Or heat them with a torch, in addition to using penetrating oil.
If there is a knob on both sides, applying enormous torque to each knob should free them from the spindle, or twist the spindle in half.
Sometimes applying a tightening torque frees the spindle so you can then use a loosening torque.
This 'tightening first' works for windows that are stuck together with paint. You drive them closed further by using a hammer and a wood block.
Hacksawing through the knob shaft will reduce the area of rust that is available for gripping the spindle but will reduce the ft-lbs of torque you can apply to free these two materials.
JCWhitney and some H/W stores sell cutting disks, 1/32" and 1/16" thk that mount with an arbor into elec. drills. Figure one disk per knob shaft.
You can also just drill a series of 1/8" holes through the knob shaft which reduces the surface area of the rust.
Last edited by Wuzzat?; 01-23-2010 at 04:25 PM.