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PTO Torque Limiters

PTO Torque Limiters

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PTO Shaft Torque Limiters for Agricultural Machinery

A PTO torque limiter is a critical safety and protection device installed on the PTO driveline shaft between the tractor and the implement. Its primary function is to disconnect or slip when the transmitted torque exceeds a pre-set threshold, thereby preventing catastrophic damage to the gearbox, driveshaft, universal joints, and the implement itself. In the demanding agricultural conditions across Australia, sudden obstructions such as rocks, stumps, or tangled crop material can cause instantaneous torque spikes that would otherwise shear gears or snap shafts without a properly rated torque limiter in place.

As a trusted PTO shaft and driveline components supplier in Australia, we offer a comprehensive range of PTO torque limiters including shear bolt types, ratchet types, automatic (cam) types, and friction types. Each design addresses specific operational demands, from light-duty seeding and spraying equipment to heavy-duty rotary tillers, balers, and forage harvesters. All our torque limiters feature 1 3/8" Z6 or 1 3/8" Z21 or 1 3/4" Z6 or 1 3/4" Z20 spline connections, ensuring compatibility with standard tractor PTO output shafts used throughout the Australian market.

Choosing the correct torque limiter type and torque rating is essential to safeguarding your entire driveline investment. Below you will find detailed specifications for every series we supply, along with guidance to help you select the ideal unit for your application. You can also explore our full selection of agricultural gearboxes that work in conjunction with PTO torque limiters to deliver optimised power transmission.

Types of PTO Torque Limiters

We supply four main categories of torque limiters, each engineered for distinct operating conditions and implement requirements.

Shear Bolt Torque Limiter

Uses sacrificial shear bolts that break at a calibrated torque threshold. Low cost and simple to reset by replacing the bolt. Ideal for applications where overloads are rare but severe. Torque range: 570 - 4500 Nm.

Ratchet Torque Limiter

Employs spring-loaded pawl kits that ratchet when torque exceeds the setting, then automatically re-engage. No replacement parts needed after slip events. Setting torque range: 400 - 2000 Nm.

Automatic Torque Limiter

Features cam-actuated spring packs that automatically disengage and re-engage the driveline. Provides smooth, repeatable protection for continuous-duty implements. Torque range: 1600 - 4500 Nm.

Friction Torque Limiter

Utilizes friction disc packs compressed by spring bolts to provide progressive slip under overload. Adjustable torque settings and smooth engagement. Torque range: 800 - 4500 Nm. Widest selection available.

PTO Torque Limiters for Sale

Browse our complete range of PTO torque limiters available for purchase in Australia. Click on any product to view full specifications, pricing, and ordering options.

PTO Torque Limiter Specifications

Select a torque limiter type below to view detailed series data, dimensions, spline configurations, and component breakdowns.

Shear Bolt
Ratchet
Automatic
Friction

Shear Bolt Torque Limiter Series

Shear bolt torque limiters provide the simplest and most cost-effective overload protection. When the driveline torque exceeds the shear bolt's rated capacity, the bolt fractures cleanly, immediately disconnecting the drive. After clearing the obstruction, a new shear bolt is installed and the driveline is back in operation within minutes. These units are composed of a yoke, hub, steel ball, push pin, grease nipple, and shear bolt with nut.

SB Series (Standard Spline Hub)

SeriesTorque (Nm)SplineA (mm)B (mm)C (mm)D (mm)
1SB5701 3/8" Z6952035M6x40
1SBT174045M6x40
2SB740982145M6x40
2SBT179048M6x40
3SB111010238M8x45
3SBT1120040M8x45
4SB140010748M8x50
4SBT1160055M8x50
5SB160011455M8x45
5SBT1210046M10x50
6SB17501372160M8x55
6SBT1250055M10x55
32SB16001142455M8x45
32SBT1210046M10x50
7SB205015245M10x60
7SBT1320049M12x65

SB Series (Large Spline Hub)

