any advice for a 3 axis DRO for my mill?

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(02-22-2015, 06:24 PM)f350ca Wrote: I have a two axis on the mill. There is no backlash to compensate for on the knee, unless gravity fails. Couldn't be without x and y now but have never felt i needed one on the knee.

(02-22-2015, 06:51 PM)EdK Wrote:

(02-22-2015, 06:24 PM)f350ca Wrote: I have a two axis on the mill. There is no backlash to compensate for on the knee, unless gravity fails. Couldn't be without x and y now but have never felt i needed one on the knee.

Good point on the lack of backlash compensation needed on the knee.  

Ed

Ummm.... stupid question time. 

What difference does it make between the table and the knee if you have backlash in either lead screw?
If you have backlash in the X or Y and the table doesn't move - neither does the readout on the DRO, as the read head is attached to the table/saddle - not the lead screw. Backlash shows up on the dials - not the DRO. Isn't that one of the biggest benefits of using a DRO? 
What would make the knee any different?

Granted, I have my Z scale attached to my quill (which also has a slight amount of backlash in the rack/pinion) but changes in depth of cut are always spot on. If it jumps a couple of thou too far when moving the quill it shows up on the readout and I re-adjust accordingly.



My DRO also has the capability of combining two Z-scales. I could add another scale to the knee on my mill and the DRO will keep track of the tool position relative to both the quill and the knee. Pretty cool but way beyond my needs.