What does the 45 HP rating mean on this rotary cutter gearbox?

The 45 HP rating is the maximum continuous input power the gearbox is designed to transmit without exceeding its thermal and mechanical limits. It is intended for tractors with PTO output up to 45 HP driving a 4', 5' or 6' rotary cutter. Running the gearbox above 45 HP sustained will accelerate gear and bearing wear and is not covered by the standard warranty.

Which rotary cutter sizes does this gearbox fit?

The gearbox fits most 4', 5' and some 6' rotary cutters from common brands. The key compatibility checks are: (1) the 1-3/8" smooth input shaft with shear bolt hole matches the PTO shaft yoke, (2) the 1-1/2" 12-spline output shaft matches the blade carrier hub, and (3) the mounting bolt pattern matches the mower deck (4-3/4" center-to-center with 5/8" bolts, or the 6-1/2" alternate pattern). If all three match, the gearbox is a direct replacement.

How do I identify the gearbox I need to replace?

Measure these four dimensions on the existing gearbox: (1) input shaft diameter and length, (2) output shaft diameter and spline count, (3) mounting bolt hole center-to-center distance, and (4) overall gearbox height. Compare these to the specifications on this page. If the original gearbox has a nameplate or casting number, send a photo for a direct cross-reference. Raydafon can confirm the match before shipping.

Can I buy just the input shaft or output shaft?

No. The input shaft and output shaft are precision-matched gear pairs and must be replaced as a set. A used input gear paired with a new output gear will have mismatched wear patterns that cause noise, vibration and premature failure. Raydafon supplies the shaft kit as four matched components: input shaft, input gear, output shaft and output gear.

What oil does the rotary cutter gearbox use and how often should it be changed?

The gearbox uses a gear oil bath, typically SAE 80W-90 or EP-90 gear oil depending on ambient conditions. Change the oil after the first 50 hours of operation for a new or rebuilt gearbox, then every 500 hours or annually under normal use. For heavy-duty use or dusty conditions, change every 250 hours. Check the oil level at the fill plug before each season.

How much does the gearbox weigh and how is it shipped?

The gearbox weighs 47 lbs (21.3 kg). It ships in a foam-lined carton sized for the gearbox and shaft kit. For single-unit orders, express couriers such as DHL, FedEx and UPS are available. For wholesale orders of 10 units or more, consolidated air freight or sea freight reduces the per-unit shipping cost significantly.

Does Raydafon offer OEM or private label for the rotary cutter gearbox?

Yes. Raydafon supplies OEM quantities with custom ratios, input shaft lengths, output spline counts and mounting bolt patterns matched to the customer's mower deck. Private-label casting marks and packaging are available for wholesale orders. Send the required ratio, shaft dimensions, bolt pattern and quantity for a quotation. Minimum order quantity for custom castings depends on the pattern complexity.

What is the lead time and MOQ for the 45 HP Rotary Cutter Gearbox?

Standard configuration ships in 15-30 days. MOQ is 1 unit for the standard gearbox and shaft kit. Custom ratios and mounting patterns are confirmed with the quotation. Raydafon is based in Ningbo, China and ships worldwide. Payment terms, shipping method and Incoterms are confirmed at order.

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Rotary Cutter Gearbox

45 HP Rotary Cutter Gearbox is a shear-pin replacement gearbox for 4', 5' and some 6' rotary cutters. It uses a 1-3/8" smooth input shaft with 1/2" shear bolt hole, a 1:1.47 single-stage reduction ratio, and a 1-1/2" 12-spline output shaft that drives the blade carrier. The cast iron housing weighs 47 lbs and mounts on a 4-3/4" center-to-center bolt pattern with 5/8" bolts. A 1" castle nut and cotter pin secure the blade pan. Input and output shafts are supplied as a matched four-piece kit (input shaft, input gear, output shaft, output gear). Compatible with most 4', 5' and 6' rotary cutter brands. OEM and wholesale quantities available from Raydafon's Ningbo factory.