SeriesTorque (Nm)SplineA (mm)B (mm)C (mm)D (mm)
7NSB23001 3/8" Z61392450M10x65
7NSBT1300060M10x65
8SB27001 3/8" Z615257M12x65
8SBT1350060M12x65
8SB.C27001 3/4" Z615257M10x65
8SBT1.C350060M12x65
38SB27001 3/8" Z615257M12x65
9SB35001 3/8" Z660M12x65
9SBT140001 3/8" Z615257M12x65
9SB.C35001 3/4" Z660M12x65
9SBT1.C40001 3/4" Z657M12x65
10SB35001 3/8" Z615249M14x70
10SBT145001 3/8" Z657M12x65
10SB.C35001 3/4" Z649M14x70
10SBT1.C45001 3/4" Z657M12x65
36SB24001 3/8" Z613753M10x65
36SBT132001 3/8" Z649M10x65
42SB35001 3/8" Z615257M12x65
42SBT140001 3/8" Z660M12x65
42SB.C35001 3/4" Z657M12x65
42SBT1.C40001 3/4" Z660M12x65

Shear Bolt Torque Limiter Components

No.DescriptionNotes
1Yoke-
2Grease nipple-
3Steel ball-
4Hub-
5Push pinQty.=2 (large series)
6Shear bolt & Nut-

Ratchet Torque Limiter Series

Ratchet torque limiters use spring-loaded pawl kits that disengage at the set torque, producing an audible clicking sound to alert the operator. Once the overload condition is removed, the pawls automatically re-engage and the driveline resumes normal operation. No replacement parts are required after a slip event, making ratchet limiters ideal for applications where frequent moderate overloads occur. Components include circlip, retaining washer, dust guard ring, push pin kit, hub, pawl kit, housing with yoke, and grease nipple.

SA1 Series (Setting Torque: 400 Nm)

SeriesSetting Torque (Nm)SplineA (mm)B (mm)
1SA14001 3/8" Z613821
2SA1138
3SA1149
4SA1150

SA1 with Splined Shaft (SAS1)

SeriesSetting Torque (Nm)Spline (female)Spline (male)A (mm)B (mm)C (mm)
SAS14001 3/8" Z61 3/8" Z61442138

SA2 Series (Setting Torque: 800 Nm)

SeriesSetting Torque (Nm)SplineA (mm)B (mm)
1SA28001 3/8" Z615621
2SA2156
3SA2167
4SA2168
5SA2172
6SA2178
7SA2189
7NSA2175

SA3 Series (Setting Torque: 1200 Nm)

SeriesSetting Torque (Nm)SplineA (mm)B (mm)
2SA312001 3/8" Z617122
3SA3182
4SA3183
5SA3187
6SA3193
7SA3204
7NSA3190

SA4 & SA5 Series (Setting Torque: 1600 - 2000 Nm)

SeriesSetting Torque (Nm)SplineA (mm)B (mm)
5SA416001 3/8" Z620622
6SA4212
6SA520001 3/8" Z623122

Ratchet Torque Limiter with Splined Shaft

SeriesSetting Torque (Nm)Spline (female)Spline (male)A (mm)B (mm)C (mm)
SAS28001 3/8" Z61 3/8" Z61612138
SAS312001 3/8" Z61 3/8" Z6164.52238
SAS416001 3/8" Z61 3/8" Z61862238
SAS520001 3/8" Z61 3/8" Z62052238

Ratchet Torque Limiter Components

No.DescriptionNotes
1Circlip-
2Retaining washer-
3Dust guard ring-
4Push pin kit-
5Hub-
6Pawl kitQty.=8 to 40 depending on series
7Housing with yoke-
8Grease nipple-

Automatic Torque Limiter Series

Automatic torque limiters (also known as cam-type torque limiters) provide highly reliable, repeatable overload protection for heavy-duty implements. They feature a cam-actuated mechanism with spring packs that automatically disengage the driveline when the torque exceeds the set value, and smoothly re-engage once the overload condition subsides. Components include outer housing with yoke, bushing, spring pack, hub with taper pin and bushings, sealing ring, O-ring, locking plate, snap ring, cam, and taper pin.

