Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Andrew Mawson" <andrew@m...> 
wrote:
<snip>
> 
> The top HAS to be the reference as in fact it rests against a
> shoulder 
> on the collet to set the position in the spindle. Settting the Z
> height 
> for each tool isn't an option as I'm using a Heidenhain controller 
on 
> a 
> Bridgeport Interact 1 CNC mill, and although tool lengths can be 
set 
> individually when called this is not the case in the event of a 
> breakage. Variation in collar thickness isn't much - maybe 0.1mm 
max 
> but enough to spoil your day if you are isolation milling pcbs ! 
If 
> it were just drilling holes it could be ignored and allowed for in 
> the sacrificial underpad.
> 
> AWEM

My thought was that, as long as the collars were all the same 
thickness, there's a fixed distance from the bottom face of the 
collar to the top of it. That fixed distance could be taken into 
account in your collar setting device.

Regards, Bob