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Product Description

Raydafon · Shear-Pin Rotary Cutter Gearbox · 45 HP · 1:1.47

45 HP Rotary Cutter Gearbox — 1:1.47 Shear Pin Input, 1-1/2" 12-Spline Output for 4', 5' and 6' Cutters

The 45 HP Rotary Cutter Gearbox is a shear-pin replacement gearbox built for 4', 5' and some 6' rotary cutters. It uses a 1-3/8" smooth input shaft with a 1/2" shear bolt hole — the shear pin protects the gear train if the blade strikes a stump or rock. The 1:1.47 single-stage reduction drives a 1-1/2" 12-spline output shaft that mounts the blade carrier.

The cast iron housing weighs 47 lbs and mounts on a 4-3/4" center-to-center bolt pattern with four 5/8" bolts. A 1" castle nut and cotter pin (nut included) secure the blade pan to the output shaft. The gearbox is supplied with a matched four-piece shaft kit — input shaft, input gear, output shaft and output gear — because mixing a new gear with a worn one causes noise and premature failure.

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Rated Power45 HP

Reduction Ratio1:1.47

Input Shaft1-3/8" Smooth

Shear Bolt1/2" Hole

Output Shaft1-1/2" 12-Spline

Bolt Pattern4-3/4" Centers

Weight47 lbs

Blade Fastener1" Castle Nut

Direct answer The 45 HP Rotary Cutter Gearbox is a shear-pin replacement gearbox for 4', 5' and some 6' rotary cutters. It uses a 1-3/8" smooth input shaft with a 1/2" shear bolt hole, a 1:1.47 single-stage reduction ratio, and a 1-1/2" 12-spline output shaft that drives the blade carrier. The cast iron housing weighs 47 lbs and mounts on a 4-3/4" center-to-center bolt pattern with 5/8" bolts. A 1" castle nut and cotter pin secure the blade pan. The input and output shafts are supplied as a matched four-piece kit. Raydafon is a wholesale and OEM supplier of rotary cutter gearboxes from its factory in Ningbo, China.

Rated Power45HP

Ratio1:1.47

Input Shaft1-3/8"

Output Spline12T

What Is a Rotary Cutter Gearbox?

Product Definition

A rotary cutter gearbox is the speed-reducing drive unit that sits on top of a rotary cutter deck, between the tractor PTO shaft and the blade carrier. The tractor PTO turns at 540 rpm; the gearbox reduces that to the blade speed the cutter is designed for. In this 45 HP unit, the reduction is 1:1.47, which is a common ratio for 4' and 5' cutters where the blade tip speed needs to stay within a specific band for safe, clean cutting without excessive rotor inertia.

The shear pin is the defining feature. The 1-3/8" input shaft has a 1/2" hole drilled through it near the yoke end. A shear bolt passes through both the PTO yoke and the shaft. When the blade strikes a stump, rock or fence post, the shear bolt fails before the gear teeth do. Replacing a shear bolt takes two minutes; replacing a stripped gear set takes the cutter out of service for days. This is why the shear-pin design remains the standard for agricultural rotary cutters even where slip clutches are available.

The output shaft is splined rather than keyed because the blade carrier must be positively locked against rotation while transmitting high torque and absorbing shock loads. The 1-1/2" 12-spline output matches the blade hub found on most 4' to 6' cutters. The 1" castle nut and cotter pin hold the blade pan onto the splined shaft; a castle nut is used instead of a nylon lock nut because it provides mechanical locking that does not loosen under vibration.

45 HP Rotary Cutter Gearbox — Full Specification

Technical Data

The table below lists the complete specification of the 45 HP Rotary Cutter Gearbox. Before ordering, measure the input shaft, output spline count and mounting bolt pattern on the existing gearbox and compare against the values below.

