Not every precision part should be bead blasted — and determining suitability early in design prevents costly tolerance issues and production delays. With decades of CNC experience across aerospace, medical, and audio applications, we’ve learned that the wrong finishing choice can turn perfectly machined components into expensive scrap metal.
Skip bead blasting for parts with tight tolerances (±0.01 mm or tighter) where the 0.005–0.025 mm material removal creates risk. Also, if your product has tight tolerances, the material removal can cause dimensional issues, particularly on walls below 1.5 mm thickness that risk deflection and warping from blast pressure. The blasting process can also damage materials with complex geometries or thin walls.
Learn which geometries suit bead blasting, when masking or alternate finishes are needed, and how material choice impacts results—based on real production runs.
Table of Contents
Will bead blasting alter my part's critical dimensions and tolerances?
Bead blasting removes 0.005–0.025 mm of material uniformly across all surfaces, which makes any tolerance tighter than ±0.02 mm risky. For features requiring ±0.01 mm or tighter, consider the material removal in your tolerance stackup or mask critical surfaces during processing. This isn’t theoretical — on precision aluminum housings with ±0.02 mm tolerances, we consistently see 0.008–0.012 mm material loss that must be accounted for during machining.
Quick Tolerance Check:
- ±0.005 mm or tighter → Always mask or avoid bead blasting
- ±0.01-0.02 mm → Proceed with caution, adjust nominal dimensions
- ±0.03 mm or looser → Safe for bead blasting without adjustment
30-Second Drawing Review:
- Highlight all tolerances ±0.02 mm or tighter
- Identify these red flags: press-fit holes, bearing bores, threaded features, gasket grooves, seal surfaces
- If >50% of tight tolerances are functional → Consider alternative finishing
Here’s what happens in practice: an H7 bearing bore specified at 10.000 mm (+0.015/-0.000 mm) becomes 10.010-10.025 mm after blasting, turning a precise transition fit into loose clearance. We learned this during an audio equipment project where faceplate mounting holes grew from 6.2 mm to 6.35 mm, making screws loose in production parts.
Design Takeaway: Review your drawings right now — any dimensions marked ±0.01 mm or tighter need attention before production. Build the 0.010–0.020 mm material removal into your nominal dimensions, or specify masking for critical features. The cost of re-machining failed parts always exceeds proper planning expenses.
Is my chosen material suitable for bead blasting without damage?
Aluminum alloys (6061, 7075) respond excellently to bead blasting, while stainless steel and mild steel show good results. Avoid bead blasting on soft materials like brass, copper, or thin plastic components that can deform under media impact. Material compatibility follows established hardness thresholds per ASTM E18 Rockwell testing. Aluminum alloys with hardness ranges 25-87 HRB demonstrate optimal bead blasting response without surface embedding.
Material Compatibility Quick Check:
- Safe Materials: Aluminum (6061, 7075), stainless steel (304/316), mild steel, titanium
- Risky Materials: Brass, copper, bronze, soft plastics, thin-walled components
- Never Blast: Glass, ceramics, mirrors, optics
Abrasive action can harm soft materials like copper, bronze, or brass, while brittle materials such as glass or ceramics may shatter or crack. Materials below 35 HRB (brass, copper per ASTM B36/B152) show surface deformation and media embedding under standard glass bead impact. We’ve seen brass fittings develop surface cratering and copper heat sinks with embedded glass particles that required complete part replacement.
Already Committed to Risky Materials? Design Alternatives:
- Copper parts requiring texture → Specify chemical etching for consistent Ra 0.8-1.5 μm finish
- Brass fittings needing grip → Mechanical brushing creates directional texture without embedding
- Thin-wall components → Vapor polishing or as-machined finish avoids deflection risk
Stainless steel grades 304/316 at 70-85 HRB require ceramic media and higher pressures due to work hardening characteristics defined in ASTM A240 specifications. Industry surface preparation guidelines recommend minimum 2:1 hardness ratios between media and substrate to prevent embedding while achieving effective texturing.
Design Takeaway: Stick with aluminum alloys for predictable bead blasting results. If your design requires soft metals for specific properties (conductivity, corrosion resistance), choose alternative texturing methods early in the design phase to avoid costly redesigns when manufacturing issues surface.
What kind of surface texture will bead blasting create?
Bead blasting produces Ra surface finishes between 1.6–6.3 μm with uniform matte texture. Glass beads achieve Ra 1.6–3.2 μm for cosmetic applications, while ceramic beads create Ra 3.2–6.3 μm textures for improved paint adhesion. When using finer grades, the blasted surface will appear bright with a matte or satin-like texture due to how light reflects off the dimpled surface.
