I want to etch a 2 inch wide Ford emblem on brass with the name “Ford” contoured with a diamond drag bit with the inside of the letters left as clean brass. Outside the letters I want the brass painted blue. I approached this as if it were a wood sign by masking first with Oracal but I was unable to cut the mask clean around the letters ( I think it is just too small). I tried a cheap 30 degree v bit at 10K RPM, 0.002 in deep. The idea was to cut and peel the mask off around the letters, paint blue, unmask the remainder and then diamond drag the letters. Has anyone done anything like this successfully or maybe there is a completely different process I should be following?
I would make a guess that this is what causes the Oracal tearout: the catch about vbits is that their tip has a speed of zero, so when carving at such a shallow 0.002" depth you are basically dragging that tip across the surface, it’s not going to make a clean cut even with an expensive vbit. Especially since I understand you would like to cut through the Oracal but not scratch the surface of the brass (which will be left for the DDB to do). Sounds like Mission: Impossible. I wonder if using a laser with carefully selected parameters to just cut through the Oracal would work.
You could cut template letters out of any thin material, attach them onto your piece of brass somehow, paint over them, then remove them ?. And then run the contour toolpath with the DDB to (hopefully) highlight the contours. I wonder if a shallow v-carved contour, say 0.02" deep, would not be better at highlighting the contours. DDB engraving on metals tends to be very faint when only using contours, I would not be surprised it it weren’t visible at all, at the edge of that blue paint.
Thank you for the reply. I think I am going to accept Mission Impossible. Good reminder on V bit behavior and their limitations.