doubling voltage with two identical psu?

Is it possible to chain two 24v supplies together to make 48v but still be able to supply 24v? I need 48v for the stepper system and 24v for a laser control card.

Are there any disadvantages to using two power supplies other than space saving. I would like to save some cash and I already have a couple of large 24v 20 amp supplies.

As long as the two outputs are floating, that is, no connection to ground, then I would think that this should be OK. I wouldn't want to do this with high-voltage supplies as it's going to stress insulation but we aren't in that kind of territory at 24/48V.