Slide 003: Finishing, Sanding, and Applied Finishes on the Lathe¶
Slide Visual¶
Slide Overview¶
This slide covers the final steps in spindle turning: achieving a smooth surface through proper tool technique and sanding, then applying finishes while the workpiece is still on the lathe.
Instruction Notes¶
Surface Quality from the Tool¶
The best finishing technique is to produce a surface quality from the cutting tool that requires minimal sanding. The skew chisel's planing cut produces the smoothest surface possible—often requiring only light sanding starting at 220 grit or finer.
Factors affecting surface quality from the tool: - Tool sharpness: A freshly sharpened tool produces dramatically better surfaces - Cutting speed: Higher RPM (within safe limits) produces smoother cuts - Cutting technique: Shearing cuts (bevel-rubbing) produce cleaner surfaces than scraping - Wood species: Dense, fine-grained woods (maple, cherry) finish better than open-grained species (oak, ash)
Sanding on the Lathe¶
Grit progression: Start with the coarsest grit needed to remove tool marks (typically 120-150), then progress through each grit:
| Grit | Purpose | When to Use |
|---|---|---|
| 120 | Remove tool marks, torn grain | After roughing or scraping |
| 150 | Refine 120 scratches | Standard progression |
| 180 | Intermediate smoothing | Standard progression |
| 220 | Fine smoothing | After clean gouge/skew cuts |
| 320 | Pre-finish prep | Before oil or wax finishes |
| 400 | Final prep | Before friction polish or lacquer |
Sanding technique: - Reduce lathe speed to 500-800 RPM to prevent heat buildup and sandpaper loading - Hold sandpaper in a folded pad—never wrap around fingers - Move the pad along the length of the workpiece—avoid dwelling in one spot (creates a flat or a groove) - Sand with the lathe running, then stop the lathe and sand with the grain by hand to remove cross-grain circular scratches - Between grits, clean the surface with compressed air or a tack cloth
Applying Finishes on the Lathe¶
Friction Polish: A shellac-based liquid applied to the spinning workpiece. Apply a small amount to a cloth pad (not fingers), press against the wood at medium speed. The friction generates heat that melts and polishes the shellac. Produces an immediate high-gloss finish. Best for decorative items; not as durable as other finishes.
Oil Finishes: Danish oil, tung oil, or mineral oil. Apply liberally with a paper towel pad while the lathe rotates slowly (200-300 RPM). Allow to penetrate 5-10 minutes, then wipe off excess with the lathe running. Build 2-3 coats with light sanding (400 grit) between coats.
Wax: Carnauba wax or beeswax applied as a stick against the spinning workpiece, then buffed with a clean cloth pad. Often used as a top coat over oil for additional sheen and protection.
CA (Cyanoacrylate) Finish: Thin CA glue applied to the spinning workpiece in multiple coats, with accelerator between coats. Produces an extremely hard, high-gloss, waterproof finish. Popular for pens and small items.
Safety During Finishing¶
- NEVER use rags that can wrap around the workpiece—use small pads held firmly
- Keep finishing products away from open flames—friction can ignite volatile finishes
- Ensure adequate ventilation when using oil, lacquer, or CA finishes
- Dispose of oil-soaked rags properly (fire hazard—spontaneous combustion risk)
Key Talking Points¶
- Good tool technique reduces sanding time dramatically
- Always sand with the grain as a final step after power sanding
- Friction polish looks great but is not a durable finish for functional items
- CA finish is the gold standard for small turned items (pens, bottle stoppers)
Learning Objectives (Concept Check)¶
- Can students describe the correct sanding grit progression?
- Can students explain why hand-sanding with the grain is the final step?
- Do students understand the safety risks of applying finishes on the lathe?
Last Updated: 2026-03-19