Flex Hone Cylinder Ball Hone for Coated Ball Hone Cylinder Walls: Avoid Coating Damage
How to Safely Deglaze Nikasil, Chrome, and Other Coated Engine Bores
Coated cylinder walls—Nikasil, hard chrome, and other plated surfaces—offer exceptional wear resistance and reduced friction. But when it comes time to deglaze or refresh the surface for new rings, the wrong approach can destroy the coating and ruin an expensive cylinder.
This guide explains how to use a flex hone cylinder ball hone safely on coated ball hone cylinder walls, what abrasive to choose, and what to avoid at all costs.
What Are Coated Cylinder Walls?
| Coating Type | Description | Common Applications |
|---|---|---|
| Nikasil | Electroplated nickel-silicon carbide coating, 3-4 thousandths of an inch thick | High-performance motorcycles, snowmobiles, Porsche, BMW |
| Hard Chrome | Electroplated chromium layer | Industrial engines, some motorcycle cylinders |
| Mercosil / Alusil | Silicon particles in aluminum matrix | Many modern automotive engines |
These coatings are extremely hard and wear-resistant. But they are also thin—Nikasil is only about 0.006 inches thick—and brittle. A damaged coating cannot be repaired; the cylinder must be stripped and re-plated or replaced.
The Risk: Coating Damage from Improper Honing
Using the wrong ball hone for cylinder can:
| Damage Type | Cause | Consequence |
|---|---|---|
| Coating flaking | Abrasive too aggressive or catches on port edges | Rings cannot seal; cylinder must be re-plated |
| Coating removal | Removing too much material | Oversized bore, piston fit issues |
| Scratches | Wrong abrasive type | Poor ring sealing, oil consumption |
| Edge damage | Hone catches on port or chamfer edges | Coating delamination |
Critical warning: If the Nikasil plating is chipped, nicked, cut-through, has worn spots, or is showing signs of wear, do not use a flex hone. Strip and re-plate the coating, or replace the cylinder entirely.
The Right Tool: Flex Hone Cylinder Ball Hone with Aluminum Oxide
For coated cylinders, the flex hone cylinder ball hone with aluminum oxide (AO) abrasive is the recommended tool.
Why Aluminum Oxide?
| Abrasive Type | Suitability for Coated Cylinders | Reason |
|---|---|---|
| Aluminum Oxide (AO) | ✅ Recommended | Softer abrasive that conditions without removing coating |
| Silicon Carbide (SC) | ❌ Not recommended | Too aggressive; can damage thin coating |
| Diamond | ⚠️ For re-plating only | Removes metal, not suitable for deglazing |
| Boron Carbide | ✅ Professional honing | Used by Sunnen for Nikasil stones |
For deglazing Nikasil engine cylinders, 240-grit aluminum oxide flexible hones are the industry standard.
Recommended Grit Selection
| Application | Grit | Abrasive |
|---|---|---|
| Nikasil deglazing | 240 AO | Aluminum Oxide |
| Hard chrome deglazing | 240 AO | Aluminum Oxide |
| Light surface conditioning | 320 AO | Aluminum Oxide |
| Aluminum bore finishing | 240 AO | Aluminum Oxide |
Safe Honing Procedure for Coated Cylinders
Before You Start
| Step | Action |
|---|---|
| 1 | Inspect the coating thoroughly. Look for chips, flaking, cut-through, or worn spots |
| 2 | If any damage is found, do not hone—re-plate or replace |
| 3 | Measure the bore to verify it is within specification |
| 4 | Select a 240-grit aluminum oxide flex hone |
Honing Steps
| Step | Action |
|---|---|
| 1 | Apply generous lubricant (honing oil or 10W-30) |
| 2 | Insert the rotating flex hone into the bore |
| 3 | Use light pressure only—the coating is thin |
| 4 | Hone for only 5-10 strokes—just enough to break the glaze |
| 5 | Remove the hone while still rotating |
Cleaning After Honing
| Step | Action |
|---|---|
| 1 | Clean with hot, soapy water and a cleaning brush |
| 2 | Dry the cylinder thoroughly |
| 3 | Wipe with a lint-free cloth coated with light oil or mineral spirits |
Common Mistakes to Avoid
| Mistake | Why It's Dangerous |
|---|---|
| Using silicon carbide on Nikasil | Too aggressive; can damage the thin coating |
| Honing a damaged coating | Will cause flaking and require re-plating |
| Too many strokes | Removes too much material; coating is only 0.006" thick |
| Using a ball hone on out-of-round cylinders | Flex hones follow irregularities; may cause uneven coating removal |
| Honing with insufficient lubricant | Heat generation can damage coating |
When to Avoid Flex Honing Altogether
A flex hone cylinder ball hone is a finishing tool, not a repair tool. Do not use a flex hone on coated cylinders when:
-
The coating is chipped, flaked, or cut-through
-
The bore is out-of-round or tapered
-
The coating shows signs of wear or erosion
-
The cylinder needs significant material removal
In these cases, the cylinder must be stripped and re-plated, or replaced entirely.
Quick Reference: Coated Cylinder Honing
| Parameter | Recommendation |
|---|---|
| Abrasive type | Aluminum Oxide (AO) |
| Recommended grit | 240 |
| Tool | Flex hone cylinder ball hone (slightly oversized) |
| Lubricant | Honing oil or 10W-30 |
| Strokes | 5-10 (light deglazing only) |
| Maximum coating thickness | ~0.006 inches |
| When to stop | Immediately if coating damage is visible |
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