Western concert flute
Keywork

The keys can be made of the same or different metals as the tubing, nickel silver keys with silver tubing, for example. Flute key axles (or "steels") are typically made of drill rod or stainless steel. These mechanisms need periodic disassembly, cleaning, and relubrication, typically performed by a trained technician, for optimal performance. James Phelan, a flute maker and engineer, recommends single-weight motor oil (SAE 20 or 30) as a key lubricant demonstrating superior performance and reduced wear, in preference to commercial key oils).

The keywork is constructed by lost-wax castings and machining, with mounting posts and ribs silver-soldered to the tube. On the best flutes, the castings are forged to increase their strength.

Most keys have needle springs made of phosphor bronze, stainless steel, beryllium copper, or a gold alloy. The B thumb keys typically have flat springs. Phosphor bronze is by far the most common material for needle springs because it is relatively inexpensive, makes a good spring, and is resistant to corrosion. Unfortunately, it is prone to metal fatigue. Stainless steel also makes a good spring and is resistant to corrosion. Gold springs are found mostly in high-end flutes because of gold's cost.
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