Bead Blasting Aluminum: How to Choose Glass Bead, Steel Shot, or Aluminum Oxide

Glass bead is the default media for cosmetic bead blasting on aluminum. It is spherical, softer than the oxides, and does not cut or discolor a 6061 or 7075 surface the way angular media does. Steel shot and aluminum oxide both have a place, but on soft aluminum they solve different problems: aluminum oxide when you need to strip or profile before coating, steel shot when the part is hard or needs peening instead of a finish.

The media itself is what three published standards control. MIL-PRF-9954D defines glass beads, ISO 11126-7 defines fused aluminum oxide, and ISO 11124-3 defines high-carbon cast-steel shot and grit. Each one specifies particle size, shape, density, and cleanliness. None of them specifies blast pressure, nozzle distance, or the final Ra you get on the part. That line matters, and this guide keeps it: standards tell you what the media is, process control and measurement tell you what the surface becomes.

This guide covers what bead blasting is on aluminum and how the bead blast finish is made, the three media that matter, how their grade and size systems work, how bead blasting compares to sandblasting, what the media standards do not control, and how blasting interacts with a later anodize step. It does not give a pressure-to-Ra recipe, because no media standard supports one.

1. What bead blasting does to an aluminum surface

Bead blasting drives spherical media against the metal with compressed air. Each bead leaves a shallow rounded dimple. Thousands of overlapping dimples scatter light in every direction, which reads as a uniform matte or satin surface on bead blasted aluminum and hides the directional tool marks left by milling or turning. On aluminum the effect is cosmetic and light: the surface texture changes, but bulk dimensions do not move the way they can under aggressive angular blasting.

Spherical media works by plastic deformation, not cutting. A glass bead pushes metal down and sideways at the impact point instead of shearing a chip off. Angular media like aluminum oxide does the opposite, its sharp edges cut and remove material, which is why the two produce different surfaces from the same machine. Glass bead holds part dimensions; aluminum oxide can open a tolerance.

There is a naming trap worth clearing up early. The rounded-media impact does put a thin layer of compressive stress into the surface, and some suppliers call any bead blasting peening. Controlled shot peening is a separate, specified process with Almen intensity, coverage, and saturation requirements. Cosmetic bead blasting on an aluminum housing is not that. MIL-PRF-9954D even carries Cleaning and Peening in its title, but the standard defines the glass bead media, not a peening process. Calling a decorative blast shot peening on a drawing invites a spec you did not mean to require.

EPOC CRAFTER engineering note: On machined 6061 housings we mask sealing faces, O-ring grooves, and tapped holes before blasting, because a blasted sealing surface and a blasted thread are the two features that most often come back as a fit or leak problem. Blasting works by line of sight, so deep pockets, cross-holes, and internal cavities blast unevenly or not at all. This is shop practice, not a requirement any of the three media standards imposes.

2. The three media that matter for aluminum

Six or seven media types show up in metal bead blasting charts. For a bead blasting finish on aluminum, the real decision is among three: glass bead, aluminum oxide, and steel shot. Each is defined by a published media standard that fixes what you are buying. None of those standards tells you what surface you will get on the part, and Section 6 holds that line. Here the standards do one job well, which is pinning down the media itself so a supplier cannot swap in something coarser or dirtier than the drawing intended.

2.1 Glass bead: the default for a cosmetic aluminum finish

Glass bead is the media to reach for first on a 6061 or 7075 part that needs an even matte or satin look. The beads are spherical soda-lime glass, so they deform the surface instead of cutting it, and they leave the base color of the aluminum alone. That is why a bead-blasted 6061 aluminum part keeps a neutral gray tone instead of picking up a cast from the media.

MIL-PRF-9954D is the specification that defines these beads. It sets 13 bead sizes, numbered MIL #1 (coarsest) through MIL #13 (finest), each with its own U.S. sieve distribution. It also fixes minimum roundness, which rises from 60% at the coarse end to 95% at MIL #13, and a specific gravity of at least 2.3. On the chemistry side it caps crystalline silica below 0.1% by weight, requires at least 62% amorphous silica, and limits arsenic to 75 ppm and lead to 100 ppm. The beads must be newly manufactured soda-lime glass, not recovered blasting media, and carry no silicone film and no more than 0.1% free magnetic iron.

