The FB-47 Friction Bolt (also known as 47mm Split Set Stabilizer or 47mm Friction Stabilizer) is the most widely used heavy-duty friction bolt in underground mining, tunneling, and ground support projects worldwide. With a 47mm outer diameter, high-strength micro-alloyed steel construction, and typical yield strength of 345–445 MPa (120–153 kN), the FB-47 delivers immediate full-length frictional anchorage upon installation without requiring resin, grout, or tensioning. This comprehensive technical guide from Tanrimine (TRM) — a China-based friction bolt manufacturer with 10+ years of experience, 30,000-ton annual capacity, and ISO9001 certification — covers every critical aspect: complete mechanical specifications, hole diameter vs anchorage force data, installation procedures and drive time optimization, hot-dip galvanizing corrosion protection, pull test methodology using hollow ram hydraulic jacks, and a detailed FB-47 vs FB-39 vs FB-33 comparison for B2B procurement decision-making.
In underground mining, tunnel reinforcement, and slope stabilization projects, selecting the right ground support bolt is a life-safety decision. The FB-47 Friction Bolt is the heavy-duty standard — specified in deep mines, high-stress rock conditions, and jumbo development headings where smaller bolts cannot deliver sufficient anchorage. This guide consolidates everything a mining engineer, procurement manager, or contractor needs to know about the FB-47: from raw material to installation to pull testing.
Tanrimine Metal Support Co., Ltd. (TRM) is a professional friction bolt manufacturer with an annual production capacity of 30,000 tons. Operating under ISO9001 quality management, TRM produces a full range of friction bolts (FB-33, FB-39, FB-47), anchor plates (dome, combi, duo, strata, flat, mesh), mesh, support rings, pull collars, and accessories. Our products are exported to Australia, South Africa, Russia, and Asian markets, serving some of the world's largest mining companies. With a self-owned galvanizing production line, TRM ensures superior zinc coating quality and corrosion resistance for every bolt.
The FB-47 Friction Bolt is a longitudinally slotted high-strength steel tube with a 47mm outer diameter, designed as a full-length friction rock reinforcement system. It is installed by driving the bolt into a pre-drilled hole slightly smaller than the bolt diameter (typically 43–45mm), generating continuous radial pressure and frictional resistance against the surrounding rock over the entire contact length.
Unlike resin-anchored or mechanical point-anchored rock bolts, the FB-47 provides immediate support upon installation — no curing time, no tensioning, no grout. This makes it the preferred choice in active mining environments where rapid ground support is critical and where rock conditions may shift between drilling and bolting.
1. Full-length C-shaped slot — compresses during insertion, creating continuous radial friction.
2. Tapered insertion end (38mm tip diameter) — guides the bolt into the hole without bending.
3. Welded ring flange — retains the bearing plate against the rock surface.
4. Compatible with dome plates, combi plates, mesh, and pull collars — integrates into complete ground support systems.
| Parameter | Minimum Value | Typical Value | Unit |
|---|---|---|---|
| Bolt Outer Diameter (A) | 47 | 47 | mm |
| Bolt Length (B) | 900 | 1,200–3,000 | mm |
| Taper End Diameter (C) | 38 | 38 | mm |
| Taper Slot Width (D) | 2 | 2 | mm |
| Taper Length (E) | 100 | 100 | mm |
| Yield Strength | 345 MPa / 120 kN | 445 MPa / 153 kN | MPa / kN |
| Ultimate Tensile Strength | 470 MPa / 160 kN | 530 MPa / 180 kN | MPa / kN |
| Typical Breaking Capacity | — | 178 kN | kN |
| Mass per Meter | — | 2.71 | kg/m |
| Cross-Sectional Area | — | 344 | mm² |
| Recommended Drill Bit Size | 41 | 43–45 | mm |
| Recommended Hole Diameter | 43 min | 43–45.5 max | mm |
| Standard Bolt Lengths | 450; 600–3,000mm in 300mm increments; non-standard available on request | mm | |
The performance of an 47mm Friction Stabilizer starts with the steel strip. TRM uses micro-alloyed high-strength steel with strict control over chemical composition — particularly low silicon (Si) and low phosphorus (P) levels. This matters for two reasons:
Mechanical performance: Low Si and P refine the grain structure, increasing yield strength and reducing brittleness. This prevents bending or kinking during high-speed jumbo installation.
Galvanizing quality: High Si and P cause excessive zinc-iron alloy layer growth during hot-dip galvanizing, leading to a dull, brittle, poorly-adhered coating. TRM's low-Si/P steel ensures a uniform, bright, and strongly bonded zinc layer.
TRM maintains a long-term cooperative relationship with our steel mill partner to secure consistent high-grade steel strip — a critical advantage over manufacturers who source steel on the spot market with variable quality.
