2117 is one of the oldest members of the 2xxx aluminum-copper family and is best known as a classic rivet alloy. Copper is the dominant alloying addition, with small amounts of magnesium and manganese rounding out the recipe, giving the alloy a solution-heat-treated and naturally aged temper (T4) rather than the peak-strength artificial aging used on higher-strength 2xxx grades. That choice is deliberate: 2117 is intentionally kept in a softer, more ductile condition so it can be driven cold, upsetting the rivet shank to fill the hole and form a head without cracking.

Compared with structural 2xxx alloys like 2024 or 2214, 2117 gives up peak tensile strength in exchange for ductility and reliable cold workability, which is exactly what a fastener needs. It's produced almost exclusively as rivet wire and rod, and it shows up wherever aluminum structures are mechanically fastened rather than welded or bonded — aircraft skins, truck trailer bodies, and general sheet metal assembly. Because it's supplied and used in a relatively soft temper, 2117 machines noticeably easier than age-hardened 2xxx alloys, though its main "machining" operation in practice is the shearing and upsetting action of the riveting process itself rather than conventional turning or milling.

2117 in its T4 temper is a soft, ductile aluminum alloy, so from a pure metal-removal standpoint it behaves like most non-heat-treated or lightly aged aluminum: low cutting forces, high thermal conductivity that pulls heat out of the cutting zone, and a strong tendency toward built-up edge if the tool isn't sharp or is run too slowly. Because the alloy is deliberately left soft for cold riveting, it's actually more prone to gumming and edge buildup than a fully aged 2xxx alloy like 2024-T3, since there's less work-hardening resistance in the chip to help it shear cleanly away from the tool.

Sharp, positive-rake geometry and polished cutting surfaces are the standard fix — a keen edge shears the soft material instead of pushing and tearing it, which is what causes the smeared, built-up-edge finish that soft aluminum is notorious for. Running at higher surface speeds, rather than easing off, usually improves the finish rather than hurting it, since aluminum doesn't generate the same heat-driven tool wear that steel does at high Vc.

Chip control is the other practical concern. Soft, ductile aluminum tends to produce long, stringy, continuous chips rather than the segmented chips typical of harder alloys, so chipbreaker geometry and reliable chip evacuation (air blast or coolant) matter more than raw cutting parameters. In practice, most 2117 in the field is processed as rivet stock rather than machined from bar or plate, but where it is turned or drilled — trimming rivet shanks, prepping fastener blanks — these same soft-aluminum principles apply.