Cratex Grit Guide for Knife Makers
Cratex rubber abrasives come in four standard grits, each color-coded for easy identification. Most knife finishing tasks involve working through the grits sequentially — starting coarser and finishing finer. Here's what each grit does and when to use it.
COARSE — Green
Mesh: ~54 grit
The most aggressive Cratex grit. Use this when you need to remove material — not just polish it.
Knife making applications:
- Removing rust and heavy corrosion from restoration blades
- Knocking down rough tool marks or deep scratches
- Initial deburring after grinding
- Cleaning up badly misaligned solder joints
When to skip it: If your blade is already in decent shape from the belt grinder, you may not need coarse at all. Start with Medium instead.
MEDIUM — Dark Brown
Mesh: ~80 grit
The workhorse grit for most knife finishing tasks. Removes visible marks without being overly aggressive.
Knife making applications:
- General scratch removal after heat treat
- Blending and smoothing plunge lines
- Removing heat-treat discoloration
- Smoothing solder joints and guard fit-up
- Handle material shaping and smoothing
When to use it: This is your starting grit for most finishing work on a blade that's already been through the belt grinder and basic sandpaper progression.
FINE — Reddish Brown
Mesh: ~150 grit
Refinement grit. This is where your blade starts to look polished rather than just smooth.
Knife making applications:
- Pre-polish smoothing on blade flats
- Refining plunge lines after medium grit cleanup
- Finishing guard and bolster surfaces
- Achieving a consistent satin finish
When to use it: After Medium, before Extra Fine. This is the grit where you're no longer removing material — you're refining the surface.
EXTRA FINE — Grey-Green
Mesh: ~240 grit
The final Cratex grit. Use this for your last pass before stropping or buffing.
Knife making applications:
- Final blade polish
- Mirror finish prep (follow with compound and strop)
- Polishing decorative elements
- Final pass on visible hardware and pins
When to use it: This is your last step with Cratex. After Extra Fine, you're either done (satin finish) or moving to polishing compound and a strop/buffer for mirror finish.
The Full Progression
| Step | Grit | Color | What It Does |
|---|---|---|---|
| 1 | Coarse | Green | Remove material, rust, deep marks |
| 2 | Medium | Dark Brown | Smooth, blend, general cleanup |
| 3 | Fine | Reddish Brown | Refine, pre-polish |
| 4 | Extra Fine | Grey-Green | Final finish, polish prep |
Tip: You don't always need to start at Coarse. Assess your blade's condition after heat treat and sanding — most makers start at Medium or Fine with Cratex and work down to Extra Fine.
Tip: Buying one grit? You'll almost certainly want the next one too. Each step builds on the previous one, and skipping grits leaves visible scratch patterns from the coarser step.
Grit Selection for Jewelers
Working with precious metals? The same four-grit system applies, but your starting point and emphasis shift:
- Gold, Silver, Platinum: Start at Fine (reddish brown) for most work. Precious metals are softer than steel — Coarse and Medium are more aggressive than you need unless you're cleaning up heavy casting defects.
- Cast Cleanup: Start at Medium (dark brown) to remove sprue marks, investment bumps, and casting flash. Then step through Fine and Extra Fine.
- Solder Joints: Fine for initial blending, Extra Fine for invisible joints.
- Final Polish Prep: Extra Fine (grey-green) gets precious metals ready for rouge and a polishing wheel.
The key difference: jewelers spend most of their time in Fine and Extra Fine. Knife makers use the full range. Same system, different emphasis.