C90800 is a cast copper-tin bronze that pushes tin content a step higher than C90700, typically 11-13% against a copper balance of 85-89%. That extra tin increases the volume of hard, wear-resistant tin-rich phases in the cast microstructure, which trades a bit of ductility for improved wear resistance and load-carrying capacity under sliding contact — exactly the property profile that makes high-tin bronzes the traditional first choice for demanding bearing and bushing applications. Sand-cast tensile strength runs 35 ksi minimum, and centrifugally cast material — which cools and solidifies differently, refining the grain structure — reaches 50 ksi minimum with correspondingly higher hardness.

C90800's core reputation is built on speed reducers and worm gear sets, where its low coefficient of friction against steel worms lets it survive continuous sliding contact under heavy load with minimal wear. It occupies the same general niche as C90700 but with a composition tuned slightly further toward wear resistance, and it remains a standard specification anywhere tin bronze bushings or gear bronze castings are called out on a print.

C90800 machines similarly to C90700 but leans further toward the abrasive end of the tin bronze family, a direct consequence of its higher tin content. The greater volume of hard tin-rich delta phase in the microstructure — the same feature that gives this alloy its excellent bearing wear resistance in service — increases flank wear on the cutting edge more than a lower-tin bronze or a plain brass would. Cutting forces and heat generation both run somewhat higher than on C90700, even though the two alloys are otherwise very similar in strength and hardness.

Chip formation follows the same pattern as other cast tin bronzes: the coarser, less ductile as-cast grain structure fractures readily under the tool, producing short, well-broken chips that evacuate cleanly rather than tangling around the workpiece or tool. That's a practical advantage for parting and grooving operations in particular. The tradeoff is that this fracture-prone behavior comes from the same hard constituents that abrade the cutting edge, so tool life is governed more by wear resistance than by chip control.

As with other bronze castings, surface conditions matter — sand inclusions, porosity, and any hard oxide scale on as-cast surfaces should be cleaned up with a light first pass before committing to finishing parameters. PVD-coated grades with good abrasion resistance, moderate cutting speeds, and steady feeds get the most consistent results on this alloy.