SC Series (Yoke Hub, 152mm Disc)

SeriesTorque (Nm)SplineA (mm)B (mm)C (mm)
4SC151 / 4SC151.D16001 3/8" Z6 / Z21207.528152
5SC151 / 5SC151.D21001 3/8" Z6 / Z21207.5
6SC151 / 6SC151.D26001 3/8" Z6 / Z21213
6SC151.C / 6SC151.E21001 3/4" Z6 / Z20
7NSC151 / 7NSC151.D28001 3/8" Z6 / Z21
7NSC151.C / 7NSC151.E26001 3/4" Z6 / Z20213152
8SC151 / 8SC151.D28001 3/8" Z6 / Z21220152
8SC151.C / 8SC151.E26001 3/4" Z6 / Z20220
36SC151 / 36SC151.D28001 3/8" Z6 / Z21213
36SC151.C / 36SC151.E26001 3/4" Z6 / Z20213

SC176 Series (176mm Disc)

SeriesTorque (Nm)SplineA (mm)B (mm)C (mm)
8SC176 / 8SC176.D3000 / 35001 3/8" Z6 / Z2122428176
8SC176.C / 8SC176.E3500 / 40001 3/4" Z6 / Z20233
9SC176 / 9SC176.D4000 / 45001 3/8" Z6 / Z21233
9SC176.C / 9SC176.E45001 3/4" Z6 / Z20233

SCF Series (Flanged Housing)

SeriesTorque (Nm)SplineA (mm)B (mm)C (mm)
SCF151 / SCF151.D1600 / 21001 3/8" Z6 / Z2117129168
SCF151.C / SCF151.E2600 / 28001 3/4" Z6 / Z20
SCF176 / SCF176.D3000 / 35001 3/8" Z6 / Z2117528176
SCF176.C / SCF176.E4000 / 45001 3/4" Z6 / Z20

Automatic Torque Limiter Components

No.DescriptionNotes
1Outer housing + yoke / flange-
2Bushing-
3Spring pack-
4Hub with taper pin and bushings-
5Bushing-
6Sealing ring-
7O-ring-
8Locking plate-
9Snap ring-
10BushingQty.=4
11CamQty.=4
12Taper pinWith nuts

Friction Torque Limiter Series

Friction torque limiters offer the widest range of torque settings and the smoothest overload protection. They use friction disc packs compressed by spring-loaded bolts to transmit torque. When the overload threshold is reached, the discs begin to slip progressively, dissipating the excess energy as heat rather than transmitting destructive shock loads. The torque setting can be fine-tuned by adjusting the spring bolt tension. We offer multiple sub-types: FF (standard yoke), FFV (standard yoke with intermediate hub), FFS/FFVS (flanged spline), FFT/FFVT (Belleville spring), FFST/FFSVT (flanged spline with Belleville spring), and FCS (compact flanged).

FF Series - Standard Friction Torque Limiter

SeriesMax Torque (Nm)Friction DiscSplineA (mm)B (mm)C (mm)
4FF0 / 5FF0800 / 1000120mm1 3/8" Z6135 / 13729160
4FF1 / 5FF1 / 6FF11200140mm1 3/8" Z6 / Z21150 / 152 / 16029180
4FF2 / 5FF2 / 6FF21500160mm1 3/8" Z6 / Z21150 / 152 / 16429200
7FF2 / 7NFF2 / 8FF21800160mm1 3/8" Z6 / Z21 / 1 3/4" Z6 / Z20169 / 164 / 16929200
5FF3 / 6FF32000140mm1 3/8" Z6 / Z21168 / 17629180
5FF4 - 10FF42000 - 3000160mm1 3/8" Z6 / Z21 / 1 3/4" Z6 / Z20168 - 19029200
42FF42800160mm1 3/8" Z6 / Z21 / 1 3/4" Z6 / Z2019029200

FFV Series - Friction Limiter with Intermediate Hub

SeriesMax Torque (Nm)Friction DiscSplineA (mm)B (mm)C (mm)
4FFV1 / 5FFV1 / 6FFV11200 / 900140mm1 3/8" Z6 / Z21150 / 152 / 16030.5180
4FFV2 - 8FFV21200 - 1800160mm1 3/8" Z6 / Z21 / 1 3/4" Z6 / Z20143 - 16826 / 30.5200
5FFV3 / 6FFV32000140mm1 3/8" Z6 / Z21160 / 16830.5180
5FFV4 - 10FFV42000 - 2800160mm1 3/8" Z6 / Z21 / 1 3/4" Z6 / Z20160 - 18930.5200
42FFV42800160mm1 3/8" Z6 / Z21 / 1 3/4" Z6 / Z20182 / 18930.5200