Those numbers matter for one practical reason: they are what glass bead means when a supplier certifies to the standard. Roundness and cleanliness are the two that show up on aluminum. Below-spec roundness means more angular fragments in the mix, which start to cut instead of peen; a silicone or iron film transfers to the part and interferes with a later anodize or paint step. The standard controls the media so those failure modes stay out. It does not set a blast pressure or a target Ra, and MIL-PRF-9954D carries Cleaning and Peening in its title without defining a controlled peening process, so a cosmetic bead blast is not shot peening even when the beads meet this spec.

EPOC CRAFTER engineering note: For aluminum housings that will be anodized, we hold glass bead media to newly manufactured stock and keep a separate cabinet from steel media. A batch of beads that has picked up iron fines from mixed use reads fine in the cabinet and then shows as scattered dark specks after anodize, when it is too late to fix cheaply.

2.2 Aluminum oxide: when you need to strip or profile, not beautify

Aluminum oxide is the choice when the job is removing an oxide layer, stripping a coating, or leaving a toothed profile for paint to grip. The grains are angular and hard, so they cut. That makes them faster than glass bead at taking material off, and it also means they can open a tolerance and dull the surface instead of brightening it. On soft aluminum, aluminum oxide is a preparation step, not a finishing step.

ISO 11126-7 defines fused aluminum oxide as a blast-cleaning abrasive. It splits the media into Type A, brown, with at least 94% aluminum oxide and up to 4% titanium dioxide, and Type WA, whitish, with at least 99% aluminum oxide. It specifies eight particle-size ranges from 0.045 mm up to 2.80 mm, an apparent density of 3.9 to 4.0 x 10^3 kg/m3, a Mohs hardness of at least 6, moisture no higher than 0.2%, aqueous-extract conductivity at or below 250 uS/cm, and water-soluble chlorides at or below 0.0025%. It also requires no free silica.

Two cautions come straight from the standard. First, the F-grit codes people quote, like F24 or F36, are only an informative approximate cross-reference in Annex A of ISO 11126-7; they are not the standard’s own grade designation, which is a millimeter particle-size range. Ordering F36 and assuming it is an ISO 11126-7 grade skips over that. Second, the apparent density in the standard is exactly that, apparent density, not specific gravity, so it does not line up with the specific gravity number quoted for glass bead. The two media use different property names, and putting them in the same column as if they were one number is a mistake the comparison table in Section 3 avoids.

The brown color of Type A is the media’s own color. It describes the abrasive, not the finished aluminum surface, and aluminum oxide can leave a slight discoloration on the part. ISO 11126-7 sets no requirement for the appearance of the blasted aluminum, so any statement about final color or matte level has to come from process trials, not from this spec.

2.3 Steel shot and grit: for hard substrates and peening, not soft aluminum cosmetics

Steel shot and steel grit are built for harder work than a cosmetic aluminum pass. Shot is round and used to clean, descale, or peen; grit is angular and cuts. Both are dense and hard enough to embed in or distort soft aluminum, so on a 6061 or 7075 cosmetic part they are the wrong first choice. Where they earn their place on aluminum is a controlled peening application on a load-bearing part, and there the process is peening with its own spec, not the decorative blast this guide is about.

ISO 11124-3 defines high-carbon cast-steel shot and grit. It lists 14 shot grades, S280 down to S018, and 11 grit grades, G170 down to G007, each with a screening distribution given as cumulative percent retained. Standard shot hardness runs 390 to 530 HV; grit is offered in several hardness bands up to 700 HV and above. Apparent density is at least 7.0 x 10^3 kg/m3, roughly the density of steel and well above the oxides. The standard also fixes chemistry, with carbon at 0.80 to 1.2%, manganese 0.35 to 1.2%, silicon at least 0.4%, and sulfur and phosphorus each capped at 0.05%, plus microstructure and defect limits.

The hardness here is Vickers, HV. Aluminum oxide’s hardness in ISO 11126-7 is Mohs. Those are two different scales, and one does not convert cleanly to the other, so a comparison table cannot rank all three media on a single hardness column without misleading. That is why the table in the next section keeps each media on its own standard’s property and its own units.

