Ink rollers are the heart of your Komori Lithrone 40’s inking system. When they wear down — and they will — print quality takes a direct hit: uneven ink distribution, ghosting, streaking, and inconsistent colour density. The fix isn’t complicated, but it does require a methodical approach. This guide walks you through the replacement process for both form rollers and oscillator rollers on the Lithrone 40 series.

When to Replace Your Lithrone 40 Ink Rollers

Don’t wait for print defects to tell you the rollers are shot. A good preventive schedule catches them early. Here are the signs that replacement is overdue:

• Surface glazing: The rubber develops a hard, shiny surface that won’t hold ink properly. If washing with a good roller cleaner doesn’t restore a matte finish after 3–4 attempts, the roller is glazed beyond recovery.
• Loss of diameter: Lithrone 40 form rollers typically start at 60–68 mm diameter for the front positions and 54–60 mm for the rear. When you’ve lost more than 2.5 mm from the original specification, ink film transfer becomes unreliable.
• Swelling or softening: Chemical attack from aggressive washes causes the rubber to swell — you’ll feel it as a spongy texture and see ink piling in the swollen areas.
• Ends worn more than centre: This creates a crown effect where the centre touches but the ends don’t, producing lighter print at the sheet edges.
• Cracks or chunks missing: Any physical damage to the roller surface is a hard stop — replace immediately.

Tools and Preparation

Before you start, gather everything you’ll need. Nothing slows down a roller swap like hunting for a missing spanner halfway through:

• Full set of metric Allen keys (3–10 mm)
• Torque wrench (for bridge clamp bolts — overtightening cracks the roller journal)
• Feeler gauge set (0.05–0.50 mm range)
• Clean lint-free rags
• Roller setting gauge or stripe-test ink (a good water-soluble blue works well)
• New rollers — make sure they’re the correct diameter for your press configuration
• Workshop gloves (keep oil off the new rubber)
• Plastic scraper or wooden stick (never metal on the roller surface)

Step 1: Remove the Old Rollers

Start with the press in a safe state — main power off, locked out if your shop requires it. Work from the top of the inking unit down. On the Lithrone 40, the ink roller train typically has four form rollers (riding directly on the plate), two to three oscillator/distributor rollers, and a rider roller at the top.

For form rollers: Loosen the bridge clamp bolts on both ends — these are usually M6 or M8 Allen heads on the Lithrone 40. Do not remove them completely; just back them out enough that the roller journal slides free. Support the roller with one hand as you loosen the second side — these rollers weigh 8–12 kg each and will drop if you’re not careful. Slide the roller out toward the operator side.

For oscillator rollers: These are more involved. The oscillator has a drive gear on the gear side and an eccentric bearing housing on the operator side. Mark the timing position of the gear with a paint pen before removal — getting the oscillation timing wrong causes ink distribution problems that are maddening to diagnose later. Remove the gear-side bearing cap, then the operator-side eccentric lock ring. The oscillator shaft slides out through the gear side.

Step 2: Clean the Mounting Surfaces

While the rollers are out, you have rare access to the roller mounts and journals. Clean every bearing seat, journal bore, and mounting surface thoroughly. Any old ink, grease, or corrosion left behind will prevent the new roller from seating properly and throw your stripe settings off.

Check the bearing surfaces for scoring or pitting. If you find damage, now is the time to replace those bearings — a new roller in a worn bearing will wear unevenly and you’ll be back here in half the normal service life.

Step 3: Install the New Rollers

Install in reverse order — oscillators first, then riders, then form rollers from top to bottom:

1. Oscillator rollers: Slide the new oscillator in from the gear side, align your timing mark, and seat the bearing housings. Torque the bearing cap bolts to Komori’s specification — typically 25–30 N·m for M8 bolts on these machines. If you don’t have the exact spec, snug plus a quarter turn is safer than guessing high.
2. Form rollers: Position the roller between the bridges, insert the journal into the operator-side bearing first, then the gear side. Tighten the bridge clamp bolts finger-tight initially — you’ll need to adjust position during setting.
3. Handle with care: New rubber is soft and easily nicked. Keep the roller wrapped until the moment you’re ready to install it, and never let it rest against sharp metal edges.

Step 4: Set the Roller Stripes

This is the step that separates a good roller change from a great one. The Lithrone 40 uses a parallel roller system — form rollers contact both the plate cylinder and the oscillator above them. Both stripes must be even across the full roller width.

Apply a thin, even film of stripe-test ink to the plate cylinder (or the oscillator, depending on which contact you’re setting first). Bring the form roller into contact using the adjustment screws — turn both sides evenly. Back off, check the stripe width. On the Lithrone 40:

• Form roller to oscillator stripe: 3–4 mm wide, even end to end
• Form roller to plate stripe: 4–5 mm wide, even end to end

If the stripe is wider on one end, adjust that side’s setting screw to bring the roller parallel. The feeler gauge method works too — target 0.10 mm clearance with the plate for initial setting, then verify with stripe-test ink. Always run a stripe test after adjusting — it catches errors the feeler gauge misses.

Step 5: Run-In and Final Checks

Don’t jump straight to a production job after the swap. Run the press at slow speed (3,000–4,000 iph) for 15–20 minutes with ink in the train but no paper feeding. This lets the new rubber settle and distributes the ink film evenly. Listen for any unusual noise — a rhythmic clicking often means a roller isn’t quite parallel and is knocking against its contact surface.

After run-in, recheck your stripes. New rubber compresses slightly in the first hours of use, and you may need to back off the setting screws by a quarter turn. Print a test sheet at full production speed and check for even ink coverage across the sheet — pay special attention to the lead and tail edges, where roller bounce from worn bearings shows up first.

Common Mistakes to Avoid

• Skipping the timing mark on oscillators: If the oscillation phase is off, you’ll see a diagonal ink starvation pattern that no amount of adjustment will fix. You’ll have to pull the oscillator out and re-time it.
• Overtightening bridge clamps: The roller journal is typically hardened steel, but the bridge is cast iron. Crack the bridge and you’re looking at a much more expensive repair.
• Using the wrong stripe width: Too narrow and you starve the plate of ink. Too wide and you get excessive heat build-up, which degrades the rubber faster and can cause emulsification problems.
• Mixing old and new rollers: If you only replace one form roller while three others are at 85% of their original diameter, the new roller will carry a disproportionate share of the contact pressure. Replace form rollers as a set when possible.

Getting the Right Replacement Rollers

The quality of your replacement rollers directly determines how long this job lasts and how good your prints look. Aftermarket ink rollers manufactured to OEM specifications offer the same performance as factory parts at a fraction of the cost. When ordering, always confirm the roller diameter and length match your specific Lithrone 40 configuration — Komori produced several variants over the years, and a mismatch wastes time and money.

For shops running multiple press brands, RelyOffset carries a full range of Komori-compatible replacement parts including rollers, doctor blades, grippers, and dampening system components — all manufactured to meet or exceed OEM dimensional tolerances.

If you need help identifying the correct roller for your serial number or want to discuss bulk pricing for a full roller set replacement, contact our support team with your press details.

Disclaimer: RelyOffset parts are OEM-compatible aftermarket components. Brand names and model designations including Komori and Lithrone are trademarks of their respective owners and are used for compatibility identification purposes only.