What with playing around with my new tool setter and trying to decide where to put it I've come up with another set of questions which I've not really asked but now has been bugging me for a while. Home switches for a LinuxCNC controlled lathe. For the X axis I can see this as pretty simple as usually nothing impedes movement outward. Place it at the end of travel and it can serve as both a home and limit switch. The Z axis is more interesting. Before homing I imagine the tail stock has to be loosened and moved all the way to the right as far away from the headstock to ensure finding a home switch. Or a home switch could be somewhere in the middle but then which direction to search? Alright. So we've established a pair of X=0, Z=0 for home and this is set into the G53 X and Z locations. As I see it the next problem is with tools. Put a carbide insert cutter into the tool holder and it extends out to the centerline and to the left of the carriage. How does one determine, with that tool tip, where the lathe centerline is and set that so G54 X is 0.000? The chuck can be 3 jaw or 4 jaw, 5C colletor even a faceplate or the arbor for turning between centers. In other words 5 different Z locations relative to that G53 Z=0 position found when homing. And if the work is chucked in and sticks out 3" then do we try and make that end G54 Z=0? In the past for non-CNC, say I have a DRO on the lathe, I'll face off the end and then set Z to 0.000. If I want to turn 2" I'll move the carriage until the DRO reads -2.000. At this point I could reset Z to 0.000 or just make all cuts go from 0.000 to -2.000. Next if scratch the surface with the tool and set G54 Z=0.000 and then cut a pass at 0.010" I've now made the surface round with respect to the rotation. If I measure it at 1.020" in diameter then I now know the real X 0.000 centerline is 0.510". Set the G54 X value to 0.510" and from then on I can specify a final diameter and X positions for each cut which may already exist in the G Code. It's all about finding the reference positions on the lathe. Change tool and it needs to be done again. How is it generally done with LinuxCNC. Is there a tutorial for that somewhere? Thanks John
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