Underground mines present highly corrosive environments — high humidity, acidic water, and constant exposure to moisture. An unprotected steel friction bolt can lose significant load-bearing capacity within 12–24 months due to corrosion. TRM addresses this with its self-owned hot-dip galvanizing production line — a rare advantage among friction bolt manufacturers.
| Coating Type | Corrosion Resistance | Service Life Extension | Recommended Environment |
|---|---|---|---|
| Black (Uncoated) | None | — | Dry mines, short-term temporary support |
| Hot-Dip Galvanized | High (50–85 µm zinc thickness) | 5–10+ years | Humid mines, acidic water, long-term permanent support |
| 3CR12 Stainless Steel | Very High | 15+ years | Highly corrosive environments, chemical exposure |
TRM's in-house galvanizing capability ensures consistent coating thickness, no transit damage between plating and packaging, and faster order turnaround — typically saving 5–7 days compared to manufacturers who outsource galvanizing.
Proper installation is as important as bolt quality. An incorrectly installed 47mm Split Set Stabilizer — driven too fast, into an oversized hole, or at an angle — will deliver only a fraction of its design anchorage.
Drill the hole. Use a 43–45mm button bit. Hole depth must be 150mm longer than bolt length to accommodate rock fretting during insertion.
Clean the hole. Flush drill cuttings completely. Residual debris reduces effective anchorage length.
Replace drill steel with driving dolly. Fit the dolly into the rock drill chuck (jumbo or stopper). Note: FB-47 requires jumbo/mechanized installation — not suitable for hand-held drills.
Slide the bearing plate onto the bolt. Dome plate, combi plate, or mesh plate — positioned against the ring flange.
Drive the bolt. Use full percussion and thrust. Keep the drill feed/thrust aligned with the hole axis (±10°). Driving the bolt at an angle will bend the tube and compromise ring weld integrity.
Stop when the plate is firmly seated. Over-driving damages the ring weld and reduces anchorage performance.
For a standard 2,400mm FB-47 bolt, the target drive time is 15–20 seconds using a modern jumbo drill. This drive time corresponds to optimal initial anchorage. Here is why drive time matters:
| Drive Time | Implication | Action Required |
|---|---|---|
| <10 seconds | Hole too large OR feed rate too high → weak anchorage | Check bit size for wear; reduce feed pressure |
| 15–20 seconds | Optimal — proper hole diameter and feed rate | Continue with standard procedure |
| >25 seconds | Hole too small (worn bit) → bolt may bend or kink | Replace drill bit; verify hole diameter |
Button bits are commonly 1.0–1.5mm larger than their stated nominal size. A new 43mm button bit may actually drill a 44.5mm hole. Always measure the actual hole diameter, not the bit label. TRM recommends a finished hole diameter of 43–45mm for optimal FB-47 performance. Using a 41mm bit (true hole ~42–42.5mm) provides the highest anchorage but requires careful feed control to avoid bolt damage.
| Hole Diameter | Anchorage Force | Assessment |
|---|---|---|
| 41mm | 10.5 tons | Maximum anchorage; requires precise installation |
| 42mm | 10.0 tons | Excellent; very tight fit |
| 43mm | 9.0 tons | Excellent; recommended lower bound |
| 44mm | 7.0 tons | Good; standard jumbo installation |
| 45mm | 4.0 tons | Marginal; upper acceptable limit |
| >45.5mm | Unacceptable | Hole oversized; replace bit and re-drill |
TRM manufactures three standard friction bolt diameters. Selecting the wrong model — using an FB-33 where an FB-47 is needed — results in inadequate ground support and safety risk. Here is the definitive comparison:
| Parameter | FB-33 | FB-39 | FB-47 |
|---|---|---|---|
| Bolt Diameter | 33mm | 39mm | 47mm |
| Hole Diameter Range | 30–32mm | 35–38mm | 43–45mm |
| Yield Strength | 87 kN | 94–100 kN | 120–153 kN |
| Tensile Strength | 99 kN | 107–115 kN | 160–180 kN |
| Mass per Meter | 1.64 kg/m | 1.77–1.84 kg/m | 2.71 kg/m |
| Installation Method | Hand-held stopper | Hand-held stopper / light jumbo | Jumbo / mechanized only |
| Typical Application | Light-duty mesh pinning, small tunnels | Medium-duty support, secondary reinforcement | Primary support, deep mines, high-stress rock |
| Pack Quantity per Pallet | 300 units | 150 units | 150 units |
When to specify FB-47: Deep underground mines (500m+ depth), high in-situ stress zones, permanent ground support in primary development headings, large-span excavations, and any application where FB-33 or FB-39 does not provide sufficient safety factor.
When FB-39 or FB-33 is sufficient: Shallow tunnels, secondary mesh pinning, temporary support in stable rock, hand-held installation scenarios where jumbo access is not available.
The pull test (also called a pull-out test or anchorage test) is the only way to verify that installed FB-47 Friction Bolts are delivering their design anchorage. TRM strongly recommends pull testing as a standard QA/QC procedure — typically testing 3% of installed bolts or a minimum of 3 bolts per 300 installed.
Hollow ram hydraulic jack — rated for 200+ kN capacity
Manual hydraulic pump with calibrated pressure gauge
Pull collar / pull ring — fitted onto the bolt before installation (TRM supplies purpose-made pull collars)
Displacement gauge (dial indicator) — measures bolt movement during loading
Load cell — for electronic data recording (optional, for detailed reporting)
Fit the pull collar onto the FB-47 bolt before installation. The pull collar sits behind the bearing plate and provides a gripping point for the hydraulic jack.