Texture Selection Decision Tree:
- Will users touch this surface daily? → Ra 1.6-2.5 μm (smooth, premium feel)
- Does it need paint/coating adhesion? → Ra 4.0-6.3 μm (creates mechanical bond)
- Is it purely functional/hidden? → Ra 3.2-4.0 μm (cost-effective, durable)
Application-Specific Texture Selection:
- Consumer electronics housings → Ra 1.6-2.5 μm (premium feel, hides fingerprints)
- Industrial enclosures → Ra 3.2-4.0 μm (durable, cost-effective)
- Paint preparation surfaces → Ra 4.0-6.3 μm (improves coating adhesion)
When a piece of rounded media impacts a part’s surface, it produces a tiny dimple at the impact location. As the process continues, thousands of these dimples consistently form over the surface. We recommend limiting surface roughness to no lower than 32 μin Ra when you need a smooth bead blasted part. Going finer than Ra 0.8 μm typically requires masking or alternative finishing methods.
The key advantage: The bead blast surface finish gives you a non-directional smooth and textured surface that is also aesthetically pleasing. Unlike machining marks that create directional scratches, bead blasting produces uniform texture that looks consistent from all viewing angles — critical for consumer-facing parts.
Design Takeaway: Choose texture based on function first, aesthetics second. User-contact surfaces justify the cost of finer finishes (Ra 1.6-2.5 μm), while hidden functional parts can use coarser, more economical textures (Ra 3.2-4.0 μm) without compromising performance.
Bead blasting precision parts?
We ensure surface finish meets dimensional needs • Confirm if blasting suits your tolerances
Could bead blasting weaken fine features or edges in my design?
Walls below 1.5 mm thickness risk deflection and warping from blast pressure, while sharp internal corners under 0.5 mm radius create stress risers where bead impact can initiate micro-cracks. We recommend minimum 0.5 mm radii on all internal corners planned for bead blasting. During a medical device project, we watched 1.2 mm aluminum walls permanently bow outward 0.2 mm from peening stress.
Design Risk Assessment:
- High Risk: Walls <1.5 mm, internal corners <0.5 mm radius, deep pockets >3:1 depth-to-width ratio
- Medium Risk: Fine threads, thin flanges, unsupported overhangs
- Safe Features: Thick walls >2.0 mm, generous radii >1.0 mm, accessible surfaces
Avoid deep narrow pockets (deeper than 3x width), sharp internal corners under 0.5 mm radius, and thin walls below 1.5 mm thickness when designing for bead blasting. The pocket geometry issue is pure physics — glass beads bounce off edges but can’t reach deep corners effectively. We recently processed aluminum audio faceplates where 15 mm deep display cutouts with 4 mm openings (3.75 ratio) left the bottom shiny with visible tool marks while everything else turned uniformly matte.
Stuck with Risky Features? Design Workarounds:
- Can’t thicken walls? → Add internal ribs for support during blasting, or consider fixture-supported blasting
- Sharp corners required for function? → Accept mixed finish and document it as acceptable
- Deep pockets unavoidable? → Specify hand-finishing for deep areas, or accept non-uniform texture
CAD Validation Steps You Can Do Right Now:
- Thickness Analysis: Select all faces, check minimum thickness on flat sections >20 mm square
- Radius Measurement: Use radius tool on all internal corners, especially L-shapes and brackets
- Pocket Calculator: Depth ÷ width for all openings — flag anything >3.0 as risk
Sharp internal corners create stress risers where bead impact can initiate micro-cracks, particularly in heat-treated aluminum. Complex undercuts or re-entrant angles prevent uniform media flow, creating “shadow zones” with inconsistent texture that require secondary hand-finishing operations.
Design Takeaway: Address risky features during design phase with either geometry changes or planned workarounds. Discovering finish problems during production leads to expensive part redesigns or acceptance of mixed surface quality that affects product perception.
Which features should be masked to avoid unwanted blasting?
Critical surfaces like bearing bores, threaded holes, or mating faces typically require masking during bead blasting to maintain dimensional accuracy. Alternatively, leave 0.015 mm stock on these features and finish-machine after blasting. Examples of these features are sealing surfaces and o-ring grooves.
