Post-Processing CNC Parts — Sanding, Finishing, and Staining Wood

The CNC gets you 80% of the way. The last 20% — finishing — is what makes it look handmade-quality or mass-produced-quality. Here's the full process.

Sanding Sequence

Never skip grits — going from 80 to 220 leaves 80-grit scratches under a 220-grit surface that show up under stain.

Always sand with the grain for the final pass.

Raising the Grain

Before staining, raise the grain:

1. Wipe wood with damp cloth
2. Let dry fully (30 min)
3. Light sand with 220 grit
4. This prevents blotching and stain raising the grain unevenly

Staining

• Apply with a brush or cloth, working with the grain
• Let penetrate 2–5 min (check manufacturer direction)
• Wipe off excess before it dries
• Allow 24 hours to dry before topcoat

Blotch-prone woods (pine, cherry, maple): Apply a wood conditioner first.

Topcoats

V-Carve and Relief Carve Finishing

For carved pieces:

• Apply thinned finish first (50:50 poly:mineral spirits) to seal carved channels
• Full-strength topcoat over the top surface
• Don't sand into carved areas — you'll erase the crisp edges

Painted CNC Work

1. Sand to 150 grit
2. Spray filler primer (2 coats)
3. Sand with 320 grit
4. Apply paint (2–3 coats)
5. Clear coat if needed