Bead Blasting
Bead blasting propels glass or ceramic beads at a surface to produce an even satin matte texture without cutting into it aggressively.
- Part
- Finishing
- Revised
- 2026-08-11
At a glance
- Family
- Subtractive
- Typical tolerances
- Removes under 0.0005 in (13 µm) — generally treated as dimensionally neutral, but toleranced bores, threads and sealing faces should still be masked
- Surface finish
- 32–125 µin (0.8–3.2 µm) Ra, non-directional, depending on bead size and pressure
- Typical volumes
- 1 to millions of parts; automated cabinets are used above a few hundred pieces for cosmetic consistency
- Lead time
- Same day to 3 business days at a job shop; usually run in line with anodizing
- Materials
- Metal, Plastic
What it is
Bead blasting propels spherical glass or ceramic beads at a surface to produce an even, low-gloss satin texture. Because the media is round rather than angular, it peens the surface rather than cutting it — it removes very little stock, work-hardens the surface slightly, and leaves a dimpled finish with no directional lay.
It is the standard cosmetic prep for machined aluminum, and bead blast followed by Type II anodize is the finish on most consumer electronics enclosures, camera bodies and instrument housings. Typical results land in the 32–125 µin (0.8–3.2 µm) Ra range depending on bead size and pressure, and working pressure is usually 20–60 psi (1.4–4 bar) — well below what an aluminum oxide blast would use. The trade-off is that bead blasting is a texturing operation, not a cleaning operation: it will not strip heavy scale, rust or old coating, and it will not remove a deep tool mark.
How it works
- Deburr and clean first. Bead blasting hides fine tool marks but not burrs, chatter or scratches. Machining marks deeper than the blast texture stay visible, and burrs simply become rounded burrs. Deburr and degrease before the cabinet.
- Mask. Threads, reamed bores, bearing seats, sealing lands and any surface with a specified finish get plugs, caps or tape.
- Select bead size. Finer beads produce a smoother, tighter satin; coarser beads produce a deeper, more matte texture. Media is specified by size number or mesh range, and the choice is the single biggest determinant of appearance.
- Blast. Beads are propelled at 20–60 psi (1.4–4 bar) through a hand or automated nozzle at a consistent standoff and angle. Uniformity is everything on a cosmetic part: overlapping passes, dwell in one spot, or a changing standoff distance all show as banding or blotching under raking light.
- Blow off and inspect. Residual media is removed with clean, dry, oil-free air. Trapped beads in blind holes and threads become contamination later.
- Finish promptly. Blasted aluminum has a high-energy, active surface. It should move to anodize, chem film or paint quickly, and be handled with gloves in the meantime — fingerprints on freshly blasted aluminum are visible after anodizing.
Media control
Beads fracture in use. A broken bead has sharp edges and cuts instead of peening, so a cabinet with degraded media produces a progressively different finish. Production cosmetic work uses classifiers to remove fines and broken media, and specifies media replacement intervals. This is why the same drawing can produce visibly different parts from two suppliers.
Design guidelines
Specify the finish by sample, not by adjective
"Bead blast" on a drawing is not a specification. Cosmetic work needs the bead size or mesh range, the nozzle pressure, and — most usefully — an approved physical master sample that the shop matches against under a defined lighting condition. Ra alone does not capture the appearance difference between two blast setups that measure the same.
Expect 32–125 µin Ra and no directional lay
Bead blasting produces a non-directional, uniform texture in the 32–125 µin (0.8–3.2 µm) Ra band, which is why it hides the lay of a milled or turned surface so effectively. See the surface finish chart for where that sits relative to as-machined, ground and polished surfaces.
Do not use it to remove material or fix defects
Stock removal is negligible — typically well under 0.0005 in (13 µm) — so bead blasting cannot correct a dimension, remove a scratch, or clean heavy oxide. It is a texture operation applied to an already-correct surface.
Mask every toleranced and sealing feature
Even light peening degrades a reamed bore, a lapped seal face or a thread. Plug or cap them. Blind holes also trap beads, so provide drainage or plan for a wash step.
