Call your window's manufacturer to see if it it makes any replacement handles, or if there are other suitable handles for your make and model. Pick the new handle up yourself if the supplier is nearby, or have the handle shipped to your home.
Remove the old handle from its base to expose the gear underneath. This might be as simple as pulling it right off, though some models might require the use of a screwdriver.
Use a metal pick or other tool with a sharp end to clean out the main gear that is now exposed. You'll probably find that the ridges in the gear are filled with material after years of grinding and stripping.
Wipe the gear with a dry cloth to remove all the dirt and debris once the ridges have been cleaned.
Place the new window handle on top of the gear and fasten it into position.
Window handles, often referred to as window cranks, can be found on new windows in some homes but are most common in older ones, particularly those built in the 1950s. The window handle is a simple device that, when turned, opens the window. Give it a spin in the other direction and your window closes. After years of usage you’ll probably notice that the handle stops working. This is likely because the gears have stripped away at the handle. You can fix broken handles in a few easy steps.