Start by locating the cutterbar assembly – the 4.5-meter horizontal blade carrier sits at the front of the unit, secured by dual flange bearings on either end. These bearings (part #812-0456) must have a minimum clearance of 0.002 inches; anything looser risks misalignment and accelerated wear on the reciprocating sickle sections. Replace them immediately if play exceeds this tolerance.
The knife drive linkage, positioned beneath the main frame, transfers power via a forged crank arm connected to the pitman shaft. The crank arm’s pivot pin (part #812-0629) should measure 0.875 inches in diameter; undersized pins lead to shearing under load. Apply a thin coat of NLGI #2 grease to the pin bores during reassembly to prevent metal-to-metal contact.
Above the cutterbar, the hold-down clips (set of 7, part #812-0334) maintain blade engagement with the bar. Each clip must exert 12–15 lbs of pressure; test this by lifting the clip with a spring scale. If resistance falls outside this range, replace the set – uneven pressure causes streaking and uneven cut heights.
Inside the gearbox, the primary drive gear (part #812-0782) meshes with the countershaft pinion. Check gear teeth for pitting or spalling; a magnifying inspection should reveal no more than three chipped teeth per gear. Exceeding this threshold mandates replacement to avoid catastrophic failure. The countershaft itself rotates on sealed tapered roller bearings (part #812-0914), which require 14 ft-lbs of torque on the retaining nuts.
For electrical components, the PTO clutch solenoid (part #812-0552) engages at 12.4V; test with a multimeter set to 200 ohms – readings above 15 ohms indicate coil degradation. Replace the entire unit if resistance is out of spec. The wiring harness connectors at the solenoid should show no green oxidation; clean terminals with 220-grit emery cloth and apply dielectric grease to prevent corrosion.
Refer to the internal reference sheets labeled “Component Layout – Ih 12HP Hay Equipment” for exact placement of each sub-assembly. Critical dimensions are noted in millimeters on the side margins of the layout – deviations beyond ±0.5mm will disrupt blade synchronization. Use a feeler gauge when adjusting cutterbar pitch to maintain the 3/16-inch gap between hold-downs and the bar.
IH Hay Cutter Assembly Blueprint: Step-by-Step Reference
Locate the knife head guide plates (part #837461R91) at the cutterbar’s forward edge–misalignment here causes uneven cutting. Replace worn plates if grooves exceed 0.5mm depth; use a feeler gauge to verify clearance against the section holders. For the pitman arm (part #585730R91), check the eccentric bearing wear by rotating the flywheel: resistance above 12Nm indicates lubrication failure or bearing seizure. Apply lithium-based grease (NLGI #2) through the zerk fitting every 10 hours of operation.
Troubleshooting Common Wear Points
Inspect the drive belt tensioner (part #543289R91) for cracks–replace if stretch exceeds 1.5% of original length (measure between cog centers). The retainer springs (part #532167R91) should snap back without hesitation; fatigue failure is identified by a gap >2mm under 4.5kg load. For the cutterbar shoes, grind down burrs exceeding 0.3mm to prevent crop jamming, and ensure the hold-down clips (part #528345R91) sit flush with ≤0.1mm tolerance.
Finding IH Cutting Bar Blades and Protective Shields
Start by lifting the header unit slightly and securing it with a stable block–never rely on hydraulic pressure alone. The knife sections attach to the curved cutterbar at 3-inch intervals, each held by a single bolt through the center. Use a 9/16″ socket wrench to remove rusted fasteners; apply penetrating oil beforehand if threads resist. Inspect the underside for bent fingers: straighten them with pliers before reassembly to prevent uneven cutting.
| Component | Tool Required | Torque Spec (ft-lb) |
|---|---|---|
| Knife section bolts | 9/16″ socket | 22-25 |
| Guard clamp screws | 7/16″ wrench | 18-20 |
| Wear plates | 3/8″ Allen | 12-15 |
Guard plates mount above the knife sections in staggered pairs, secured by clamp screws at the leading edge. Loosen both screws on a single guard before removal–this prevents twisting the steel. Check the rubber inserts inside each guard; cracks or excessive wear indicate replacement. Clean debris from the groove using a narrow chisel or wire brush to ensure proper knife seat alignment when refitting.
Swap damaged knife sections only in pairs to maintain balance–mismatched lengths cause vibration. Mark the orientation of reversible sections with a scribe before disassembly; reinstall with the beveled edge facing forward for consistent cutting. Grease the knife head bearings every 10 hours of operation. Store spare sections vertically in a dry rack to prevent rust.
Spotting Weaknesses on Ih Cutter Bar Blades: Key Areas to Inspect
Check the leading edge of each blade segment first–it degrades faster than any other section. Measure the thickness with a caliper: anything below 3.5mm indicates excessive wear. Replace segments in pairs to maintain balanced cutting action.