Watch soft materials and thin sections
Aluminum, copper, brass and plastics can retain embedded media, and repeated blasting of a thin panel will bow it through induced compressive stress. Reduce pressure and bead size on thin or soft parts.
Sequence it correctly with anodizing
Bead blast, then anodize — the anodic film is thin and transparent and reproduces the blast texture. Blasting after anodizing destroys the coating. If a part needs both a blasted cosmetic face and a masked conductive pad, plan the masking for both operations at once.
| Feature | Recommended | Limit | Why |
|---|---|---|---|
| Working pressure | 20–60 psi (1.4–4 bar) | Lower on thin or soft parts | Higher pressure fractures beads and embeds media |
| Achievable Ra | 32–125 µin (0.8–3.2 µm) | — | Set by bead size and pressure |
| Stock removal | < 0.0005 in (13 µm) | Not a material-removal process | Round media peens rather than cuts |
| Appearance control | Approved master sample | Ra alone is insufficient | Two setups at the same Ra can look different |
| Media condition | Classified, fines removed | — | Broken beads cut and change the finish |
| Sequence | Deburr, blast, then anodize | Never blast after anodizing | Blasting destroys the anodic film |
Cost drivers
Bead blasting is inexpensive per part in a cabinet and expensive per part when the appearance requirement is tight, because the cost is almost entirely operator time and reject rate.
- Cosmetic tolerance. A functional matte finish costs a fraction of a Class A cosmetic finish with no banding, blotching or overlap witness under raking light.
- Masking. Plugs and caps on threads and bores are hand labor per part.
- Part size and handling. Cabinet work on small parts is fast; large housings need a room, a manipulator, or robotic blasting.
- Media management. Classified media and scheduled replacement cost more than running media to destruction, but they are what makes lot-to-lot consistency possible.
- Consistency across suppliers. Qualifying a second source to match an existing master sample is a real engineering cost, and one reason cosmetic blast specs are hard to dual-source.
Cost-reduction tactics:
- Approve a physical master sample early and control it — this prevents the most expensive failure mode, which is a rejected cosmetic lot.
- Robotic or automated blasting pays for itself on cosmetic parts above a few hundred pieces because it removes operator variation.
- Reduce masked features by moving fitted surfaces onto a separate component.
- Specify bead size and pressure on the drawing so the process is reproducible rather than negotiated per lot.
- Where the surface is not visible, use a functional blast callout instead of a cosmetic one.
Questions
6 questionsWhat Ra does bead blasting produce?
Typically 32–125 µin (0.8–3.2 µm) Ra, with a non-directional texture, depending on bead size and nozzle pressure. Finer beads and lower pressure give a tighter satin; coarser beads give a deeper matte. Ra alone does not fully define the appearance, so cosmetic work should be controlled with an approved master sample.
How much material does bead blasting remove?
Very little — typically well under 0.0005 in (13 µm). Round media peens rather than cuts, so bead blasting cannot correct a dimension, remove a scratch, or strip heavy scale or old coating. It is a texturing operation applied to an already-correct surface.
Should I bead blast before or after anodizing?
Before. The anodic film is thin and transparent and reproduces the blast texture faithfully, which is why bead blast plus Type II anodize is the standard finish on machined aluminum enclosures. Blasting after anodizing destroys the coating.
Why do bead-blasted parts from two suppliers look different?
Bead size, nozzle pressure, standoff distance and — most often — media condition. Beads fracture with use, and broken beads cut instead of peening, so a cabinet running degraded media produces a progressively different finish. Specify bead size, pressure and an approved master sample to make the process reproducible.
Bead blasting or abrasive blasting with aluminum oxide?
Bead blasting for a uniform cosmetic satin with negligible stock removal, at 20–60 psi. Aluminum oxide blasting for cleaning, stripping and creating a deep anchor profile for coating, at 60–100 psi, with a much coarser resulting surface in the 125–500 µin (3.2–12.5 µm) Ra range.
Do I need to mask threads for bead blasting?
Yes for anything toleranced or sealing. Even light peening degrades a reamed bore, a lapped seal face or a thread flank, and blind holes trap beads that become contamination later. Plug or cap those features, or produce them after blasting.