Originally Posted by
rwskinner
The reason for two plates is so you only have to zero the first bit to the work piece with the movable plate. Once that is done, the bit is touched off on the fixed plate and the difference is stored. It has nothing to do with the spoil board height at all.
The next time a tool change is called for in the G-Code, the bit is changed and you press Cycle Start then the bit is touched off the fixed plate and now the new bit length is known.
The entire concept of the dual plates is so you do not have to touch each bit off on the work piece which is very handy especially if your original surface has been machined away.
The fixed plate can change heights if needed during spoil board surfacing or whatever, it just can't change after you start a job and reference the first bit.
I hope I explained it well.
Richard