[sdiy] Re: Possibly quick / cheap pcb service - anyone interested?

[Ingo Debus]

Am 31.01.2010 um 21:53 schrieb Olav Martin Kvern:

> You mentioned clamping--one thing that made a huge difference for  
> me was getting a vacuum hold-down unit. It keeps the boards  
> absolutely flat. With clamps, I found that the center of the board  
> would always bow upwards, and that the height of the board could  
> vary from side to side due to uneven clamping pressure.

Isn't there some pin that slides on the PCB along with the milling  
tool that keeps the distance between board and milling tool constant?  
I used to work with a LPKF PCB milling machine many years ago.  
Without that "pilot pin" (or whatever it's called) it would never  
have worked. While doing a larger board the distance still had to be  
readjusted from time to time, probably because the tool wore down.
Bowing up of the board was never a big problem, because the pin  
pressed the board against the bed where the milling was done.

Ingo