The Jeweler's Complete Guide to Cratex Finishing

The Jeweler's Complete Guide to Cratex Finishing

If you've ever wondered why your polished jewelry still shows scratches, why your solder joints are still visible after buffing, or why your cast pieces never look as clean as the pros' — the answer is almost always the same: you're skipping steps between fabrication and polish.

This guide covers everything you need to know about using Cratex rubber-bonded abrasives for jewelry finishing. From understanding the grit system to choosing the right shape for every application, this is your reference for getting professional results consistently.

Understanding the Grit Progression

Cratex uses a four-grit, color-coded system. Each grit removes the scratch pattern left by the previous one. Skip a grit and those scratches follow you all the way to the final polish.

🟢 Coarse (Green)

Heavy material removal. Use for: deep scratches, heavy sprue marks, rough casting surfaces, reshaping. Don't start here unless you have to — on precious metals, Coarse removes material fast and the deep scratch pattern takes extra steps to eliminate.

🟤 Medium (Brown)

The workhorse grit. Use for: general post-fabrication cleanup, moderate tool marks, solder joint leveling, fire scale removal. This is where most jewelry finishing starts.

🔴 Fine (Red)

Refinement. Use for: removing Medium grit scratches, pre-polish surface prep on harder metals, detail work near set stones. The scratch pattern from Fine is barely visible to the naked eye.

⚪ Extra Fine (White)

Final prep before polishing compound. Use for: the last step before rouge/ZAM/Fabulustre, removing Fine grit scratches, producing a smooth, uniform surface ready for mirror finish. After Extra Fine, your polishing compound has almost nothing left to do.

Beyond Extra Fine: MX Wheels

For jewelers chasing a true mirror finish on precious metals, Cratex MX wheels are even finer than Extra Fine. They bridge the gap between abrasive finishing and polishing compound, producing a surface so smooth that polish brings it to mirror in seconds rather than minutes.

Choosing the Right Shape

Every Cratex shape is designed for specific geometries. Using the right shape means faster work, better results, and less risk of damaging your piece.

Wheels (Mounted)

For: Broad, accessible surfaces — ring exteriors, pendant faces, bracelet links, band shanks.

How: Work tangent to the surface. The wheel follows curves naturally. Moderate speed (8,000–15,000 RPM), light pressure.

Points — Bullet

For: Curved surfaces, transitions, ring interiors, prong tips, rounded bezels.

How: The rounded tip follows curves without catching. Use for any concave or convex geometry.

Points — Cylinder

For: Flat surfaces in tight spaces, channel walls, straight edges, flat bezel tops.

How: The straight sides give even contact. Work along the length of channels, not across.

Points — Flame

For: Concave areas, between prong bases, inside curves, bail attachments.

How: The taper reaches into tight spots while the wider section blends surrounding areas.

Points — Cone

For: Inside corners, V-shapes, deep recesses, tube interiors.

How: The pointed tip reaches where other shapes can't. Low speed, minimal pressure.

Sticks (Hand)

For: Controlled hand finishing anywhere a rotary tool would be too aggressive. Delicate filigree, thin wire, precision areas.

How: Direct pressure with your fingers. Work in consistent, overlapping strokes.

Blocks (Hand)

For: Flat surfaces where you want maximum control. Cast piece faces, broad flat bands, pendant backs.

How: Like a sanding block but won't load, curl, or leave inconsistent scratches.

Cones (Mounted)

For: Inside curves, concave surfaces, decorative bowls, inside corners of settings.

How: The taper lets you control depth of contact. Angle to match the curve you're finishing.

Finishing by Application

Ring Finishing

Exterior: wheels tangent to the curve. Interior: bullet points in long strokes. Start at Medium for most fabrication work. See our complete Ring Finishing guide.

Cast Cleanup

Sprue removal with Coarse, systematic smoothing with Medium, refinement through Fine and Extra Fine. Hand blocks for delicate pieces. See our Cast Cleanup guide.

Solder Joint Smoothing

Start one grit finer than you think. Light pressure, overlapping passes extending past the joint. Feather the transition zone. See our Solder Joint Smoothing guide.

Stone Settings and Detail Work

Match point shape to geometry. Work away from set stones. Lower speed around delicate elements. Hand sticks for filigree. See our Detail & Bezel Work guide.

Metal-Specific Tips

Sterling Silver

  • Start at Medium — silver is soft and Coarse removes material fast
  • Watch for fire scale (firescale appears as dark shadows during finishing) — Cratex won't remove deep firescale, address with pickle first
  • Extra Fine produces an excellent pre-polish surface on silver
  • MX wheels give silver a near-mirror finish before polishing compound

Gold (10k–22k)

  • Higher karat = softer metal. 10k can start at Medium; 22k should start at Fine
  • Gold work-hardens quickly under abrasion — use light pressure to avoid surface hardening that makes subsequent grits less effective
  • The rubber bond is ideal for gold because it won't embed particles in the soft surface
  • MX wheels are essential for fine gold work — the gap between Extra Fine and polishing compound is where scratches hide

Platinum

  • Platinum is tough and dense — it can handle Medium or even Coarse starting grits
  • Platinum won't load Cratex wheels the way it loads sandpaper — the rubber bond releases debris naturally
  • Work through all four grits methodically. Platinum rewards a complete progression.
  • The satin finish after Extra Fine is actually a popular final finish for platinum rings

Copper and Brass

  • Full four-grit progression works beautifully on copper alloys
  • These metals are forgiving — good for learning Cratex technique before working on precious metals
  • Copper can smear at high speeds with fine grits — moderate your RPM
  • Brass takes a beautiful polish after Extra Fine — often you can skip polishing compound entirely

Common Mistakes

  1. Too much pressure — The rubber bond does the work. Pressing hard generates heat, wears the abrasive faster, and can warp thin metal.
  2. Skipping grits — Each grit exists to remove the scratch pattern of the previous one. Skip one and those scratches survive to the final polish.
  3. Wrong speed — 8,000–15,000 RPM for most work. Higher for aggressive removal, lower for detail work near stones. Never exceed 25,000 RPM.
  4. Using rigid abrasives for curved work — Sandpaper and hard wheels flatten curves. Cratex rubber conforms to the shape of your piece.
  5. Expecting polish to fix finishing problems — Polish makes a surface shiny. It doesn't remove scratch patterns. If the surface isn't smooth before polish, it won't be smooth after polish — just shiny and scratched.
  6. Not cleaning between grits — Stray coarse particles in your fine grit leave deep scratches. Wipe or ultrasonically clean between grit changes.

The Cratex System for Flex Shafts

Every mounted Cratex product (wheels, points, cones) uses a standard 1/8" (3.175mm) shank. This is the standard collet size for:

  • Foredom flex shafts (all models)
  • Dremel rotary tools (with 1/8" collet)
  • NSK micro motors
  • Marathon handpieces
  • Any rotary tool or handpiece with a 1/8" collet

Mount the mandrel in your collet, finger-tighten the Cratex abrasive onto the screw mandrel, and you're ready to work. No adapters, no modifications.

Pro tip: Keep 3-4 mandrels loaded with your most-used grits and shapes. Swapping mandrels takes seconds; unscrewing and rescrewing abrasives takes minutes. Over a day at the bench, those minutes add up.

Get Started

Ready to upgrade your finishing? Here are the kits designed specifically for jewelry work:

Or browse the complete Jewelry Finishing collection to build your own setup.

Questions about which products fit your workflow? Drop us a line — we're happy to help.

Which Shape for Which Job?

Cratex point shape guide for jewelers

Each Cratex point shape is designed for specific jewelry applications. Match the shape to the geometry of your work.