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Shear Bolt Torque Limiter for PTO Shaft | Agricultural Overload Safety Clutch
The Shear Bolt Torque Limiter — also known as a shear pin clutch, PTO overload protector, or bolt-type safety coupling — is a proven mechanical safeguard engineered specifically for agricultural PTO drive lines. When torque spikes beyond a preset threshold, a sacrificial shear bolt fractures instantly, disconnecting the driven implement from the tractor’s power take-off and preventing catastrophic damage to gearboxes, universal joints, and other costly driveline components. Trusted by farmers and implement dealers across the globe, this device delivers dependable protection for rotary cutters, hay balers, manure spreaders, and dozens of other PTO-driven machines.
Technical Specifications
| Serie | Torque (Nm) | Spline | A (mm) | B (mm) | C (mm) | D (mm) |
|---|---|---|---|---|---|---|
| 1SB | 570 | 1 3/8"Z6 | 95 | 20 | 35 | M6×40 |
| 1SBT1 | 740 | 45 | ||||
| 2SB | 740 | 98 | 21 | 45 | M6×40 | |
| 2SBT1 | 790 | 48 | ||||
| 3SB | 1110 | 102 | 38 | M8×45 | ||
| 3SBT1 | 1200 | 40 | ||||
| 4SB | 1400 | 107 | 48 | M8×50 | ||
| 4SBT1 | 1600 | 55 | ||||
| 5SB | 1600 | 114 | 55 | M8×45 | ||
| 5SBT1 | 2100 | 46 | M10×50 | |||
| 6SB | 1750 | 137 | 60 | M8×55 | ||
| 6SBT1 | 2500 | 55 | M10×55 | |||
| 32SB | 1600 | 114 | 55 | M8×45 | ||
| 32SBT1 | 2100 | 46 | M10×50 | |||
| 7SB | 2050 | 1 3/8"Z6 | 152 | 24 | 45 | M10×60 |
| 7SBT1 | 3200 | 49 | M12×65 |
| Serie | Torque (Nm) | Spline | A (mm) | B (mm) | C (mm) | D (mm) |
|---|---|---|---|---|---|---|
| 7NSB | 2300 | 1 3/8"Z6 | 139 | 24 | 50 | M10×65 |
| 7NSBT1 | 3000 | 60 | M12×65 | |||
| 8SB | 2700 | 1 3/8"Z6 | 152 | 46 | M12×65 | |
| 8SBT1 | 3500 | 57 | M12×65 | |||
| 8SB.C | 2700 | 1 3/4"Z6 | 152 | 57 | M12×65 | |
| 8SBT1.C | 3500 | 60 | M10×65 | |||
| 38SB | 2700 | 1 3/8"Z6 | 152 | 57 | M12×65 | |
| 9SB | 3500 | 1 3/8"Z6 | 60 | M12×65 | ||
| 9SBT1 | 4000 | 1 3/8"Z6 | 152 | 57 | M12×65 | |
| 9SB.C | 3500 | 1 3/4"Z6 | 57 | M12×65 | ||
| 9SBT1.C | 4000 | 1 3/4"Z6 | 60 | M12×65 | ||
| 10SB | 3500 | 1 3/8"Z6 | 152 | 49 | M14×70 | |
| 10SBT1 | 4500 | 1 3/8"Z6 | 60 | M12×65 | ||
| 10SB.C | 3500 | 1 3/4"Z6 | 57 | M12×65 | ||
| 10SBT1.C | 4500 | 1 3/4"Z6 | 49 | M14×70 | ||
| 36SB | 2400 | 1 3/8"Z6 | 137 | 53 | M10×65 | |
| 36SBT1 | 3200 | 1 3/8"Z6 | 137 | 49 | M10×65 | |
| 42SB | 3500 | 1 3/8"Z6 | 152 | 57 | M12×65 | |
| 42SBT1 | 4000 | 1 3/8"Z6 | 60 | M12×65 | ||
| 42SB.C | 3500 | 1 3/4"Z6 | 57 | M12×65 | ||
| 42SBT1.C | 4000 | 1 3/4"Z6 | 60 | M12×65 |
Component parts: Yoke, Grease nipple, Steel ball, Hub, Push pin, Shear bolt & Nut.
Key Features & Advantages
Shear bolt fractures within milliseconds of a torque spike, cutting the drive connection immediately and shielding downstream equipment.
Only the inexpensive shear bolt needs replacing after activation — no costly clutch packs, springs, or friction discs required.
Replacement bolts can be swapped in minutes with basic hand tools, minimizing field downtime during critical harvest windows.
Available from 570 Nm to 4500 Nm, covering virtually every agricultural PTO application from light-duty to heavy-duty.
Precision-machined hubs and heat-treated yokes deliver reliable performance across seasons of continuous use.
Standard 1 3/8" Z6 and 1 3/4" Z6 spline options fit most North American, European, and Australian PTO systems.
How It Works
The shear bolt torque limiter operates on a straightforward mechanical principle. A calibrated steel bolt passes through aligned holes in the hub and the yoke housing, locking the two components together. Under normal operating conditions the bolt transmits rotational force from the tractor PTO to the implement. When an obstruction — such as a rock, fence post, or seized bearing — causes the driven torque to exceed the bolt’s shear strength, the bolt fractures cleanly at a pre-engineered groove, instantly decoupling input and output sides. The tractor PTO continues to spin freely while the implement stops, preventing damage to gearboxes, cross joints, and the implement itself. After the obstruction is cleared, a new shear bolt is inserted, and the machine is ready to resume work.
