Bead Blasting Finish for Machined Parts
The uniform matte surface that cleans up machining marks and preps parts for anodizing — process, Ra, bead blasting vs sand blasting vs brushed, and cost.
IsoCNC Engineering Team
CNC Machining & DFM Engineers · Updated · 7 min read
On this page
Quick Answer
Bead blasting propels fine glass or ceramic beads at a surface to create a uniform matte finish. It typically lands at Ra 1.6–3.2 µm, removes machining marks and light burrs, and is the standard prep before anodizing. It is the cosmetic matte option — sand blasting is rougher, brushed is directional, and anodizing adds a protective oxide layer on top. Material removal is minimal (0.005–0.025 mm), so dimensions stay essentially unchanged.
The Uniform Matte That Looks Intentional
A freshly machined part has tool marks, a slight sheen, and fingerprints. Bead blasting erases all three. It propels fine glass or ceramic beads at the surface at high speed, lightly texturing it into a uniform, non-reflective matte. The result reads as a deliberate finish, not a raw part — which is why bead blasting is the go-to cosmetic treatment for aluminum enclosures, brackets, and consumer-facing components, and the standard surface prep before anodizing. This guide covers what bead blasting does, the Ra it hits, and how it stacks up against the other finishes.
Process and the Ra It Achieves
Bead blasting is a mechanical, media-based process — glass or ceramic beads are accelerated by compressed air and impact the surface, peening it into a fine matte. For machined parts the common target is Ra 1.6–3.2 µm (63–125 microinches), with smoother results down to 0.8–1.6 µm using finer media and tighter control. The exact finish depends on bead size, air pressure, and standoff distance, so the right way to spec it is a target Ra — not just "bead blasted." For the full Ra chart, see our surface finish guide. If you are weighing it against angular-media blasting, our sandblasting vs bead blasting comparison covers media, roughness, and dimensional impact.
What Bead Blasting Is Actually For
Uniform matte cosmetic finish. A clean, low-reflective surface that hides fingerprints and minor imperfections.
Removing machining marks. Blasting knocks down the light tool marks and handling marks that a raw part carries.
Light deburring and edge softening. It rounds off sharp edges and removes small burrs.
Surface prep before coating or anodizing. The matte, slightly textured surface gives anodizing and paint an ideal base to key onto. Where the goal is fatigue resistance rather than cosmetics, shot peening uses similar media to deliberately induce compressive residual stress.
Bead Blasting vs the Other Finishes
The matte finish has several neighbors, each doing a different job:
| Finish | Main effect | Typical use |
|---|---|---|
| Bead blasting | Uniform matte, light texturing, light deburr | Cosmetic finish, prep for coating |
| Sand blasting | More aggressive and rougher | Heavy cleaning or roughening |
| Brushed | Directional visible grain, not uniform matte | Decorative linear appearance |
| Anodizing | Adds oxide layer, color, corrosion resistance | Protective aluminum finish |
The practical tiebreakers: bead blasting for a uniform matte, sand blasting for aggressive cleaning, brushing for a directional grain, and anodizing for protection and color on aluminum. Bead blasting and anodizing are often used together — blast first for the matte, anodize second for the color and corrosion resistance.
Materials and Dimensional Effect
Bead blasting works on aluminum, stainless steel, and steel — aluminum especially, where it is the standard cosmetic finish, though softer alloys need careful control to avoid over-texturing or media embedding. On dimensions, material removal is minimal — around 0.005–0.025 mm overall — so the part essentially keeps its size. But it is not zero, so critical fits and tight-tolerance features should be masked or held out of the blast process. This is what makes bead blasting a safe cosmetic step for most parts and a planning item for precision ones.
Cost
Bead blasting is generally an economical finish, but the price spreads with geometry. Published estimates range from $1–5 per square foot, or $1–4 for small brackets, up to $15–45+ per complex part. The drivers are part size, whether critical features need masking, the media choice, and the finish spec. Treat those as planning ranges — the real number depends on your part. For the surface-finish decision across all options, see our surface finish guide and our brushed metal finish guide.
FAQ
What is bead blasting?
Bead blasting is a finishing process that propels fine glass or ceramic beads at a machined surface to create a uniform matte texture. The beads hit the surface at high speed, lightly texturing it and removing machining marks, light burrs, and fingerprints. The result is a clean, non-reflective, uniform finish that reads as deliberate rather than raw.
What surface finish (Ra) does bead blasting achieve?
For machined parts, bead blasting commonly targets Ra 1.6–3.2 µm (63–125 microinches), with smoother results down to about 0.8–1.6 µm achievable using finer media and tighter control. The exact Ra depends on the bead size, air pressure, and distance, so specify the target rather than just the word blasted.
What is bead blasting used for?
Four main jobs: a uniform, low-reflective cosmetic finish; removing light machining marks and fingerprints; light deburring and edge softening; and surface preparation before coating or anodizing. It is especially popular on aluminum for cosmetic parts, where it gives a clean matte base for a subsequent anodize.
Bead blasting vs sand blasting vs brushed — what is the difference?
Bead blasting gives a uniform matte with no directional grain. Sand blasting is more aggressive and rougher, for heavy cleaning or roughening rather than cosmetics. Brushed gives a directional linear grain, not a uniform matte. And anodizing is not a blasting at all — it is an oxide coating often applied after bead blasting for color and corrosion resistance. Our brushed metal finish guide covers the directional option.
Does bead blasting change part dimensions?
Minimally. Material removal is usually small — around 0.005–0.025 mm overall — so the dimensional effect is generally negligible but not zero. Critical fits and tight-tolerance features should be masked or held out of the blast process, especially on softer aluminum alloys.
How much does bead blasting cost?
It varies widely with part size, masking, media, and finish spec. Published estimates range from roughly $1–5 per square foot, or $1–4 for small brackets, up to $15–45+ per complex part. Treat those as rough planning numbers — the real cost depends on your part's geometry and whether critical features need masking.
Related Resources
CNC Machining Surface Finish: The Ra Chart, Explained
The CNC machining surface finish chart: Ra values in μm and μin, N1–N12 grades, what each process achieves, what…
Passivation of Stainless Steel: Process, Specs, and When Parts Need It
Passivation of stainless steel explained for machined parts: the chemistry, ASTM A967 and AMS 2700 methods, nitric…
GD&T Basics for CNC Machined Parts: The Symbols That Matter
GD&T basics for machined parts: the 14 symbols explained, feature control frames, datums, MMC bonus tolerance, true…
How to Outsource CNC Machining to China, Step by Step
How to outsource CNC machining to China, step by step: vet suppliers, compare landed cost, control quality remotely,…
Blasted, Anodized, or Brushed — Spec It
IsoCNC machines and finishes aluminum, stainless, and steel — bead blasting, brushing, anodizing, and more — to the Ra you spec. Send the drawing; an engineer reviews every RFQ, typically within 1–2 business days.