Mirka AROS-B 325 – The Cordless Random Orbital Sander for Maximum Mobility in Automotive Applications
Updated: March 2025 · Reading time: approx. 7 min.
Why Go Cordless? – The Promise of the AROS-B 325
In today's body and paint shops, every second counts. Air hoses running across the workshop floor and heavy cable reels waste time, restrict freedom of movement, and increase the risk of accidents. Mirka addresses this everyday challenge with the AROS-B 325: a battery-powered random orbital sander developed specifically for spot repairs, body-in-white (BIW) sanding, and post-paint finishing steps.
Lightweight, low-vibration, and fully integrated into Mirka's 12 V battery ecosystem, the AROS-B 325 bridges the gap between a basic denibber and a full-sized grinder – delivering controlled material removal that makes precise work possible.
Product Overview: AROS-B 325 vs. AROS-B 350 Comparison
All values according to manufacturer specifications (reference values, as of 03/2025).
| Feature | AROS-B 325 | AROS-B 350 |
|---|---|---|
| Orbit | 2.5 mm (3/32″) | 5 mm (3/16″) |
| Vibration Level | 1.6 m/s² | 2.5 m/s² |
| Weight | 0.88 kg | 0.88 kg |
| Noise Level (LpA) | 61 dB | 61 dB |
| Battery Voltage | max. 12 V DC | max. 12 V DC |
| Pad Diameter | 77 mm (3″) | 77 mm (3″) |
| Speed Range | 4,000–7,000 rpm | 4,000–7,000 rpm |
| Motor | Brushless 12 V | Brushless 12 V |
| Ideal Application | Fine sanding, spot repair, post-paint finishing | More aggressive sanding, primer preparation |
| Product Code | 8991153252 | 8991153502 |
| Included | Sold without battery and charger | |
Order the Mirka AROS-B 325 now at beschicht.com
Without battery & charger (compatible with all Mirka 12 V ecosystem batteries)
Buy Now – Mirka AROS-B 325Recommended Base Settings (Reference Values)
The following values are derived from manufacturer specifications and serve as a starting point. Individual workpiece conditions may require adjustments.
| Application | Speed (Reference) | Recommended Abrasive |
|---|---|---|
| Post-paint / clear coat fine sanding | 4,000–5,000 rpm | Abralon® P1000–P2000, Ø 77 mm |
| Primer / e-coat sanding (BIW) | 5,500–7,000 rpm | Mirka Galaxy / Iridium P150–P400, Ø 77 mm |
| Wet sanding / denibbing | 4,000–5,500 rpm | Abralon® J3 / Abralon® P800+, Ø 77 mm |
| Spot repair / small-area correction | 4,500–6,000 rpm | Iridium Soft / Abralon® P400–P800, Ø 77 mm |
* Reference values – please adjust to the material, paint build-up, and ambient temperature.
Pro Workflow: Spot Repair with the AROS-B 325 (6 Steps)
- Preparation & Battery Check: Insert the Mirka Intelligent Battery and check the charge level via the display or the myMirka app. Clean the work area and remove any sanding dust from previous steps.
- Select & Attach Abrasive: Choose the appropriate Abralon® or Iridium disc based on defect depth (inclusion, run, orange peel) and attach it to the 77 mm hook-and-loop pad. For wet sanding, lightly moisten the work surface.
- Set Speed: Start at approximately 4,000–5,000 rpm for clear coat corrections (reference value). Adjust speed using the +/– buttons on the tool; the myMirka app displays the current speed in real time.
- Sand – Controlled and Consistent: Place the sander flat on the surface and apply light, even pressure. Avoid circular hand movements; instead, work in straight, overlapping passes. The fine 2.5 mm orbit prevents deep scratch marks.
- Intermediate Check: Wipe away sanding dust (for wet sanding: rinse off), then inspect the area with raking light or an LED lamp. If needed, switch to a finer grit and repeat.
- Final Cleaning & Polishing: Remove all abrasive residue from the surface. Direct transition to the Mirka AROP-B 312 (compatible polisher) or ARP-B 300 for a high-gloss finish is possible – same battery platform, no system change required.
Troubleshooting: Common Issues & Solutions
- Check battery charge – below 20% capacity, throttle the tool or swap the battery.