Examine the rivet holes where sections attach to the bar. Elongated holes create play, causing misalignment and uneven cutting heights. If the hole diameter exceeds 6.2mm (original spec: 5.8mm), install reinforced rivets or swap the entire bar.
Inspect the underside of the bar where crop residue accumulates. Corrosion begins here, weakening metal before visible pitting appears. Use a wire brush to remove debris; apply a thin layer of grease after cleaning to prevent future buildup.
Look for chipped serrations along the cutting edge–these reduce cutting efficiency by 40% before becoming obvious. Run a fingernail across the edge; if it catches, sharpen or replace that segment immediately. Avoid grinding serrations–heat weakens the temper.
Test section movement by hand: each should pivot smoothly with no lateral play. If resistance is uneven, disassemble and clean the bar’s rail slots. Apply dry lubricant (never oil) to avoid gumming up the mechanism.
Finally, check the bar’s straightness with a string line. A deviation greater than 1.5mm over 30cm means bent rails–weld repairs risk cracking under vibration. Replace bent bars rather than risking thrown sections during operation.
Step-by-Step Replacement of Ih Hay Cutter Connecting Rods and Bushings
Begin by securing the cutter bar assembly on a stable workbench, ensuring the drive shaft is immobilized with clamps. Use a 19mm socket to remove the cap screws holding the pitman arm in place–there are four per side, torqued to 45-50 Nm. Mark the orientation of the arm relative to the eccentric shaft with a paint pen before disassembly to preserve alignment during reinstallation.
- Place the removed connecting rod on a soft surface to avoid damaging the bronze bushings.
- Inspect the eccentric shaft journals for scoring–replace if grooves exceed 0.1mm depth.
- Check the old bushings for wear: if inner diameter measures above 38.2mm (OEM spec: 38.0mm), install new ones.
Press out worn bushings using a hydraulic press with a 37mm mandrel. Heat the connecting rod body to 150°C for 5 minutes to expand the housing before pressing new bushings in–this prevents cracking. Ensure bushings are seated flush with the rod ends, with oil holes aligned within ±5° of the original position. Lubricate immediately with EP-90 gear oil to prevent corrosion.
Final Assembly Checks
Reattach the connecting rod to the eccentric shaft, tightening cap screws in a cross pattern to 47 Nm. Rotate the shaft by hand–resistance should be uniform; if binding occurs, disassemble and recheck bushing alignment. Apply grease to the zinc-coated ball joint before reconnecting to the cutter bar knife head. Test the mechanism at 50 RPM for 2 minutes, verifying smooth oscillation with no metallic noise.
- Verify torque specs: Replace all nylon-insert locknuts if reused more than twice.
- Adjust knife head clearance to 0.25mm using feeler gauges before field operation.
- Post-installation, run the unit for 10 hours before full load to seat new components.
Precision Guide to Replacing Drive Components on International Harvester’s Heavy-Duty Cutting Implement
Measure the existing V-belt’s outside circumference before removal–International Harvester specifies exact belt lengths in millimeters, not inches. Use a flexible steel tape to wrap around pulleys under light tension, then cross-reference the reading with the service manual’s 528 mm or 550 mm listings to avoid mismatches.
Inspect pulley grooves with a go/no-go gauge or a feeler set; wear exceeding 0.5 mm on the groove walls mandates replacement. Cast-iron pulleys on the cutter bar’s oscillating shaft typically last two seasons before flange edges erode, whereas drive pulleys near the gearbox often show micro-cracks from torque spikes.
Align the new belt so the printed marking faces outward; improper orientation reduces grip by 18%. Slide the belt onto the smallest diameter pulley first, then work outward to larger diameters while rotating the implement by hand–do not force, as lateral misalignment exceeding 1 mm causes premature edge wear.
Tension the belt by turning the spring-loaded idler bolt clockwise in 1/4-turn increments. The correct deflection is 20 mm mid-span when pressing firmly with a spring scale exerting 10 kg force; over-tensioning accelerates bearing failure in the main shaft bushings.
Lock the tensioner with a jam nut once calibration is verified. Clean any grease residue from pulley faces using isopropyl alcohol pads–even minor contamination reduces traction by 12%, increasing slippage during high-load cutting cycles.
Replace any cracked or glazed pulleys immediately; plastic composite models (often silver-grey) tolerate field debris better than steel but fracture under impact loads above 400 Nm. Verify pulley keyways with a magnifying loupe–burrs as small as 0.2 mm misalign shafts, causing vibratory stress fractures.
After installation, run the implement at half throttle for five minutes, monitoring for belt squeal or lateral drift. If drift occurs, shut down and reset pulley parallelism using a machinist’s square against shaft faces–angular deviation must remain under 0.3° to prevent uneven wear patterns.
Record the new belt’s run-in hours on a metal tag riveted to the gearbox housing; International Harvester’s recommended replacement interval is 150 work-hours regardless of appearance, as internal cord fatigue precedes visible delamination or fraying.