Install the bolt following the standard installation procedure (Section 5).
After installation (wait 0–30 minutes — friction bolts provide immediate anchorage, no curing time needed), position the hollow ram jack over the bolt and onto the pull collar.
Align the jack axis with the bolt axis (±5°). Eccentric loading will produce false-low results and may damage the equipment.
Apply load gradually at approximately 10 kN per minute. Record the load and corresponding displacement at 10 kN increments.
Stop the test when either: (a) the design anchorage load is reached (non-destructive test), or (b) the bolt exhibits continuous displacement without load increase (failure point, destructive test).
Record and report: peak load achieved, displacement at peak load, failure mode (if destructive), bolt ID, location, date, and operator.
For non-destructive QA/QC pull testing, the bolt should hold the design anchorage load (typically 8–10 tons for FB-47 in a 43–44mm hole) with minimal displacement (<5mm). If a bolt fails to reach 80% of design load, investigate the cause — most commonly oversized hole, insufficient drive, or fractured rock — and install a replacement bolt adjacent to the failed bolt (minimum 300mm spacing).
| Symptom | Likely Cause | Corrective Action |
|---|---|---|
| Low anchorage (<5 tons), bolt pulls out smoothly | Oversized hole (worn bit or wrong bit size) | Replace drill bit; verify bit diameter with caliper |
| Low anchorage, bolt pulls out with rock fragments | Weak/fractured rock; insufficient bolt length | Increase bolt length; consider supplementary cable bolts |
| Bolt ring weld fails before design load | Poor weld quality or over-driving during installation | Review installation procedure; check weld QC records |
| High displacement at low load, then holds | Hole cleaning incomplete; debris in hole bottom | Improve hole flushing procedure; drill 200mm deeper |
| Bolt bends/kinks during installation | Hole too small (worn bit); feed misaligned | Replace bit; check alignment (±10° max) |
The FB-47 Friction Bolt works as part of a complete ground support system. TRM manufactures a full range of compatible plates:
| Plate Type | Function | Best Application |
|---|---|---|
| Dome Plate | Standard bearing plate with domed profile; distributes load over rock surface | General primary support; most common configuration |
| Combi Plate | Combined dome + flat flange; larger footprint for weak rock | Soft or fractured rock; higher load distribution needed |
| Strata Plate | Heavy-duty thick plate for extreme load conditions | Deep mines, high-stress zones, squeezing ground |
| Mesh Plate | Large-area plate designed specifically for mesh retention | Mesh pinning; prevents mesh pull-through |
| Flat Plate | Compact flat plate for confined spaces | Low-profile applications; narrow vein mining |
| Pull Collar / Pull Ring | Fits behind plate for pull testing access | QA/QC testing; install on test-designated bolts |
10+ years specialized experience — TRM focuses exclusively on friction bolt and ground support manufacturing, not a general hardware factory.
30,000-ton annual capacity — consistent supply for large mining projects; urgent orders accommodated with rapid turnaround.
Self-owned galvanizing line — no outsourcing; full quality control over zinc coating thickness and adhesion.
PLC-controlled automated rollforming and welding — non-stop following-cut technology; auto-welding with self-checking; consistent product quality at scale.
Double-track QC system — on-site self-checking at each process stage + independent professional inspector sampling at each production stage.
Proven export track record — supplying major mining companies in Australia, South Africa, Russia, and Asian markets.
OEM and custom solutions — custom bolt lengths, plate designs, coatings, and packaging to match project specifications.
This guide directly addresses the technical specifications, installation procedures, and QA/QC requirements that mining engineers, contractors, and procurement teams need when specifying or purchasing FB-47 Friction Bolts.
All specifications reference current TRM production data and the latest Sandvik/Tanrimine FB-47 specification sheets. Installation guidelines reflect 2026 jumbo drill technology and best practices from operating mines in Australia and South Africa.
Tanrimine (TRM) is ISO9001 certified, operates a 30,000-ton annual capacity factory with self-owned galvanizing, and supplies major mining operations across Australia, South Africa, Russia, and Asia. Our products are manufactured on PLC-controlled automated rollforming and welding lines.
TRM products are trusted in safety-critical underground mining environments worldwide — including deep gold and copper mines in Australia — where bolt failure is not an option. Our double-track QC system ensures every bolt meets specification.
This guide is structured for rapid reference: specifications table first, installation procedure with step-by-step numbering, pull test acceptance criteria and failure mode diagnosis, and a product comparison table for FB-47/39/33 selection. Mining engineers can find critical data in under 60 seconds.
Tanrimine (TRM) is a professional FB-47 Friction Bolt manufacturer with 30,000-ton annual capacity, self-owned galvanizing, and ISO9001 quality management. We supply standard and custom-length FB-47 bolts with dome plates, combi plates, mesh plates, and pull collars — black or hot-dip galvanized. OEM and bulk orders welcome.
Request FB-47 Quote & Specifications →Email: jimwang@cnort.com | Web: www.miningfrictionbolt.com