EPOC CRAFTER engineering note: We keep steel media off the aluminum line entirely. Even setting aside the risk of denting a soft part, steel fines left in a shared cabinet transfer iron onto aluminum, and embedded iron on an aluminum surface becomes a corrosion site after the part goes into service. Cross-contamination between media families is a cleanliness problem before it is a finish problem.

3. Media selection table: match the media to the job, not to a single number

The table below puts the three aluminum media side by side. The left columns are what each media standard fixes. The right column is the decision, meaning what the media is for and when to pick it. The property rows stay in each standard’s own units on purpose, because glass bead specific gravity, aluminum oxide apparent density, Vickers hardness, and Mohs hardness are four different measurements and forcing them into one shared number would misrepresent all of them.

Particle shape	Spherical	Angular	Shot round, grit angular	Spherical peens and brightens; angular cuts and etches. Shape drives whether the surface gets smoothed or profiled
Size / grade system	13 sizes, MIL #1 to #13	8 size ranges, 0.045 to 2.80 mm	Shot S280 to S018, grit G170 to G007	Coarser grade means more texture and faster action; finer means smoother. Grades are not interchangeable across the three systems
Hardness	Not specified in the standard	Mohs 6 or higher	390 to 530 HV shot; up to 700+ HV grit	Harder media cuts harder substrates. Do not read Mohs and HV as one scale; they do not convert
Density	Specific gravity 2.3 or higher	Apparent density 3.9 to 4.0 x 10^3 kg/m3	Apparent density 7.0 x 10^3 kg/m3 or higher	Denser media hits harder at the same speed. Steel carries the most energy, glass the least, which is why glass is gentle on soft aluminum
Cleanliness controls	Under 0.1% crystalline silica, 100 ppm lead max, no silicone, 0.1% magnetic iron max	No free silica, chlorides 0.0025% max, conductivity 250 uS/cm max	Foreign matter and moisture limits, dry supply	Contamination transfers to the part and shows up after anodize or paint, so a certified media earns its cost on cosmetic aluminum
What the standard does NOT set	Blast pressure, final Ra, part appearance	Blast pressure, final Ra, part appearance	Blast pressure, final Ra, part appearance	None of the three specs a surface result. The finish comes from process control, covered in Section 6
Best fit on aluminum	Cosmetic matte or satin, keeps base color, holds dimensions	Strip coating, remove oxide, profile for paint	Hard substrates, controlled peening, not soft-aluminum cosmetics

Read the table by starting from the job, not the media. A cosmetic housing that has to keep its dimensions and take an even anodize points to glass bead: spherical, lowest density, cleanest control set for what happens after blasting. A part that needs old coating stripped or a paint-ready tooth points to aluminum oxide, with the understanding that it cuts and can move a tolerance. A hard steel part or a genuine peening requirement points to steel media, which is the wrong tool on a soft aluminum cosmetic surface.

The density row is the one that explains the most on aluminum. Steel media at roughly 7.0 x 10^3 kg/m3 carries far more impact energy than glass bead at a specific gravity of 2.3, so the same cabinet and the same pressure hit a soft aluminum part much harder with steel. That energy gap is the physical reason glass bead holds dimensions on a thin-wall 6061 part while steel or coarse aluminum oxide can deform it or open a feature that carries a tight tolerance. When the part has features that need to stay put, the media choice is part of protecting them, and which CNC features need tighter control is worth settling before the finish gets specified.

EPOC CRAFTER engineering note: Buyers push back on the hardness row more than any other. Someone sees Mohs 6 for aluminum oxide next to 390 to 530 HV for steel shot and asks which is harder. They are measured on scales that do not translate, so the honest answer is that the question is the wrong one. The decision on aluminum is shape and density first, because those govern whether the surface is peened or cut and whether the part keeps its size. Hardness only settles whether the media can work a given substrate at all, and all three can work aluminum. What separates them on aluminum is what they do to it, not a hardness ranking.

4. Grade and particle size, without the myths

Media size controls how much texture a blast leaves, and it is where most drawing confusion starts. Each of the three media uses a different sizing system, the three systems do not cross-convert, and none of them predicts a surface roughness number on its own. Getting the grade language right is what keeps an RFQ from specifying something the supplier reads differently than you meant.