FFS / FFVS Series - Flanged Spline Friction Limiter

SeriesMax Torque (Nm)Friction DiscSpline (female)Spline (male)A (mm)B (mm)C (mm)D (mm)
FFS1 / FFS1D1200140mm1 3/8" Z6 / Z211 3/8" Z6161.52938180
FFS2 / FFS2D / FFS2C / FFS2E1800160mm1 3/8" Z6 / Z21 / 1 3/8" Z6 / Z201 3/8" Z6161.52938200
FFS3 / FFS3D1500140mm1 3/8" Z6 / Z211 3/8" Z61772938180
FFS4 / FFS4D / FFS4C / FFS4E2500160mm1 3/8" Z6 / Z21 / 1 3/8" Z6 / Z201 3/8" Z61772938200
FFVS1 / FFVS1D1200 / 900140mm1 3/8" Z6 / Z211 3/8" Z6161.52938180
FFVS2 / FFVS2D / FFVS2C / FFVS2E1800160mm1 3/8" Z6 / Z21 / 1 3/8" Z6 / Z201 3/8" Z6161.52938200
FFVS3 / FFVS3D2000140mm1 3/8" Z6 / Z211 3/8" Z61772938180
FFVS4 / FFVS4D / FFVS4C / FFVS4E2500160mm1 3/8" Z6 / Z21 / 1 3/8" Z6 / Z201 3/8" Z61772938200

FFT / FFVT Series - Belleville Spring Friction Limiter

SeriesMax Torque (Nm)Friction DiscSplineA (mm)B (mm)C (mm)
4FFT0 / 5FFT0800120mm1 3/8" Z6150 / 15229160
4FFT1 - 6FFT1900140mm1 3/8" Z6 / Z21150 - 16029180
5FFT2 - 8FFT21200160mm1 3/8" Z6 / Z21 / 1 3/4" Z6 / Z20152 - 16929200
6FFT4 - 8FFT41600 - 2000160mm1 3/8" Z6 / Z21 / 1 3/4" Z6 / Z20172 - 18430.5200
4FFVT1 - 6FFVT1900 - 1200140mm1 3/8" Z6 / Z21150 - 16029180
4FFVT2 - 8FFVT21200160mm1 3/8" Z6 / Z21 / 1 3/4" Z6 / Z20143 - 16829200
6FFVT4 - 8FFVT41600 - 2000160mm1 3/8" Z6 / Z21 / 1 3/4" Z6 / Z20175 - 18229200

FCS Series - Compact Flanged Friction Limiter

SeriesFriction DiscDisc QtyMax Torque (Nm)Spline (female)Spline (male)A (mm)B (mm)C (mm)D (mm)
FCS165 / FCS165D125mm28001 3/8" Z6 / Z211 3/8" Z61402035165
FCS203 / FCS203D163mm215001 3/8" Z6 / Z211 3/8" Z6155.53035203

Friction Torque Limiter Components (Standard FF/FFV)

No.DescriptionNotes
1Pressure plate-
2Internal discQty.=2
3Friction liningQty.=2 to 4
4Hub-
5Taper pin for hubWith nuts
6Bushing-
7Flanged yoke-
8Complete bolt & SpringQty.=8

How to Choose the Right PTO Torque Limiter

Selecting the correct torque limiter involves matching several key parameters to your specific implement and working conditions.

1

Determine Torque Rating

Calculate the maximum torque your implement can generate during normal operation and overload events. The limiter's rated torque should be set slightly above the normal operating torque but below the damage threshold of your driveline components.

2

Identify Spline Configuration

Match the spline type to your tractor PTO output shaft. Common configurations include 1 3/8" x 6 spline (540 rpm) and 1 3/8" x 21 spline or 1 3/4" x 20 spline (1000 rpm). The limiter must mate perfectly with both the tractor PTO and the implement input shaft.

3

Choose Limiter Type

Select based on overload frequency: shear bolt for rare/severe overloads, ratchet for frequent moderate loads, friction for continuous slip protection, and automatic for heavy-duty implements requiring repeatable precision.

