Summarize:

When a Lazy Susan becomes stiff and difficult to rotate, the problem is usually caused by either the center shaft or the position of its bottom shelf. Lightly spin the Susan and note where it locks up, has difficulty turning, or has poor clearance.  If the center movable shelf begins to bind, it will prevent free rotation. In this situation, you’ll need to loosen this shelf. If the circular shelves slip down the center shaft, the bottom shelf can begin to drag, making it difficult to turn. You will need to adjust the height of this shelf to fix the problem. Look at the top of the center shaft. There should be one large bolt locking the exterior shaft to a metal sleeve positioned inside the shaft. This is the locking bolt for the shaft.  This bolt holds the center shaft in place and maintains the length of the shaft. Sometimes excess pressure from this bolt can cause the shaft to bind. On some models, the locking bolt might be located at the bottom of the Susan, however, in most cases, it will found near the top. If anything is inside your Lazy Susan, empty it so you have more space to work. Using a wrench or ratchet, loosen the bolt by turning it one-quarter of a full rotation counterclockwise. At first, the bolt may require some elbow grease to break loose.  Only loosen the bolt enough to manipulate the hardware inside the center shaft. On some models, this might require more or less than one-quarter rotation. Generally, it’s better to loosen the bolt in small increments. This will prevent you from loosening it too much, which could result in the alignment of the Susan being thrown off. Now that the bolt is loose, you’ll be able to adjust the center shaft. Slide the metal adjusting sleeve the bolt was holding in place no more than 1 inch (2.5 cm) to provide better clearance between the center shaft and top of the cabinet. Work in small increments when adjusting the center shaft. Large adjustments could cause the Lazy Susan to topple over. Use your wrench or ratchet to carefully refasten the locking bolt in place. Do not over-tighten the bolt. It should be looser than it was initially, but still tight enough to hold the adjusting rod in place. Most Lazy Susans should have two or more locking screws located at the center of each shelf. These screws hold the shelves to the center shaft.  When all of the shelves are held together by the front decorative panel, you will need to adjust the entire shelf system. In this case, there may not be screws located at the height of each shelf. If the shelves must be adjusted separately, you'll only need to work with the bottom shelf. Locate the locking screws in the bottom shelf only. Loosen the locking screws using a Phillips-head screwdriver or similar tool. Hold the screwdriver so its head meets the fastener straight on. Apply firm pressure down on the screw while turning counterclockwise to prevent stripping fastener hardware. Screws can be left in their holes once they have been unattached from the center shaft. However, you may want to set loosened screws off to the side to prevent any from getting lost. Carefully lift the bottom shelf or entire shelf system until there is roughly half an inch (1.25 cm) of space between the bottom shelf and the bottom of the cabinet.  The shelves may resist this adjustment and begin binding on the center shaft. Maneuver shelves until they are level and at a suitable height. Under no circumstances should you lubricate the center shaft. Doing so could prevent the screws from holding their position. Hold the shelf in place with one hand and use your free hand to tighten the locking screws back in place with a screwdriver. Take care not to let the shelf slip as you reattach fasteners, as this could cause it to become uneven or binding. Make the screws as tight as possible without stripping any of the hardware. The shelves must be stationary and secure to prevent this kind of misalignment.
Pinpoint where rotation problems are occurring. Locate the locking bolt to adjust the center shaft. Loosen the bolt. Move the adjusting rod. Tighten the bolt to finish adjusting the center shaft. Locate the locking screws to adjust the shelf position. Loosen the screws. Raise the shelves to finish adjusting shelf position. Tighten the screws.