Glass bead uses the MIL number. MIL-PRF-9954D runs from MIL #1, the coarsest, to MIL #13, the finest, and each number is a defined U.S. sieve distribution, not a single diameter. Aluminum oxide uses a millimeter particle-size range under ISO 11126-7, one of eight bands from 0.045 mm to 2.80 mm. Steel media uses a grade code under ISO 11124-3, where a shot grade like S110 or a grit grade like G040 maps to a nominal particle size. Three media, three sizing languages, and a #8 glass bead has nothing to do with a G040 steel grit or an F40 oxide.

The F-grit code deserves its own warning. Aluminum oxide is often ordered as F24, F36, F40 and so on, and those look like ISO grades but are not. ISO 11126-7 lists the F-series only in an informative annex, as an approximate cross-reference to its own millimeter ranges, and the standard states the equivalence is approximate and should not be read as the grades being equal. The specification’s own designation is the particle-size range in millimeters. Writing F36 per ISO 11126-7 on a drawing mixes a code the standard does not adopt with a standard it does not belong to.

One point trips up more drawings than any other: a media grade does not equal a surface roughness. Nothing in MIL-PRF-9954D, ISO 11126-7, or ISO 11124-3 maps a bead size or grit grade to a resulting Ra on the part. The finish depends on the substrate, the blast pressure, the standoff distance, the nozzle, the dwell time, the number of passes, and whether the media is new or worn, none of which the media standards touch. A finer bead trends toward a smoother finish and a coarser bead toward more texture, but that is a direction, not a value. Specifying MIL #10 to achieve Ra 1.6 um looks like a controlled requirement but is not one, because the grade does not carry the Ra with it.

The practical move is to specify the media grade and the finish target as two separate things, and to let a sample settle the appearance. Call out the media and grade so the supplier buys the right abrasive, then either give a boundary sample for the look or reference an Ra range from the surface roughness chart that the shop confirms it can hold with that media through a trial. Treating the grade as if it guarantees the roughness does not work. The difference between a media spec and a process result is why boundary samples exist on blasted parts.

EPOC CRAFTER engineering note: When a drawing lands with a bead size tied to an Ra value, we quote the media and treat the Ra as a target to confirm on a first-article coupon, not as a number the grade delivers by itself. On the same 6061 part, a worn charge of beads and a fresh charge at the same nozzle pressure read differently under a profilometer, which is why the standard stops at the media and the shop owns the result. A first coupon in the actual media, at the actual pressure, is how you lock the look.

5. Bead blasting vs sandblasting for aluminum

Sandblasting and bead blasting, or sand blasting and bead blast finishing, get used as if they were the same process, and on aluminum the bead blast vs sandblast difference decides whether the part keeps its dimensions or loses them. The glass bead blasting vs sandblasting split is simple: bead blasting drives spherical media, usually glass bead, that peens and brightens, while sandblasting drives angular media, historically silica sand and now more often aluminum oxide, that cuts and etches. Same cabinet, same compressed air, opposite effect on the surface.

On aluminum, what each does to the part is what separates them. Bead blasting leaves an even matte or satin finish, keeps the base color, and removes very little material, so it holds tolerances on soft 6061 and 7075. It is slow at stripping heavy coatings and does not leave a profile for paint to key into. Sandblasting with aluminum oxide cuts fast, strips coatings and corrosion, and leaves a toothed profile for paint or primer. On soft aluminum that same aggression removes material, can distort thin walls, and dulls the surface instead of brightening it.

The silica point is worth stating plainly because it changed industry practice. Traditional silica sand carries a respirable crystalline silica hazard, and it has largely been replaced by aluminum oxide and other media for that reason. When someone says sandblasting on an aluminum job today, the media in the cabinet is usually aluminum oxide, not sand. That is also why MIL-PRF-9954D caps crystalline silica in glass bead below 0.1%, and why ISO 11126-7 requires aluminum oxide to contain no free silica: the media standards are written to keep free silica out of both.

