They work very well. They are not cheap. I got them as scrap at work, and one has only one of the two transducers working, the other does not heat. The one transducer one has kerosene in it all the time and I use it for greasy grimey slimy goo. The other I have water in and put a small part in a glass container with the desired solvent or just soap and water and set it into the water. I also have a little plastic jewelry one I have not tried yet. I've used those on jewelry and they work nice, but I've not tried it on parts yet. The cheap jewelry model should work well with soapy water or use a small glass jar with solvent.

http://www.misonix.com/laboratory/La...or/HowTheyWork

I would like a bigger one, maybe a cheap stainless sink and a handful of these:

http://www.allelectronics.com/cgi-bi...ANSDUCER_.html

At a buck each, you could make a real big sonicator for much less than commercial.