Is 7075 aluminum easy to machine?

7075 is among the most pleasant aluminum alloys to machine. In the T6 or T651 temper it is about 150 HB, roughly half again as hard as 6061-T6, and that hardness helps: chips break shorter and clear more easily, the surface finish off a sharp carbide tool is brighter and more consistent, and the part deflects less under the cutter, so thin walls and fine features hold size better. Machinists rate it around 70-80% on the scale where 2011 free-machining aluminum is 100, in the same band as 6061 and above 5052 or 6063. Tool wear is still low compared with any steel, and cutting speeds of 300-1000 m/min (1000-3000 sfm) with polished, high-helix carbide end mills are routine.

The behaviour that separates 7075 from 6061 is residual stress. Heat-treated plate carries locked-in stress from the quench, and removing a lot of material from one side lets the plate bow. Always specify T651 (stress-relieved by stretching) or T7351 for plate that will be pocketed deeply, rough from both sides, leave stock, and let the part rest or stress-relieve before finishing; on thin, highly machined aerospace parts, roughing, a low-temperature stabilisation and then finishing is standard. The same stress makes thin webs and long fins move after the part is unclamped, so machining strategy and fixturing matter more than they do for 6061.

Otherwise the rules are the aluminum rules. Use sharp, uncoated or ZrN-coated carbide with 2-3 flutes and generous chip room, flood or mist coolant to stop chips welding to the tool, and high spindle speed with moderate chip loads. 7075 does not weld to the cutter the way soft tempers do, so the built-up-edge problems of 6061-O and T4 are mostly absent. It threads, drills and reams cleanly; roll-formed threads are common on aerospace parts. Cost, not machinability, is the reason to choose 6061 when strength is not needed: 7075 bar and plate cost roughly two to three times as much per pound, and the same part machines in about the same time.