Aluminum 2198 is one of the most recent alloys in the third-generation Al-Cu-Li aerospace family, developed specifically for fuselage skin applications on modern commercial airframes. Compared with 2196, 2198 carries less lithium and more copper, a shift that trades some of the maximum weight savings for better formability and a more forgiving fabrication window — important for an alloy that is typically rolled into large, thin sheet panels and formed into curved fuselage skins. Copper still does the heavy lifting for strength, forming age-hardening precipitates during solution treatment and artificial aging, while the reduced lithium content keeps density lower than legacy 2024 sheet without pushing the alloy toward the toughness and anisotropy issues seen in some higher-lithium, earlier-generation Al-Li materials.

Magnesium and a modest manganese addition round out the alloying scheme, supporting the precipitation response and helping manage grain structure through the rolling and heat-treatment cycle. 2198 is generally supplied in peak-aged sheet tempers and is prized for combining low density with good damage tolerance — fatigue crack growth resistance and fracture toughness that hold up well against the fatigue-critical service life expected of fuselage structure. On the machine, it behaves like a well-behaved 2xxx sheet aluminum, cutting easily but rewarding sharp, well-maintained tooling.

2198 cuts the way most 2xxx sheet and plate aluminum does: low cutting forces, clean shearing, and a strong preference for high spindle speeds over the slow, heat-limited approach used on steel. Because 2198 mostly arrives as sheet or plate stock destined for skins and formed panels, shop work tends to be dominated by face milling, edge trimming, drilling, and fixture machining rather than heavy turning.

The lower lithium content in 2198, compared with 2196 or 2199, means its machining behavior sits closer to a conventional 2xxx alloy than some of its higher-lithium relatives, but the same general cautions still apply. Lithium-bearing precipitates are somewhat more abrasive on cutting edges than plain copper-strengthened aluminum, and fine lithium-bearing dust from dry operations should be collected and handled rather than allowed to accumulate, since lithium is chemically reactive in fine particulate form.

Because fuselage skin stock is often thin and can be prone to flex or chatter if underclamped, workholding and fixture rigidity typically matter more on 2198 parts than tool selection alone. Sharp, positive-rake tooling with polished faces keeps built-up edge from forming, and standard aluminum chip-control practices apply throughout.