Quick Mask/No-Mask Decision:
- Tolerance ≤±0.02mm? → Mask it
- Will you inspect this feature? → Mask it
- Cosmetic threads users see? → Mask it
- Hidden through-holes >6mm? → Safe to blast
What Requires Masking:
- Threaded features: All internal threads, especially fine pitch <M3 or #6-32
- Precision fits: Bearing bores, shaft journals, press-fit holes
- Sealing surfaces: O-ring grooves, gasket faces, mating surfaces
- Blind holes <6 mm diameter: Media contamination risk, difficult to clean afterward
How to Specify Masking:
- Drawing callouts: “MASK M4 THREADS AND 10mm BORE” with leader lines to specific features
- Material specification: Silicone plugs for holes (oversized by 0.030″), high-temp masking tape for complex shapes
- General note: “BEAD BLAST ALL SURFACES EXCEPT AS NOTED” prevents confusion
- CAD highlighting: Send 3D model with masking areas clearly marked in different color
Although most shops already do this per shop practice, we recommend adding masking requirements for threaded features, especially for small or fine pitch threads. From manufacturing medical device components, we’ve learned that blind holes under 6 mm diameter trap media particles that become nearly impossible to remove completely.
Complex masking significantly impacts costs and lead times. Simple masking operations typically add 15-25% to base finishing costs, while parts requiring extensive masking of multiple complex features can increase costs by 30-50%. Complex parts requiring extensive masking can cost 20-30% more. Lead times also extend by 1-2 additional days for masking setup and post-blast inspection verification.
Design Takeaway: Plan masking areas during design, not production. Consider whether alternative geometries (larger holes, external threads, looser tolerances) could eliminate masking needs entirely and reduce finishing costs by 20-30%.
When should bead blasting occur in my production sequence?
Schedule bead blasting after all machining is complete but before anodizing. The process removes roughly 0.01 mm of material, so any tight-tolerance features machined afterward will be undersized.
From coordinating hundreds of multi-vendor projects, timing is everything. Ship parts to your finisher within 48 hours of machining completion – aluminum oxidizes quickly and creates adhesion problems. We’ve seen projects delayed weeks because parts sat too long between operations.
Practical Production Sequence:
- Complete all machining (drilling, tapping, milling)
- Quality inspection (verify dimensions before blasting)
- Immediate packaging (clean parts, no handling marks)
- Bead blasting (glass beads at 60-80 PSI)
- Post-blast cleaning (remove embedded media)
- Anodizing within 24-48 hours
Multi-Vendor Coordination Strategy: Include witness samples with every shipment for quality verification. Specify “CLEAN GLASS BEAD MEDIA ONLY” on your purchase orders – contaminated media from previous steel jobs embeds iron particles that show as dark spots after anodizing.
For complex geometries, plan fixture points that won’t interfere with blast coverage. Internal features smaller than 6 mm diameter typically can’t be reached effectively.
Timeline Reality Check: Add 3-5 days to your schedule for blasting and coordination. Rush jobs cost 50-100% more and often produce inconsistent results.
Design Takeaway: Lock in your vendor sequence during design review. Specify “BEAD BLAST AFTER FINAL MACHINING” on drawings. Changes after tooling setup typically cost 2-3x more than proper planning.
How does bead blasting influence coating or anodizing quality?
Bead blasting creates uniform Ra 2.0-2.5 μm surface texture that eliminates machining marks and dramatically improves both coating adhesion and anodizing color consistency.
The difference is immediately visible. Without bead blasting, anodized parts show streaky, uneven color from directional tool marks. With proper glass bead preparation, you get consistent matte texture and uniform color across the entire surface.
Measured Performance Improvements: For paint systems, we routinely see 40-60% better adhesion on bead-blasted surfaces using standard cross-hatch testing. The micro-texture provides mechanical anchor points that smooth machined surfaces simply can’t match.
Anodizing Quality Benefits: Glass bead texture eliminates the “zebra striping” effect common on machined surfaces. The Ra 2.0-2.5 μm profile creates optimal base for Type II anodizing with consistent thickness and appearance. Medical device housings especially benefit from this uniformity for sealing applications.
When Bead Blasting Doesn’t Help: For maximum structural paint adhesion (aerospace, marine), aluminum oxide blasting creates deeper Ra 3-5 μm anchor profile. Glass beads work great for cosmetic anodizing but may be insufficient for critical load-bearing painted joints.
Quality Verification Approach: Plan first-article cross-hatch adhesion testing before production commitment. Specify Ra 2.0-2.5 μm surface finish requirements on coating purchase orders. Most coating failures trace back to inadequate surface preparation, not coating defects.
Design Takeaway: Specify bead blasting for any anodized cosmetic surfaces. For structural painted assemblies, evaluate whether more aggressive surface preparation provides better long-term reliability.
How much cost does bead blasting add to my part?
Bead blasting typically adds $2-8 per part for small aluminum components, but the setup costs and minimum charges often matter more than per-part pricing. Most finishing shops charge by time or have minimum batch charges rather than strict per-piece pricing.
