This article is part of the CNC Machining Materials Guide: Metals, Plastics & Superalloys on CNX Precision.
Magnesium AZ31 machining delivers the best strength-to-weight ratio of any common structural metal, which makes it a favorite for aerospace and portable electronics. It also creates hazards that ordinary metals do not. Fine magnesium chips and dust can ignite, and the cooling strategy is not optional. In this guide, you will learn how to machine AZ31 safely and efficiently, including cutting parameters, tooling, chip handling, and fire prevention, so you can produce lightweight parts without shop-floor risk.
Why Magnesium AZ31 Machining Asks for Special Care
Magnesium AZ31 is the lightest common structural alloy, with a density roughly one-third lower than aluminum. The designation AZ31 refers to its aluminum and zinc content: about three percent aluminum and one percent zinc, with manganese added in small amounts. That light weight, combined with high specific strength and excellent damping, explains why engineers keep choosing it.
The danger is real, however. Magnesium chips ignite at relatively low temperatures. Fine turnings, dust, and broken-off chip fragments burn brightly and are hard to extinguish. Common extinguishing methods can make things worse. Water reacts with hot magnesium and releases hydrogen, adding an explosion risk. Every machine setup, tool choice, and cleanup routine must account for this hazard from the start.
Strength, Weight, and Damping: The AZ31 Advantage
AZ31 offers an exceptional strength-to-weight ratio. Components machined from it can be lighter than aluminum equivalents while carrying similar loads. Magnesium also absorbs vibration better than many metals, which matters for housings that enclose rotating machinery. The alloy holds good dimensional stability for precision parts, and it machines with low cutting forces. These properties create real engineering wins.
When every gram counts in flight hardware, or when a handheld device must survive constant handling, AZ31 earns its place. The material has drawbacks, chiefly corrosion susceptibility and fire risk. With proper design, coating, and shop discipline, both are manageable.
Machining economics reinforce the choice. Because AZ31 cuts with low forces, cycle times can be shorter and tool life longer than on comparable steel parts. The energy savings grow with production volume. For a supplier, shorter cycles make quotes competitive, and for the buyer, lighter parts shrink shipping and assembly costs.
The Core Cutting Rules for AZ31
Good magnesium AZ31 machining follows a consistent set of rules. Use sharp tools with high rake angles. Dull edges push instead of cut, generating heat and promoting chip welding. Run high cutting speeds with moderate-to-large feed rates so the insert removes a thick chip. Thick chips carry heat away quickly and are less likely to ignite than thin, fragile swarf.
Keep the tool in constant contact and avoid rubbing, which creates the microscopic hot points where fires begin. Choose positive-rake inserts designed for aluminum or magnesium. Machine with a magnesium-safe mineral oil mist, or run dry with compressed air. Avoid water-based coolants because water can react with magnesium chips and release hydrogen. Discipline on the cutting parameters separates safe shops from risky ones.
Workholding and setup deserve equal attention. Magnesium parts are light and can vibrate if clamped poorly, so use rigid fixtures and full support on thin sections. Remove components promptly after machining and let them cool away from accumulated chips. These simple practices keep the job predictable from the first cut to the final deburr.
Fire Prevention and Housekeeping That Work
Fire safety begins at the machine. Use enclosures, guards, and mist extraction to keep chips near the cutting zone and under control. Remove chips often and never let them pile up. Use a vacuum rated for flammable dust, and keep collection containers grounded to prevent static discharge.
Store chips in clearly labeled, sealed metal containers away from ignition sources. Never mix magnesium chips with other metal chips, because certain mixtures react violently. Keep a Class D fire extinguisher and dry sand or powder near the machine. Never use water, foam, or ordinary dry-chemical extinguishers on a magnesium fire.
Give the same care to the cutting fluid. Use only magnesium-safe mineral oil formulations, monitor the fluid regularly, and clean chips from sumps and filters on a schedule. Train operators on ignition signs and emergency response, and inspect extinguishers every shift. Good housekeeping is the cheapest insurance in any magnesium AZ31 machining operation.
Personal protection completes the safety loop. Operators should wear flame-resistant aprons and eye protection, and the shop should post printed procedures for chip removal, storage, and fire response near every magnesium machine. Written rules reduce the chance that a rushed operator skips a safety step.
Finishing and Corrosion Protection for AZ31 Parts
Raw AZ31 is reactive and corrosion-prone, so finished parts need protection. Common treatments include chromate or chrome-free conversion coatings, magnesium anodizing methods, and powder coat or paint for exterior surfaces. Pair the coating with the service environment; marine and high-humidity applications demand the heaviest protection.
Handle parts carefully after machining. Keep magnesium parts separate from steel and other metals during storage and shipping to avoid galvanic corrosion. Include drainage and venting features in housings where moisture can collect. State the coating requirement on your drawing, and let your CNC supplier verify the finish matches the specification.
Design for finishing from the start. Round internal corners, avoid deep blind pockets that trap chips, and specify edge breaks that let coatings cover evenly. Small geometry choices make AZ31 parts safer to machine and easier to protect.
Applications Across Aerospace and Electronics
Magnesium AZ31 machining shows up wherever weight savings matter most. Aerospace teams machine AZ31 into brackets, housings, and structural supports for aircraft, helicopters, and satellites. Electronics makers use it for laptop frames, tablet chassis, and camera housings, where rigidity and low weight boost both performance and portability.
Power tool housings, drone frames, and automotive braces also benefit from AZ31’s balance of properties. When designers select AZ31, the machining partner must pair the metal’s benefits with disciplined process control. A supplier that demonstrates safe, repeatable magnesium AZ31 machining practices brings genuine value to these projects.
Coating selection ties directly to the part’s final service. Aerospace parts often carry conversion coating plus primer, while consumer housings use decorative powder coat. Discuss the finish with your supplier before production begins, and confirm that the coating system is approved for magnesium alloys.
Is magnesium AZ31 flammable during machining?
Yes. Fine AZ31 chips and dust can ignite when cutting temperatures are high enough. Sharp tooling, thick chips, and controlled cooling reduce the risk. Class D extinguishers and dry sand are essential for responding to any fire that does occur.
Can you use water-based coolant for magnesium AZ31 machining?
Standard practice avoids water-based coolants because water reacts with magnesium chips and can release hydrogen gas. Most shops use a magnesium-safe mineral oil mist or run dry with compressed air, keeping temperatures low and avoiding the reaction risk.
What products are commonly machined from magnesium AZ31?
Common parts include aerospace brackets and housings, electronics casings, laptop and tablet frames, power tool housings, and drone structural components. These applications benefit from AZ31’s light weight, high specific strength, and good damping.
For related information, see our guide to cnc machining magnesium and cnc machining service and 5-axis cnc machining, and cnc machining tolerances.