Need info on where to cut oncidium spent flower spike?
 

I know it's a little late, but I have two oncidiums (don't know which ones they are) but both have finished flowering. I cut the spikes close to the leaf joint, and all seems fine-but I realize now I have no idea if that was right. They are showing no sign of spiking since, and it's been about 6mths. These were given to me by two seperate friends who didn't care to keep them. I have never seen the actual flowers....

Most oncidiums do not rebloom from old spikes. You have to wait for new ones. With the exception of tolumnias and psychopsis (maybe a few others), those rebloom on old spikes.

As already noted, Oncidiums do not normally re-bloom from old spikes. You will need to wait until new growths are mature enough and the plant is happy enough to send up a new spike. Old spikes can just be cut back far enough to not be unsightly, or as far as you can manage without damaging sheaths or pseudobulbs, your preference.