For a machined aluminum part, the decision usually runs one way. A cosmetic housing, an enclosure, or any part where the dimensions matter goes to bead blasting. A part that needs a coating stripped, corrosion removed, or a paint-ready profile goes to aluminum oxide, accepting that it cuts. The two are not competitors for the same job so much as tools for different steps, and some parts see both: an aluminum oxide pass to clean or profile, then a glass bead pass for the final even look.

EPOC CRAFTER engineering note: We see this go wrong on thin-wall aluminum parts sent for sandblasting with no media called out. Blasted with coarse aluminum oxide at pressure, a thin wall can bow and a bearing bore can go out of round, and the part passes a quick visual while failing on the CMM. On soft aluminum that has to hold size, the safe default is glass bead unless there is a specific reason, like coating removal, to cut. Naming the media on the drawing settles it before the cabinet door closes.

6. What the media standards do not control

Everything up to here used MIL-PRF-9954D, ISO 11126-7, and ISO 11124-3 to pin down the media. This section marks the line those standards stop at. All three specify the abrasive as supplied. None of them specifies how you blast or what surface you end up with. Reading a final Ra or a matte level out of a media spec is the most common way blasting requirements go wrong on a drawing.

None of the three standards sets blast pressure, nozzle diameter, nozzle angle, standoff distance, abrasive flow rate, dwell time, number of passes, final Ra or Rz on the part, matte level, gloss, final color, or compatibility with a later anodize step.

MIL-PRF-9954D goes as far as naming the equipment type, pressure or suction blasting, and the intended uses, cleaning, peening, polishing, finishing. It stops there. It gives no pressure, no angle, no distance, no Ra. ISO 11126-7 and ISO 11124-3 do not even go that far on process; they define the abrasive and its test methods and leave the blasting operation outside their scope. So a certified media tells you the beads are round soda-lime glass of a known size and cleanliness. It tells you nothing about the finish, because the finish is made by the process, not bought with the media.

The surface result comes from variables the operator and the shop control: the pressure at the nozzle, the standoff distance, the angle, how long each area is worked, how many passes, and whether the media is fresh or worn. Change the pressure on the same MIL #10 bead and the Ra moves. Run the same beads until they fracture and the finish drifts. This is why a media grade cannot carry an Ra value, and why the honest place to set a roughness target is a first-article coupon in the actual media at the actual pressure, cross-checked against the Ra values each process delivers, checked instead of assumed from the bead size.

There is real, measurable data on what blasting does to aluminum, but it comes from process trials, not from the media specs. On additively manufactured aluminum, for one documented case, glass bead or aluminum oxide blasting brings surface roughness down from roughly Ra 6 to 15 um as-printed to about Ra 3 to 6 um without changing dimensions. That number is a measured process outcome on a specific substrate and setup, recorded on EPOC CRAFTER metal 3D printing work; it is not a value any of the three media standards guarantees, and it does not transfer unchanged to a milled 6061 face at a different pressure.

EPOC CRAFTER engineering note: On a drawing, we treat any Ra, matte level, or color target as a process requirement to confirm, and the media callout as a separate line that fixes what abrasive we buy. When a customer writes both on the same drawing, the two get inspected differently: the media by certification to the spec, the finish by a coupon or boundary sample. Keeping them separate is what makes a blasted finish repeatable batch to batch instead of a surprise each run.

7. Blasting before anodizing aluminum

Most bead-blasted aluminum parts are headed for anodizing, and the blast step decides how the anodize reads. At this point the media choice, the surface it leaves, and the color result all connect, and the blast stops being cosmetic and starts driving a downstream spec. Two things move: the appearance the anodize takes on, and the dimensions the film grows onto.

Bead blasting before anodize gives an even matte base that the oxide film follows. Because glass bead keeps the base color and leaves a uniform texture, the anodized surface reads consistent instead of showing the shade stripes and concentric rings that a milled or bored face carries into the anodize. A blasted matte is also its own visual reference: the texture changes how color is perceived independent of dye, so a bead-blasted anodized part and a machined-then-anodized part will not match even at the same film thickness and dye. A bead-blast finish gets specified as its own reference standard, not compared to a machined one.

