Tool offset confusion

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25 Feb 2017 18:16 #88620 by kg2v
kg2v created the topic: Tool offset confusion
Hi,
I'm having an issue with tool offsets, and I'm a tad confused
I have read
linuxcnc.org/docs/2.5/html/gcode/tool_compensation.html
and
forum.linuxcnc.org/21-axis/2653-tool-length-offsets-in-emc

Now here is my issue - it doesn't seem to work - for me, and I don't know why

I took a block of aluminum, set it in my vise, and set the G54 coordinates by touching off (x,y and Z)

I then put my tool #1 (1/4 end mill) in a holder, went home on the Z, and issued
T1 m6, and sure enough, it asked for my tool one, and I put in in
Lowered the end mill till I could JUST slide a ,2 gage block under it, and I clicked "tool offset", and entered .2
Sure enough, the display now shows the tool at .2 and a tool length offset in the status bar of 4.12855

I then raised the Z axis to home, and issued a T76 M6 (there are only 15 tools in the table, I know about the 56 tool limit), and put my chamfer mill in, continue, and lower IT down till it just clears the .2 gage block, and click tool touchoff. Again enter the .2, and again see the .2 on the Z display, and a tool offset of 4.48149

I then raise to home, issue a T1 M6 again, and switch back to tool one (note, yes, they all have their own holders, their lengths are not changing). Lower it down till it just clears the gage block, and I', at .1841, and the tool offset reads the proper 4.12855 - aka I'm .016 off!!!!

Home again, issue T76 M6, put in the chamfer mill, check it - and it is at .6106, or .4106 off!! (way more than could possibly be backlash)

Now, if I run the mill up and down, with NO tool change, it all comes back to the .2 every time

I'm guessing I'm doing something wrong

BTW, that first link shows "tool table" in the dropdown, and I NEVER see that, I can only choose the various G54-G59.x options

Help! I have a job I really really need to run ASAP
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26 Feb 2017 00:27 #88623 by newbynobi
newbynobi replied the topic: Tool offset confusion
It seems, that you do not issue a G43 after the tool change. A correct tool change would be

T2 M6
G43

T76 M6
G43

NORBERT
The following user(s) said Thank You: kg2v
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15 Apr 2017 23:56 #91434 by kg2v
kg2v replied the topic: Tool offset confusion
Sorry for the very late reply, had forgotten my log in, but yep, that was the problem -
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