Machining 7075 Aluminum

Compiled 2026-04-04 · 5 chunks, 5 posts · aluminum · aerospace · high-strength · heat-treatable

Summary

7075 aluminum is a high-strength, heat-treatable aerospace alloy containing zinc as the primary alloying element, along with magnesium and copper. Significantly harder and stronger than [[aluminum-6061]], it machines more like a soft steel than typical aluminum. The T6 temper (solution heat-treated and artificially aged) is most common, offering ultimate tensile strength around 83,000 PSI compared to 6061-T6's 45,000 PSI. This increased strength comes with trade-offs: reduced machinability, higher cutting forces, and greater tool wear compared to softer aluminum alloys.

Speeds and Feeds

Turning Operations

Surface speeds: 800-1200 SFM for carbide inserts, 400-600 SFM for HSS tools Feed rates: 0.005-0.015 IPR for finishing, 0.015-0.030 IPR for roughing Depth of cut: 0.050-0.200" roughing, 0.010-0.050" finishing

Use positive rake inserts with sharp cutting edges. CCMT/DCMT geometry works well for general turning. Start conservatively at 800 SFM and work up based on tool life and surface finish requirements.

Milling Operations

Surface speeds: 600-1000 SFM (significantly lower than [[aluminum-6061]]'s 1200+ SFM) Feed rates: 0.003-0.008 IPT per tooth for finishing, 0.008-0.020 IPT for roughing Axial depth: 0.050-0.250" roughing, 0.010-0.050" finishing Radial depth: 10-40% of endmill diameter for slotting

Shop floor reality: Many machinists report starting around 800 SFM and 0.005 IPT, then pushing speeds up to 1000+ SFM once they establish good [[chip-control]]. Unlike 6061, you cannot "send it" at maximum parameters from the start.

Drilling

Surface speeds: 300-500 SFM for carbide drills, 150-250 SFM for HSS Feed rates: 0.003-0.008 IPR depending on drill diameter Use through-coolant [[carbide-drills]] when possible. 7075 work-hardens more readily than 6061, so maintain consistent feed to avoid dwelling.

Tapping

Surface speeds: 50-150 SFM Use cutting oil or high-quality coolant. 7075 taps reasonably well but generates more heat than 6061. Rigid tapping preferred over tap holders to maintain consistent feed rate and prevent work hardening.

Endmills

Roughing: 3-4 flute [[roughing-endmills]] with 30-45° helix, uncoated or TiAlN coated

  • Kennametal HARVI I TE series
  • Sandvik CoroMill Plura 1P221 series
  • Harvey Tool variable helix roughers

Finishing: 3-4 flute finishing endmills, sharp cutting edge, 30-35° helix

  • Avoid overly aggressive geometries that work well in 6061
  • TiAlN or uncoated carbide performs better than TiCN

Turning Inserts

Roughing: CNMG/WNMG with positive rake, sharp edge prep

  • Sandvik 1125 grade (uncoated)
  • Kennametal KC5010 (uncoated carbide)

Finishing: CCMT/DCMT with honed edge, 0.004-0.008" nose radius

  • Focus on sharp, positive geometry over tough edge prep

Drilling

[[Carbide-drills]] with through-coolant capability strongly preferred:

  • Guhring RT100U series
  • Sandvik CoroDrill 860 series
  • OSG Phoenix PXD series

Avoid standard twist drills above 0.25" diameter - the work hardening tendency of 7075 demands more rigid, shorter tools.

Common Problems

Work Hardening

7075 work-hardens more aggressively than [[aluminum-6061]]. Symptoms include rapid tool wear, poor surface finish, and dimensional issues. Solutions:

  • Maintain consistent feed rates - never let tools dwell
  • Use sharp tools with positive rake angles
  • Ensure adequate coolant flow
  • Take lighter cuts at higher feeds rather than heavy cuts at low feeds

Built-Up Edge (BUE)

The higher strength creates tendency for material to adhere to cutting edges, especially at lower speeds. Solutions:

  • Increase cutting speed above 800 SFM when possible
  • Use sharper tools with better surface finish
  • Apply cutting oil or high-concentration coolant
  • Consider climb milling over conventional milling

[[Chatter-Vibration]]

The increased cutting forces make chatter more likely than with softer aluminum alloys. Solutions:

  • Reduce axial depth of cut, increase radial engagement
  • Use shorter, more rigid tooling
  • Variable helix endmills help break up chatter frequencies
  • Consider [[high-feed-mills]] for roughing operations

Burr Formation

7075's strength creates larger, more tenacious burrs than 6061. Prevention:

  • Sharp tools with proper edge preparation
  • Climb milling where possible
  • Consistent feed rates to avoid work hardening
  • Plan tool paths to minimize exit burrs on critical surfaces

Shop Floor Tips

Heat Management Critical

Unlike 6061 which forgives heat buildup, 7075 becomes significantly harder to machine when hot. Flood coolant is nearly mandatory for production work. Many shops report better results with 8-10% coolant concentration versus the 5-6% used for mild steels.

Tool Life Expectations

Expect 30-50% of the tool life you get in [[aluminum-6061]]. Budget accordingly and don't try to push tools beyond reasonable wear limits - dull tools work-harden 7075 quickly, creating a spiral of problems.

Fixturing Considerations

The higher cutting forces require more robust workholding than typical aluminum work. Thin-walled parts deflect more under the increased clamping forces needed. Consider:

  • Hydraulic or pneumatic clamping for production runs
  • Multiple clamping points to distribute forces
  • Shorter tools and shorter overhangs where possible

Programming Strategy

Start with 70-80% of your normal [[aluminum-6061]] parameters, then optimize upward. The penalty for starting too aggressive is work hardening that ruins both the part and subsequent tool performance. Better to start conservative and speed up than crash and burn on expensive aerospace stock.

Surface Finish Achievement

Getting mirror finishes requires sharper tools and more attention to speeds/feeds than 6061. Many machinists report success with:

  • Light finishing passes at 1000+ SFM
  • 0.003-0.005 IPT feedrates
  • Sharp, uncoated carbide tools
  • Excellent coolant quality and flow
  • [[aluminum-6061]] — comparison with more common, softer aluminum alloy
  • [[chip-control]] — critical for managing the different chip formation in 7075
  • [[work-hardening]] — major concern with this alloy's machining behavior
  • [[carbide-drills]] — essential tooling for drilling operations
  • [[chatter-vibration]] — more problematic due to higher cutting forces
  • [[high-feed-mills]] — effective roughing strategy for this harder material
  • [[tool-wear-diagnosis]] — monitoring wear patterns in this more demanding material