Method and apparatus for selectively removing metal from a metal part

Claim 1

A METHOD OF SUBSTANTIALLY EQUALLY AND CORRESPONDINGLY ETCHING METAL PARTS WITH AN ETCHING SOLUTION, WHICH COMPRISES SECURING A PAIR OF SAID PARTS TOGETHER IN BACK TO BACK RELATION SO AS TO MASK THE ADJACENT BACK SURFACES OF SAID PARTS, SAID PARTS HAVING RESPECTIVE OPPOSITE SURFACE PORTIONS EXPOSED FOR ATTACK BY SAID ETCHING SOLUTION, SIMULTANEOUSLY IMMERSING SAID PARTS IN AN ETCHING SOLUTION WITH THE PLANE OF SAID BACKS SUBSTANTIALLY NORMAL TO THE SURFACE OF SAID SOLUTION, SAID PARTS BEING INTRODUCED INTO AND WITHDRAWN FROM THE SOLUTION AT A RATE SELECTED TO VARYING THE PERIOD OF IMMERSION AND AMOUNT OF ATTACK OF THE ETCHING SOLUTION ON DIFFERENT SECTIONS OF THE EXPOSED SURFACE PORTIONS OF EACH OF SAID PARTS, CORRESPONDING OPPOSITE SECTIONS OF THE EXPOSED SURFACE PORTIONS OF SAID PARTS, WITH REFERENCE TO THE SURFACE OF THE SOLUTION, BEING THEREBY ETCHED SUBSTANTIALLY THE SAME AMOUNT.

Claim 2

A METHOD OF SUBSTANTIALLY EQUALLY AND CORRESPONDINGLY ETCHING METAL PARTS WITH AN ETCHING SOLUTION, WHICH COMPRISES SECURING A PAIR OF SAID PARTS TOGETHER IN BACK TO BACK RELATION SO AS TO MASK THE ADJACENT BACK SURFACES OF SAID PARTS, SAID PARTS HAVING RESPECTIVE OPPOSITE SURFACE PORTIONS EXPOSED FOR ATTACK BY SAID ETCHING SOLUTION, SIMULTANEOUSLY IMMERSING SAID PARTS IN AN ETCHING SOLUTION WITH THE PLANE OF SAID BACKS SUBSTANTIALLY NORMAL TO THE SURFACE OF SAID SOLUTION, SAID PARTS BEING INTRODUCED INTO AND WITHDRAWN FROM THE SOLUTION AT A RATE SELECTED TO VARYING THE PERIOD OF IMMERSION AND AMOUNT OF ATTACK OF THE ETCHING SOLUTION ON DIFFERENT SECTIONS OF THE EXPOSED SURFACE PORTIONS OF EACH OF SAID PARTS, CORRESPONDING OPPOSITE SECTIONS OF THE EXPOSED SURFACE PORTIONS OF SAID PARTS, WITH REFERENCE TO THE SURFACE OF THE SOLUTION, BEING THEREBY ETCHED SUBSTANTIALLY THE SAME AMOUNT.