Complete specification — 45 HP shear-pin rotary cutter gearbox
Parameter	Value
Gearbox Type	Shear-pin rotary cutter gearbox, single-stage reduction
Rated Power	45 HP (maximum continuous input)
Reduction Ratio	1:1.47
Input Shaft	1-3/8" smooth shaft with 1/2" shear bolt hole
Input Shaft Extension	3" from housing face to yoke end
Shear Bolt Size	1/2" diameter
Output Shaft	1-1/2" diameter, 12-spline
Output Spline Outside Diameter	1-9/16"
Output Shaft Overall Length	4-1/2"
Output Spline Length	2-3/4" from base of output cap to end of splines
Blade Pan Fastener	1" castle nut with cotter pin (nut included)
Mounting Bolt Pattern	4-3/4" center-to-center, 4 holes for 5/8" bolts
Alternate Bolt Pattern	6-1/2" (4) 5/8" holes with 5" center hole for shaft assembly
Overall Gearbox Height	9-1/2" from mower deck to top of gearbox
Weight	47 lbs (21.3 kg)
Housing Material	Cast iron
Gear Material	Hardened steel, single-stage pair
Lubrication	Gear oil bath (SAE 80W-90 or EP-90 typical)
Compatibility	Fits most 4', 5' and some 6' rotary cutters
Shaft Kit Contents	Input shaft + input gear + output shaft + output gear (matched set)
Customization	OEM ratios, shaft dimensions and bolt patterns available
Certification	ISO 9001 manufacturing system
Origin	Ningbo, China

45 HP rotary cutter gearbox shear pin input 1-1/2 inch 12 spline output — **45 HP Rotary Cutter Gearbox — Assembled Unit** The cast iron housing carries the 1-3/8" smooth input shaft with the 1/2" shear bolt hole on one side and the 1-1/2" 12-spline output shaft on the bottom. Mounting holes at the four corners use 5/8" bolts on a 4-3/4" center-to-center pattern. The 1" castle nut on the output shaft (visible in the assembly) secures the blade pan and takes a cotter pin.

Why Specify the Raydafon 45 HP Rotary Cutter Gearbox?

Design Advantages

Six design decisions separate this gearbox from a generic replacement. Each one is measurable in the field.

Shear Pin Protects the Gear Train

The 1-3/8" input shaft has a 1/2" shear bolt hole drilled through it near the yoke end. When the blade strikes an obstruction, the shear bolt fails in one clean break before tooth load reaches a level that would strip the gear teeth. Replacing a shear bolt costs under a dollar and takes minutes.

Matched Shaft and Gear Kit Only

The input shaft, input gear, output shaft and output gear are ground as a matched set. Raydafon does not sell the input or output shafts separately, because a new shaft paired with a used gear has a mismatched wear pattern that causes noise and premature failure. Buying the kit once prevents a second repair six months later.

1:1.47 Ratio — Blade Speed Within Design Band

The 1:1.47 single-stage ratio delivers the blade tip speed band that most 4' and 5' cutters are designed around. Too high a ratio increases rotor inertia and the risk of blade throw; too low a ratio leaves material uncut. The 1:1.47 ratio is the crossover point where most OEMs land for this cutter class.

Cast Iron Housing — Vibration Damping and Rigidity

Cast iron absorbs vibration more effectively than aluminium and holds gear centre distances rigidly under shock load from blade impacts. This is why agricultural gearboxes are almost universally cast iron even though aluminium would save weight. The 47 lb housing weight is a deliberate trade for durability.

IEC & SAE 1-3/8" Input Standard

The 1-3/8" smooth input shaft is the SAE standard for Category 1 and Category 2 tractor PTO yokes in North America and much of the export market. The 1/2" shear bolt hole position matches standard yoke geometry, so any standard PTO shaft end fits without modification.

