Parallelogram mechanisms
Many table designs utilize a parallelogram mechanism to raise the table to a proper working height:
With these mechanisms you may notice an audible "thunk" when the table is fully lowered, or you may observe the table base lift slightly, maybe up to 1/2 inch, when the table reaches its fully lowered position.
More times than not, the cause is a majority of the pivot bushings in the mechanism are worn out. It is easy enough to replace the bushings and pins, all are done at the same time, we just don't want the wear to go so far that it damages the frame.
The bushing on the left is still intact. The bushing on the right has broken from its flange.
photos above: This is what happened to the frame from the broken bushing.
Photo Below: replacement parts
Fun fact: this is “supposed” to happen. We want the bushings to wear out so that the table frame incurs minimal damage. This is where we come in and make the repair and ensure your table is running at it’s optimum.