The surface roughness left by the blast drives how tightly the anodize color can be held. On 6061, published EPOC CRAFTER anodizing data sets the practical thresholds: an Ra of 0.8 um or lower gives the most predictable color, matching a reference coupon within Delta-E 2; Ra 1.6 um is the ceiling for a Delta-E 2 target; and above Ra 3.2 um the surface cannot hold a tight color spec at all, because roughness scatters dye uptake and shifts the perceived color. The full relationship between surface roughness, film thickness, and anodized color on 6061 is a process result measured on real parts, not something the blasting media standard sets. The media gets the surface even; the Ra it lands at, confirmed by measurement, is what the color spec keys to.

Dimensions move too, in two places. Aluminum oxide blasting cuts and can shift a feature before anodize even starts, which is a reason to keep it off toleranced faces. Then the anodize film itself grows on and into the surface: MIL-A-8625F puts Type II film at 0.00007 to 0.0010 in and Type III at 0.0005 to 0.0045 in, with about 0.002 in as the Type III default, so a bore or a mating face has to be machined with that growth accounted for. The sequence and the allowances for machining 6061 for anodize sit alongside the blast decision, because the pre-anodize surface prep and the pre-anodize dimensions are set on the same drawing.

Masking ties the two together. Any face that carries a dimensional or color tolerance, plus sealing surfaces, O-ring grooves, and threads, gets masked before the blast so the media does not open or dull it, and often stays masked or gets re-masked through anodize. The prep you pick eats into size, so the drawing has to state the pre-anodize surface finish and its Ra range on the same sheet as the anodize callout, or the shop is guessing at which surface the color spec was written against.

EPOC CRAFTER engineering note: On consumer electronics housings we run bead-blast plus Type II anodize as a paired step and treat the blasted texture as the color reference, checked under raking light, not against a machined coupon. When a customer sends an anodize color target without stating the pre-anodize finish, we ask for it before quoting, because the same dye and thickness over a blasted surface and over a machined surface land at different Delta-E. Settling the blast finish first is what makes the anodize color repeatable.

8. Specifying bead blasting on an aluminum drawing

A blasting note that a shop can build to has four parts: the media, the grade, the finish target, and the masking. Leaving any one of them to the shop’s default is where blasted parts come back wrong. The media standards from Sections 2 through 6 give the vocabulary for the first two; the finish and masking are yours to set on the drawing.

Call out the media and grade explicitly. Bead blast alone lets the shop pick anything from a fine glass bead to a coarse aluminum oxide, which are two different surfaces. A complete media line names the abrasive, the grade, and where relevant the spec, such as glass bead in a fine grade or a specific MIL size. If the finish has to repeat across batches, the media callout is what holds it steady, because a shop that switches from glass bead to aluminum oxide between runs changes the look even with everything else equal.

Set the finish as a separate target, not as a number bolted to the grade. Because a media grade does not carry an Ra, the reliable ways to specify the look are a boundary sample, high-resolution reference photos, or an Ra range the shop confirms it can hold with the named media through a first-article coupon. One practical ceiling is worth knowing: holding a blasted surface below about 32 uin Ra (0.8 um) is hard, and specifying smoother than that on a blasted face usually means masking that face instead and finishing it another way. A tight roughness callout and a blast finish on the same surface work against each other.

Mask the features that a blast would damage. Sealing surfaces, O-ring grooves, and threads, especially fine-pitch threads, should carry a masking note so the media does not round the crests or open the groove. Any face with a dimensional tolerance that the blast could move belongs on the mask list too. Masking adds labor and cost, so it is worth marking only the features that need it instead of blanket-masking, and the drawing note should say which surfaces to protect so the shop is not left to guess. How the blasting note fits the rest of the drawing’s tolerance callouts matters, because the masked-off toleranced features still have to be dimensioned to the standard the rest of the print uses.

A workable drawing note for a cosmetic aluminum part reads roughly:

Bead blast all external surfaces with fine-grade glass bead media. Target finish per boundary sample or shop-confirmed Ra range. Mask sealing faces, O-ring grooves, and tapped holes prior to blasting. Do not blast surfaces with Ra callouts below 32 uin.

