Casement windows are usually made of wood or metal. The sash is attached to the frame with a hinge. A cranking mechanism called an operator attaches, via an arm, to a channel on the underside of the sash. Once the sash is closed, a latch grabs it and tightens it against the frame.
If a casement is difficult to operate, the solution is often as simple as cleaning and lubricating the gears in the operator or the other moving metal parts. If metal parts are broken, they must be replaced.
If the operator and lock work fine but the window is difficult to close, you may need to scrape and sand away caked paint. If bare wood is binding, then the sash should be planed to make it fit correctly.
Finding replacement parts can be difficult. If you can find the make and model of the unit, you may be able to contact the manufacturer or an online parts supply source to obtain the parts you need.
Expect to spend 1 or 2 hours on most repairs. You'll need minor mechanical skills for these projects, and before you begin, place a drop cloth on the floor near the window.
Remove the operator arm. To get at the arm, you may need to pry off a wooden stop. The operator arm shown disengages by means of a clip. Other types require you to slide the operator arm along the channel until it reaches the access slot. Then you push the arm down and pull it out.
Wire-brush away any rust and clean the arm with mineral spirits or other solvent. Apply lubricant to the joints.
Clean the gears with solvent and a toothbrush, then wipe with a rag. Slowly turn the crank to see that the gears mesh. If you see broken parts, replace the operator. Otherwise, apply grease, replace the cover, and test.
If the crank assembly still won't work, remove the mounting screws, slide it out, and buy an exact replacement.
The operator arm of some casements runs in a track that can clog with dirt and debris. Clean the track on the underside of the sash with a wire brush, then wipe with a solvent-soaked rag.
If a handle spins without opening the window, splines in the handle or on the operator shaft have been stripped. Buy a replacement crank that is adjustable to fit a variety of spindles. Slip on the correct ring, add the handle, and tighten the setscrew.
An awning window may have an operator at the side or at the bottom center of the window. Either way, the operator mechanism is similar to that of a casement window. If its operation is not smooth, remove the arm, which may be connected by means of a clip or two on the underside or side of the sash. Clean and lubricate the arm. Awning arms sometimes get bent. If you cannot straighten the arm using pliers, you may need to replace the operator.
To clean the operator arm on an awning window, begin by removing its cover (if necessary) and unfastening the mechanism from the sash.
Service the operator as you would a casement window: Remove the cover, clean, and lubricate. To remove an operator, straighten the arms and pull them through.
A casement window that binds even a little will be difficult to operate. Watch closely while slowly closing the window and mark any spots that bind. If you place a piece of paper covered with soft pencil marks (or carbon paper, if you can find it) between the sash and frame and then close the window, the binding spots will be revealed as dark smudges.