Two methods come to mind:
1)Electrochemical machining (ECM) using a wire cathode and a 300 g/L NaCl electrolyte. see ASM Handbook, vol. 5, Surface Engineering or vol. 16 Machining.

2) Get some self-adhesive vinyl sheet (with peel-off protective backing). Punch the holes in the vinyl (maybe over some rigid cardboard), then attach to the steel and do some acid etching. It would speed things up if you can make your sheet the anode. HCl or warm sulfuric should work.

Hope this helps, & please give feedback.
Ken

We commonly get prototype parts made from thin stock by a Photo-Resist etching house. I think they use the same basic process as circut board etching. From my tour I think they use a Ferro-cholride etchant and a certain temp. I know that the edge is usually pretty good although may have a peak in the center (the last to etch away). I'm not sure bout .030 low carbon but they handle 420 hardened stainless no problem. You might want to send this type of job out to a place like that since the chemicals used are probably hard to dispose of.

(Im not sure if I can post the below)
Their name is Micro-photo they're in the Detroit area



Nick

The company Photofabrication has a good design guide on this type of process.  You can obtain more information using the following link:

http://www.photofabrication.com/designguide.html

Another possibility is laser processing.  I saw a similar application during a tour of 3 Dimensional Services in Rochester Hills, MI.  A steel dome that was probably more like 1.5 mm thick was having ~ 1000 holes pierced in it by a CNC laser set-up.  You can obtain more information on 3D using the following link:

http://www.3dimensional.com/