where the joint carries primary or shear load - column-to-beam nodes - move up to galvanized 8.8 and specify the correct preload.
Note on galvanized 8.8: high-strength grades are more sensitive to hydrogen embrittlement after galvanizing - we manage pickling and baking for 8.8 to avoid delayed fracture.
Applications of Hot Dip Galvanized 4.8 Hex Bolt
| Steel Structure / Component | Exact Bolt Location | Why It Fits |
|---|---|---|
| Highway / bridge guardrail | Wave-form rail to post brackets (M16/M20), end anchors, splices | HDG stands up to road salt and rain on the rail-to-post connection. |
| Scaffolding frames | Couplers, ledger-to-standard joints, base plates, diagonal braces | Reusable, rust-resistant joints that disassemble cleanly. |
| Panel & chain-link fences | Hinge side & latch side of gates, post caps, brace rails | Outdoor hinges and brackets that must not seize or rust. |
| Transmission / telecom towers | Secondary bracing members, step brackets, conductor fittings | Decades of weather on tower secondary joints. |
| Farm & greenhouse steel | Greenhouse frame-to-cladding clamps, livestock pen panels | Damp, aggressive atmospheres demand real zinc protection. |
| Solar / PV mounting | Module rail-to-purlin brackets, end clamps, mid clamps | Year-round exposure calls for coatings that keep working. |
| Light steel frames | Purlin-to-girt splices, trim & flashing, base cleats | Economical, corrosion-safe connection for cladding trim. |
Our Quality Control
| Check | Detail |
|---|---|
| Zinc thickness | Magnetic gauge per ISO 1461, ≥45µm |
| Salt-spray test | NSS per ISO 9227, report per batch |
| Thread fit | Go/No-Go gauge; runs freely with nut |
| Strength | Tensile & hardness per ISO 898-1, MTC issued |
| Coating adhesion | Pounding check; no flaking on HDG |
Packing, Delivery & Transport
| Inner packing | PE bag + anti-rust paper, carton/label as ordered |
| Outer packing | Carton ≤25kg → stretch-wrap + pallet / case |
| Sample | 3–5 days ready |
| Lead time | Stock 7–10 d; custom 10–15 d |
| Documents | Invoice, P/L, MTC, COA, salt-spray report, CO |
FAQ:
Will it rust?
HDG ≥45µm shields for decades rural, years coastal - far better than thin electro-zinc.
Do you supply nuts and washers?
Yes - matched galvanized 4.8 nuts and washers ship together.
Won't the coating jam the threads?
We die-cut the coated thread to a 6g fit, so installation runs freely.
Is 4.8 strong enough for my project?
For light and secondary steel connections yes; for primary joints use 8.8/10.9.
MOQ and price?
MOQ 500 pcs; sample available. Send size, quantity and destination for a quote.
