Cutting a thin slit

[whitmore]

I have a customer that requires a .020" slit about 1.5" long in a piece of 3/8 stainless. He said the slit could be, "...a little wider."

If it didn't have to be so thick, this would be an ideal place for electrochemical machining; in 5 mil shim, you'd just
laser-print a negative, apply bake-on resist, expose (with UV), develop, and etch (ferric chloride works, but
I've also used salt water and a bit of battery assist).

Practical methods for 0.375" plate include wire EDM, maybe laser cut. I'm thinking you'd want to send out either of those.
Here at home, I'd mill a step and clamp two plates together...

 

[MattM]

How many parts?

You may be able to source a slotting saw of sufficient diameter at that width but is will be slow going, the largest that MSC lists is 4" diameter with a 1" arbor hole, this will not go 1 1/2" deep with the arbor in the way.

Two parts, this is a prototype. He said if it goes top production maybe 100 at a time.

 

[RJSakowski]

For a prototype, a band saw would make the cut. The kerf for . 025" blade will be about .030". MSC sells band saw bldes in .015" and .020" thicknesses. For production, wire edm would be the way to go.

 

[4ssss]

What is a capped arbor?

You make the arbor with the back just smaller than the saw (smaller than the depth you need to go) and make the top a bit smaller also. In other words, if your using a 2" slitting saw, and you need to go .062 deep with the saw, make the backing and the top 1. 900 so the slitting saw will be supported. Hopefully all the diameters are concentric and you'll get a fairly accurate slot.