Choose bead blasting for consumer-facing parts, anodized surfaces where appearance consistency matters, or when you need uniform texture for coating adhesion. Skip it for internal components, painted surfaces, or high-volume production where appearance variation is acceptable.
From coordinating finishing projects at Okdor, the real cost driver is often the minimum charge structure. Small prototype batches of 5-20 parts typically hit minimum charges of $75-150, making per-part costs seem high. Production runs over 100 parts often see costs drop to $2-5 per part depending on size and complexity.
Setup costs include fixture preparation for odd-shaped parts and masking for selective blasting. Simple brackets and faceplates process quickly, while complex housings with internal features requiring masking take longer and cost more.
The smart money focuses on total project value rather than just blasting fees. We’ve seen customers spend an extra $200 on bead blasting for 100 parts but save $800 in rework from poor anodizing quality on brushed surfaces.
Lead time averages 2-3 days for standard work, longer during busy periods. Rush jobs typically double pricing.
Design Takeaway: Budget $3-6 per part for planning purposes, but get actual quotes from local vendors since pricing structures vary significantly. The investment typically pays for itself through consistent finishing results.
Is bead blasting the best finishing option compared to others?
For anodized parts requiring uniform appearance, bead blasting outperforms alternatives, but many applications succeed with simpler finishes. The performance difference becomes obvious on parts larger than credit-card size where uneven anodizing creates visible quality issues.
Glass bead blasting creates Ra 1.6-2.4 μm uniform texture eliminating directional grain patterns Pricing. Bead blasting before anodizing significantly improves adhesion and creates more uniform finish appearance. Consumer electronics and audio equipment especially benefit because directional tool marks become obvious under certain lighting.
Glass bead blasting is not a great preparatory process for painting, while aluminum oxide blasting makes surfaces more adhesive and receptive to further finishes. Industrial applications often perform better with brushed finishes costing less, especially when appearance uniformity matters less than cost.
Parts with critical tolerances sometimes avoid bead blasting because the process removes 0.005-0.015 mm of material Pricing. High-volume production occasionally accepts anodizing variation to reduce per-part costs.
Test actual parts before production commitment. Request samples with different finishes from your anodizer – quality differences are immediately visible under normal lighting. We’ve seen projects switch finishing methods after seeing real results, adding time to timeline but preventing costly field quality issues.
Design Takeaway: Match finishing performance to customer expectations and functional requirements. Consumer products usually justify the investment, while industrial applications often succeed with cost-effective alternatives.
Conclusion
Bead blasting delivers consistent anodized finishes for consumer products but isn’t necessary for every application. Match your surface preparation to functional requirements and budget constraints. For precision aluminum components requiring uniform appearance, the investment typically justifies itself through reduced quality issues. Contact us to explore bead blasting and manufacturing solutions tailored to your product requirements.
Frequently Ask Questions
Yes, but mask all threaded features before blasting. Media can embed in thread roots and cause assembly problems. Use rubber plugs or tape masking for through-holes, and specify “MASK ALL TAPPED HOLES” on your drawings. The masking adds $0.25-0.75 per part but prevents costly thread damage.
For most applications, maintain tolerances no tighter than ±0.025 mm on blasted surfaces. The process removes 0.005-0.015 mm of material, so critical dimensions under ±0.02 mm should be masked or machined after blasting. We recommend compensating by adding 0.01 mm to your CAD dimensions before machining if the entire surface will be blasted.
For maximum paint adhesion on structural components, aluminum oxide creates a better anchor profile (Ra 2.4-3.2 μm) than glass beads (Ra 1.6-2.4 μm). However, glass beads work fine for cosmetic painted parts and provide smoother feel for consumer products. Test both options on samples before production commitment.
Request first-article cross-hatch adhesion testing per ASTM D3359 before production commitment. Properly prepared surfaces typically show 90%+ adhesion pass rates versus 60-70% on as-machined parts. Also specify surface roughness verification to Ra 1.6-2.4 μm using portable roughness testers.
Work with your finisher to establish witness samples and quality standards upfront. Uneven blasting from manual techniques often causes rejection – specify consistent pressure and coverage requirements. Most quality issues trace back to contaminated media or insufficient cleaning between different materials.
Ship parts immediately after machining in sealed containers to prevent oxidation. Specify “CLEAN GLASS BEAD MEDIA ONLY” on purchase orders – contaminated media from previous steel jobs embeds iron particles that show as dark spots after anodizing. Plan maximum 48 hours between machining and blasting for best results.