ISO 9001 Manufacturing and Traceability

Every gearbox is assembled in Raydafon's Ningbo factory under an ISO 9001 quality system. Gear tooth profile, case depth and housing bore concentricity are checked in-process. Batch material certificates are retained and available on request with the shipment.

rotary cutter gearbox internal gear layout single stage reduction — **Internal Layout — Single-Stage Reduction Gear Pair** The gearbox contains one reduction stage: the input gear on the 1-3/8" shaft meshes with the output gear on the 1-1/2" splined shaft. Both gears are hardened steel with ground tooth flanks. The input and output shafts are supported by tapered roller or deep-groove ball bearings seated in bored housings, held concentric to maintain correct backlash as the gearbox heats up under load.

Where the 45 HP Rotary Cutter Gearbox Is Used

Applications

The 45 HP shear-pin gearbox is specified on rotary cutters in agricultural, municipal and roadside maintenance work. The applications below are the ones most often quoted on a Raydafon enquiry.

Agricultural pasture maintenance

Mowing pasture, hay aftermath and set-aside land with 4' and 5' rotary cutters behind compact and utility tractors in the 25-45 HP range.

Roadside and municipal maintenance

Cutting grass verges, ditch banks and municipal green spaces where a shear-pin gearbox protects the drive when the blade encounters road debris.

Orchard and vineyard mowing

Inter-row mowing in orchards and vineyards where the 1:1.47 ratio and 12-spline output match the blade carrier on narrow cutters.

Rough-cut land clearing

Clearing brush, saplings and overgrown fields where the shear pin is the primary protection against blade strike damage.

Equipment dealer aftermarket stock

Wholesale inventory for agricultural equipment dealers, repair shops and parts distributors stocking common rotary cutter gearbox replacements.

OEM rotary cutter assembly

Volume supply for rotary cutter manufacturers who need a matched gearbox and shaft kit integrated into a new cutter assembly line.

Rotary Cutter Gearbox Compatibility and Replacement Guide

Before You Order

A rotary cutter gearbox is not a universal part. Before ordering, confirm the four checks below against the existing gearbox on the machine. If all four match, this 45 HP gearbox is a direct replacement. If any do not match, send the dimensions and Raydafon will cross-reference to a suitable configuration.

Four-point compatibility check before ordering
#	Check	This Gearbox Value	How to Measure
01	Input shaft	1-3/8" smooth with 1/2" shear bolt hole	Measure the outside diameter of the input shaft at the PTO yoke end; check for a shear bolt hole
02	Output shaft	1-1/2" 12-spline, 4-1/2" overall length	Count the splines and measure the outside diameter across the splines
03	Mounting bolt pattern	4-3/4" center-to-center, 4 holes for 5/8" bolts	Measure distance between opposite bolt hole centers; check bolt diameter
04	Overall height	9-1/2" from deck to top	Measure from the mower deck top surface to the top of the gearbox housing

How to Order the 45 HP Rotary Cutter Gearbox

Ordering Inputs

To confirm the correct configuration and issue a wholesale or OEM quotation, Raydafon needs the five items below. For a straight replacement of an existing unit, a photo of the gearbox nameplate plus the four compatibility measurements is usually sufficient.

01Photo of the existing gearbox or its nameplate

02Input shaft diameter and shear bolt hole size

03Output shaft diameter and spline count

04Mounting bolt pattern center-to-center distance

05Quantity and required delivery date

rotary cutter gearbox mounting bolt pattern 4-3/4 inch centers — **Mounting Bolt Pattern and Output Shaft Detail** The four corner mounting holes are drilled for 5/8" bolts on a 4-3/4" center-to-center pattern. An alternate 6-1/2" pattern is also available with a 5" center hole to clear the output shaft assembly. The output shaft carries the 1" castle nut and cotter pin that retain the blade pan.

Talk to Raydafon About Your Rotary Cutter Gearbox Requirement

Whether you are replacing a worn shear-pin gearbox on a 4' or 5' cutter, stocking wholesale inventory for a dealer network, or specifying a gearbox for a new rotary cutter design, Raydafon can quote the 45 HP unit or an OEM-matched configuration to your input shaft, output spline, ratio and bolt pattern requirements. Wholesale and OEM quantities supplied directly from the Ningbo factory.

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