That note fixes the media, hands the appearance to a sample, and protects the features that a blast would otherwise ruin. It is the difference between a finish the shop can quote and hold, and a bead blast that comes back as a surprise. For a part that will also be anodized, the pre-anodize surface finish and its Ra range go on the same sheet as the anodize callout, following the sequence in Section 7, so the whole finishing route is specified in one place. When the finishing spec is complete, uploading the part for a CNC machining and finishing quote gives the shop everything it needs to price the blast, the masking, and any anodize together instead of coming back with questions.

9.Frequently asked questions

Can you bead blast aluminum?

Yes, and it is the standard cosmetic finish for machined aluminum. Glass bead is the usual media because it is spherical and low density, so it evens out tool marks and leaves a matte or satin surface while keeping the base color and holding dimensions on soft 6061 and 7075. Harder or coarser media cuts aluminum instead of finishing it, so the media choice is what makes the process safe on soft parts.

Is bead blasting better than sandblasting for aluminum?

For a cosmetic aluminum part that has to keep its dimensions, yes. Bead blasting with glass bead peens and brightens with very little material removal. Sandblasting with aluminum oxide cuts and etches, which strips coatings and leaves a paint profile but can move a tolerance and dull the surface. They are built for different jobs: bead blast to finish, aluminum oxide to strip or profile. Some parts get both, an oxide pass to clean followed by a glass bead pass for the final look.

What Ra does bead blasting produce on aluminum?

There is no fixed Ra for a given bead size, because no media standard maps a grade to a roughness. The result depends on the media, blast pressure, standoff distance, dwell time, number of passes, and whether the media is fresh or worn. As a direction, finer beads trend smoother and coarser beads leave more texture, but the actual Ra has to be confirmed on a first-article coupon in the real media at the real pressure. Holding a blasted surface below about 32 uin Ra (0.8 um) is difficult and usually calls for masking instead.

Can bead blasting damage an aluminum part?

It can, if the media or pressure is wrong for the part. Too much pressure or a hard, coarse media can pit or dish a surface, bow a thin wall, round thread crests, or embed media into the aluminum. The controls are choosing glass bead for soft cosmetic parts, masking sealing faces and threads, and keeping steel media off the aluminum line so iron fines do not transfer and become corrosion sites after the part is in service.

Is glass bead blasting safe compared with silica sand?

Glass bead avoids the respirable crystalline silica hazard that traditional silica sand carries, which is a main reason the industry moved away from sand. MIL-PRF-9954D caps crystalline silica in glass bead below 0.1% by weight, and ISO 11126-7 requires fused aluminum oxide to contain no free silica. Any blasting still needs proper containment, dust extraction, and operator protection, but the media itself is specified to keep free silica out.

Can you bead blast stainless steel with the same setup?

Stainless steel can be glass bead blasted for cleaning and a satin finish, but the media has to be kept separate from what touches aluminum. Media that has contacted steel or stainless transfers iron onto aluminum, which causes corrosion or plating and anodize problems later. Cross-contamination between metal families is the reason shops run separate cabinets or media charges instead of a single shared setup.

10.Where this leaves your drawing

Name the media, set the finish with a sample or a shop-confirmed Ra range, and mask the features a blast would ruin. On aluminum that means glass bead for a cosmetic surface, aluminum oxide only when you need to strip or profile, and steel media kept off the soft parts entirely. The three media standards fix what you buy; the process and a first coupon fix what you get. Specify both, on the same drawing as any anodize callout, and the finish repeats batch to batch.

Send the CAD and the finishing spec together and EPOC CRAFTER returns a quote in 12 hours with DFM feedback on the blast, the masking, and any anodizing or surface finishing in one response.

Related resources

• Related Article: Machining 6061 for anodize. How much to oversize features and what Ra to leave before an anodize step, including masking decisions.
• Related Article: Anodizing thickness, color, and corrosion on 6061. How pre-anodize Ra drives color repeatability and Delta-E targets.
• Related Reference: Surface roughness chart for CNC parts. The Ra and Rz each process delivers, for setting a finish target.
• Related Capability: Surface finishing. Blasting, anodizing, plating, and coating options with color-matching to Delta-E 2 or better.
• Related Capability: CNC machining. The aluminum machining that comes before the finish, in 6061, 7075, and more.