making very fine slots...

Let suppose, for the sake of arguement I have a 60mm dia brass disc, approx 1mm thick. Around the periphery, approximately 3mm in from the edge, I wish to cut 400 slots, each 2mm radially and 0.23mm wide.

To index the disc it will be mounted on a backing sheet of some description and attached to a stepper which will be 1/2 stepped to give 400 indexable locations.

So what to cut with? PCB routing cutters can get close to that level but would need careful depth control to get a consistent width. I've seen MicroCarbide endmills at 0.2mm on the web, but how realistic is that?

Laser, spark erosion, what?

You want one of these

http://cgi.ebay.co.uk/RDGTOOLS-3-HSS...mZ260440292094

or better still one with a smaller OD so it doesn't wobble. these will cut your slot in one pass.

Good try John, but the slots have to be a controlled length, not right to the edge.

Oops missed that bit.
What about doing this on a 54mm disk and pressing a 3mm ring on afterwards ?

laser - I doubt they will cut copper alloys
edm - yes but at a cost
0.2mm milling cutter in a top-notch cnc - no problem
0.2mm milling cutter in a converted drill/mill 1 or two notches then snap...

How about photo-etching?

Laser will cut brass but the edge finish is $hit and at 0.23mm wide probably impossible.
Spark eroder will do this no problem but you need a graphite or copper master and cutting this gives the same problems as cutting the slots.

What is it for ? can the design be altered to suit a better method?