The AGMA 21801 PDF can be obtained from the American Gear Manufacturers Association (AGMA) website or through various online standards libraries. You may need to purchase a copy or have a subscription to access the document.

AGMA 21801 is a standard for gear tooth surface fatigue life calculation, published by the American Gear Manufacturers Association (AGMA). Here's what I found:

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AGMA 21801 is a standard that provides a method for calculating the surface fatigue life of spur and helical gears. The standard is widely used in the gear industry to predict the lifespan of gears under various operating conditions.