Does 7075 aluminum machine like 6061?
While the core techniques are similar, they are not identical. Many machinists, especially those experienced with harder materials, treat them similarly with success. However, 7075 is stronger and more abrasive, leading to faster tool wear if parameters aren’t adjusted. The most significant difference lies in its tendency for residual stress and distortion, which is a far greater concern in 7075-T6 than in 6061. So, while feeds and speeds may be in the same ballpark, the strategy for managing the workpiece and achieving final tolerances often requires more forethought with 7075.
What is the best SFM (Surface Feet per Minute) for machining 7075?
For carbide end mills and face mills, a range of 300-500 SFM is a strong starting point. For high-performance coated carbide tools, speeds at the upper end of this range or even slightly above are common. For drilling with carbide, similar speeds apply. When using HSS (High-Speed Steel) tools, speeds must be reduced significantly, typically to the 150-250 SFM range. The “best” SFM always depends on your specific tooling, machine rigidity, and operation—always consult your tooling manufacturer’s recommendations and be prepared to adjust based on chip formation and tool life.
Why is my 7075 part warping or distorting after machining?
This is almost always due to the release of residual stresses within the raw material stock (plate, bar, or forging). As you remove material, you disrupt the internal stress equilibrium, causing the part to bend or twist to find a new balance. To combat this, use the strategies outlined above: source stress-relieved stock (like T7351) for critical parts, employ symmetrical roughing, allow the part to relax (unclamp it) after bulk removal, and finish machine in a low-stress state. It’s a management problem, not an elimination problem.
Is 7075 aluminum gummy to machine?
This is a common point of confusion. The classic T6 temper should machine cleanly, producing small, broken chips. If you are experiencing a gummy, stringy chip and a poor surface finish, the most likely culprits are: 1) Using a feed rate that is too low, causing rubbing instead of shearing, or 2) Machining a softer temper like T7351 or O (annealed), which genuinely is more ductile. Increasing your feed rate per tooth is the first and most effective remedy.
What type of end mill is best for 7075?
Three-flute carbide end mills are widely considered the ideal choice for slotting and profiling in 7075. They provide an excellent balance of chip clearance and strength. For finishing, 2-flute or 3-flute tools with highly polished flutes and sharp cutting edges are preferred. The tool must be sharp—7075 is less forgiving of a slightly dull tool than 6061. Tools with specialized aluminum coatings (like ZrN) or uncoated, polished carbide help prevent material adhesion.
Can you weld 7075 aluminum?
Generally, no. 7075 is considered non-weldable by conventional methods like TIG or MIG welding. The welding process destroys the heat-treated microstructure in the heat-affected zone (HAZ), creating a region that is extremely weak and prone to cracking. If assembly requires joining, mechanical fastening (bolts, rivets) or adhesive bonding are the standard methods. Specialized techniques exist but are not common in general machining.
How does tool wear compare between 6061 and 7075?
Tool wear will be noticeably faster when machining 7075. Its higher strength and abrasive silicon particles increase wear on the cutting edge. You should expect to change or index inserts and end mills more frequently when running production jobs in 7075 compared to 6061. Using the correct, sharp tooling and optimal coolant application is critical to maximizing tool life.
What coolant should I use for 7075?
A water-soluble synthetic or semi-synthetic flood coolant is ideal. The primary function is cooling, not lubrication. The coolant must be applied generously and directly at the cutting interface to rapidly remove heat. For operations where flood coolant isn’t practical, a high-quality mist system is an acceptable alternative. Avoid using lubricant-heavy “tap magic” style fluids as the primary coolant for major material removal; they cannot remove heat effectively.
Is 7075 aluminum corrosion resistant?
On its own, 7075 has relatively poor corrosion resistance compared to alloys like 6061 or 5052, especially in stress-corrosion scenarios. This is why protective coatings are almost always applied. Anodizing (Type II or III) is the most common and effective method, providing a hard, corrosion-resistant oxide layer. For parts that cannot be anodized, other coatings like paint or powder coat are used after proper chemical pretreatment.