Typical Application Scenarios
Protects cutter gearboxes when blades strike rocks, stumps, or hidden objects in pasture land.
Prevents drive train failures caused by foreign objects or overfeeding of crop material.
Shields the beater mechanism from jams created by frozen manure or foreign debris.
Disconnects drive instantly if the auger hits solid rock or compacted clay, protecting both the auger and the tractor gearbox.
Torque Limiter Type Comparison
| Feature | Ball Detent | Friction Disc | Shear Pin/Bolt | Ratchet |
|---|---|---|---|---|
| Torque Range | 570 – 3200 Nm | 800 – 3000 Nm | 570 – 4500 Nm | 400 – 2000 Nm |
| Speed Range | 540/1000 RPM | 540/1000 RPM | 540/1000 RPM | 540/1000 RPM |
| Reset Method | Automatic | Automatic (slip) | Manual (bolt change) | Automatic |
| Best Application | Moderate shock loads | Continuous slip protection | Extreme overload protection | One-direction protection |
Installation & Usage Guide
- Confirm the spline size (1 3/8" Z6 or 1 3/4" Z6) matches your PTO shaft.
- Slide the limiter hub onto the PTO profile tube until the bolt holes align.
- Insert the shear bolt and torque the nut to the specified value — do not over-tighten.
- Connect the yoke end to the implement’s input shaft using the push pin.
- Apply grease through the nipple before first use and at every 8 operating hours.
- Keep spare shear bolts in the tractor toolbox for rapid field replacement.
Safety Notice: Always shut down the PTO and switch off the engine before replacing a shear bolt. Wear appropriate PPE including gloves and safety glasses.
Selection Guide
Choosing the right shear bolt torque limiter requires matching several critical parameters to your specific application. First, determine the maximum operating torque of your implement — this information is typically found in the implement manual or can be calculated from PTO horsepower and RPM. Select a limiter whose rated shear torque sits 20–30 % above the implement’s normal operating torque to avoid nuisance shearing while still providing meaningful protection. Verify the spline profile (1 3/8" Z6 is the most common worldwide; 1 3/4" Z6 is used on heavier implements). Check the dimensional envelope (A, B, C, D dimensions) to ensure the limiter fits within the available space between tractor and implement. For implements prone to frequent shock loads (e.g., stump grinders, rock pickers), consider pairing a shear bolt limiter with a friction-type clutch for dual-layer protection.
Quality Certifications & Service
All shear bolt torque limiters are manufactured under an ISO 9001:2015 certified quality management system. Products carry CE marking for compliance with European machinery safety directives and meet ASABE S205.2 dimensional standards for North American PTO applications. Every batch undergoes destructive shear testing, dimensional inspection, and hardness verification prior to shipment. We stand behind our products with a 12-month warranty covering defects in materials and workmanship, complemented by responsive technical support and worldwide spare parts availability.
Veelgestelde vragen
How do I determine the correct shear bolt grade for my implement?
Refer to the implement manufacturer’s specified PTO torque requirement. Choose a limiter series whose rated torque is 20–30 % higher than the implement’s peak operating torque to avoid premature shearing during normal start-up surges.
Can I substitute a higher-strength bolt to increase the trip torque?
Never substitute non-standard bolts. Using a harder bolt raises the trip point beyond design limits and may transfer destructive forces to the gearbox or cross joints, voiding both the limiter and implement warranties.
How often should I grease the shear bolt torque limiter?
Apply a full stroke of lithium-based EP grease through the nipple every 8 hours of operation, or at least once before each seasonal start-up. Adequate lubrication extends bearing and spline life substantially.
Is this compatible with 540 RPM and 1000 RPM PTO systems?
Yes. The shear bolt limiter is a purely mechanical device that functions regardless of rotational speed. However, ensure the torque rating is matched correctly because higher-RPM systems deliver different torque profiles at the same horsepower.
What is the typical lifespan of a shear bolt limiter housing?
With proper greasing and correct bolt selection, the housing and hub assembly can last 10+ years. Only the sacrificial shear bolt requires periodic replacement after an overload event.
Customer Testimonials
“Running a 7SBT1 on our hay baler across 2,000 acres. Already saved the gearbox twice this season when we hit hidden fence wire. Bolts are cheap and swap in two minutes.”
“We put the 6SBT1 on every rotary cutter in our fleet. In rocky cerrado soils, shear protection is not optional — it is survival gear for the driveline.”
“Precision-manufactured and reliable. The 3SB fits our Krone mower perfectly and trips at exactly the right torque every time.”
“I’ve been farming for 30 years and these shear bolts are the best insurance policy for my PTO shafts. Simple, effective, and no surprises.”
“Excellent rapport qualité-prix. The 5SBT1 protects our manure spreader reliably through every winter season.”
Related Products & Accessories
We supply a full range of PTO driveline components alongside torque limiters. Explore our complete PTO shaft assemblies in G, L, S, and T series, as well as individual accessories including yokes (plain bore, splined, quick-release), PTO safety shields & guards, cross journals & bearing kits, slip-joint profiles, adapters & couplers, and landbouwversnellingsbakken for right-angle drives. Whether you need a single replacement limiter or a complete OEM driveline solution, our engineering team can assist with specification and customization.
Partner With Us
Looking for a dependable torque limiter supplier for your farm equipment brand, implement dealership, or aftermarket distribution network? We offer competitive OEM & wholesale pricing, custom torque ratings, private labeling, and global logistics support. Contact our sales team today to request a quotation or discuss your technical requirements. Let’s build a stronger driveline together.