4

Check Physical Dimensions

Verify that the torque limiter's overall length (A dimension), hub diameter (B dimension), and outer housing diameter (C/D dimension) will physically fit within the available space between your tractor and implement.

Common Applications for PTO Torque Limiters

PTO torque limiters protect a wide variety of agricultural machinery. Below are the most common implement categories and the recommended torque limiter types.

Rotary Tillers & Cultivators

Frequent encounters with rocks and roots demand friction or automatic torque limiters with ratings of 1500 - 3000 Nm. The progressive slip of friction types absorbs repeated shocks without requiring reset.

Hay Balers & Forage Harvesters

High-inertia loads and occasional crop jamming require robust protection. Automatic torque limiters (SC176 series, 3000 - 4500 Nm) provide instant disengagement and automatic re-engagement.

Mowers & Slashers

Hidden obstacles make shear bolt or friction limiters essential. Shear bolt types (SB series, 1100 - 2500 Nm) offer a simple, cost-effective solution for occasional impacts.

Seeders & Planters

Lower torque requirements (400 - 800 Nm) suit ratchet torque limiters from the SA1 and SA2 series. The automatic re-engagement ensures uninterrupted seeding operations.

Manure Spreaders & Sprayers

Moderate torque demands with occasional blockages. Ratchet limiters (SA2/SA3 series, 800 - 1200 Nm) provide reliable protection with no downtime for part replacement.

PTO Generators & Water Pumps

Steady-state loads require smooth torque transfer. Friction torque limiters with Belleville springs (FFT series) deliver consistent, vibration-free torque limiting for stationary PTO-driven equipment.

Frequently Asked Questions

Get answers to the most common questions about PTO torque limiters for agricultural driveline systems.

What is the difference between a shear bolt and a friction torque limiter?

A shear bolt torque limiter uses a sacrificial bolt that fractures at a precise torque level, completely disconnecting the driveline until the bolt is replaced. A friction torque limiter uses disc packs that slip progressively under overload and automatically re-engage once the overload subsides. Shear bolt types are lower cost but require manual replacement after each event, while friction types are better suited for applications with frequent overloads.

How do I determine the correct torque setting for my implement?

The torque limiter setting should be approximately 1.5 to 2 times the normal operating torque of the implement. Consult your implement manufacturer's specifications for the maximum input torque rating. The limiter must be set below the weakest component's failure threshold in the driveline but above the normal peak operating torque to avoid nuisance tripping.

Can I use a 1 3/4" Z6 spline limiter on a 540 rpm PTO?

The standard 540 rpm PTO shaft uses a 1 3/8" x 6 spline (Z6) configuration. A 1 3/4" Z6 spline is typically associated with 1000 rpm PTO applications. Using mismatched splines will not physically connect. Always verify the spline configuration of both your tractor PTO output and implement input shaft before ordering.

How often should I inspect or service my PTO torque limiter?

Inspect the torque limiter before each use season or every 50 hours of operation. Check for worn friction discs (friction types), damaged pawl kits (ratchet types), or cracked housing. Grease all nipple points at the interval specified by the manufacturer. For friction types, verify that the spring bolt tension has not changed, as this directly affects the torque setting.

What is an overrunning clutch and how does it relate to torque limiters?

An overrunning clutch (also called a freewheel clutch) allows the implement to continue rotating freely when the tractor PTO is disengaged, preventing the implement's inertia from back-driving the tractor. It serves a different purpose from a torque limiter but is often used in combination with one. Our RA1 and RA2 series overrunning clutches can be paired with any of our torque limiter types for complete driveline protection. Explore our full PTO shaft product range for compatible overrunning clutch options.

Do you supply torque limiters with both female and male spline connections?

Yes. Our standard torque limiter series feature a female spline hub that slides onto the tractor PTO output shaft. We also offer models with splined shaft output (SAS series for ratchet types, FFS/FFVS series for friction types) that include both a female spline input and a male spline output, providing a pass-through connection without an additional coupling.

Need Help Selecting the Right Torque Limiter?

Our technical team in Australia can help you match the correct torque limiter type, series, and torque rating to your specific tractor and implement combination. Contact us today for expert advice and competitive pricing.

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