- Is the battery properly seated? Inspect contacts for dirt and clean with a dry cloth.
- Overheat protection triggered: let the tool cool down for 10–15 minutes, then restart.
- Check that the abrasive disc is seated correctly – replace warped or damaged discs immediately.
- Inspect the hook-and-loop pad for wear and even adhesion; replace if necessary.
- Bearing or motor noise: send the tool to Mirka Service (check warranty coverage).
- Reduce speed – excessive rpm on soft paint generates heat and scratches.
- Check pressure: use only the tool's own weight, no additional downward force.
- Work through grits progressively; do not skip more than one grade at a time.
- Clean the hook-and-loop pad and the back of the disc from dust and water – especially after wet sanding.
- Only use Mirka-compatible 77 mm abrasives with a hook-and-loop backing.
- Worn hook-and-loop pads significantly reduce adhesion – replace them in good time.
Maintenance & Care – 5 Key Points
- Clean the housing: After every shift, wipe off sanding dust and moisture residue with a dry or slightly damp cloth. The sealed housing protects against dirt and water ingress – avoid stressing the seals with aggressive cleaning agents.
- Inspect the hook-and-loop pad: Regularly check for wear, foreign particles, and detached hook fibres. A damaged pad leads to poor abrasive adhesion and uneven results.
- Store the battery: Keep the Mirka Intelligent Battery at 50–80% charge at room temperature (10–25 °C). Deep discharge and heat shorten battery life. Monitor charge status via the myMirka app.
- Clean battery contacts: If necessary, clean the contact surfaces between the battery and the tool with a dry brush – oxidised contacts can cause performance loss.
- Preventive inspection: Mirka recommends using the Preventive Maintenance programme at my.mirka.com. Tools can be registered there, service appointments scheduled, and repairs coordinated – including extended warranty (2+1 years when registered within 30 days of purchase).
FAQ – Frequently Asked Questions about the Mirka AROS-B 325
Which battery is compatible with the AROS-B 325?
The AROS-B 325 is compatible with the full Mirka 12 V battery range, including the Mirka Intelligent Batteries BPA 11125 (2.5 Ah) and BPA 11150 (5.0 Ah). These are charged using the BCA 108 charger (sold separately) with a quick-charge time of approximately 45 minutes. The sander is sold without battery and charger.
Can the AROS-B 325 be used for wet sanding?
Yes. Thanks to its fully sealed design, the AROS-B 325 is protected against both dust and water and is explicitly suited for wet sanding applications – such as post-paint sanding and denibbing. Abrasives like Abralon® or Abralon® J3 are particularly well suited for wet applications with the 77 mm pad.
What is the difference between the AROS-B 325 and AROS-B 350?
The only technical difference is the orbit size: the AROS-B 325 operates with a 2.5 mm orbit – ideal for fine detail work and finishing steps. The AROS-B 350 offers a 5 mm orbit for more aggressive material removal, for example during primer sanding. Weight, noise level, pad size, and battery compatibility are identical.
How long does a battery charge last when using the AROS-B 325?
The exact run time depends on battery capacity, speed setting, and applied pressure. The BPA 11150 (5.0 Ah) allows significantly longer uninterrupted sanding sessions than the BPA 11125 (2.5 Ah). For intensive shift work, a spare battery set is recommended to minimise downtime. The myMirka app displays the exact charge level of the Intelligent Battery.
Is the AROS-B 325 connected to the myMirka app?
Yes. The AROS-B 325 is fully compatible with the myMirka app (available on the App Store and Google Play). The app allows you to monitor speed settings, view operating data, and manage the tool within the Mirka ecosystem – including tool registration for warranty extension to 3 years (within 30 days of purchase).
Conclusion
The Mirka AROS-B 325 is a focused answer to the demands of modern automotive and body shops: compact, low-vibration, cordless, and seamlessly embedded in a proven battery ecosystem. With its 2.5 mm orbit, it covers precisely the range where fine sanding and surface correction require the most control – without the limitations of a corded tool. Those already using Mirka cordless polishers can step straight in; newcomers gain a future-proof platform for further cordless Mirka tools. A clear recommendation for professionals who refuse to compromise between mobility and quality.
Ready for more mobility in your workshop?
Order the Mirka AROS-B 325 now at beschicht.com – fast delivery, expert advice.
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