Please help at wits end with strange offset tool paths

Perhaps this is the wrong place to post this but I am doing so incase someone thinks it may be within probe basic as the issue.

Problem: When I probe a corner of my 6-sided precision ground stock, and then run the tool path, the cuts are offset. At the probed Y side, the endmill is a few mm AWAY from the side not cutting and on the opposite side it is digging in a few mm causing a crash. It appears something similar is happening on the X side as well.

Machine: Taig CNC with linuxcnc 2.9.4 using probe-basic

Here is what I have done to debug:
1. Indicated my vise jaws, confirmed vise is in line with X and Y
2. Indicated my probe tip, made sure it is straight
3. redid probe basic probe tip calibration which results in a number in line with my other machines (I use the same aliexpress 3 axis probe)
4. confirmed the table is trammed, column is perpendicular to the table
5. Tested axis travel with a dial indicator mounted in-line with each axis. When I command movement of 12.7mm the indicator reads 0.5 inches so it appears the axis are travelling the correct amount (both X and Y)
6. Using fusion360, verified my endmill dimensions are correct (9.525mm), toolpath seems as usual, simulation looks correct

Additional information:
1. I added a screenshot of my 3/8 endmill on the side I probed, it is hard to tell but the endmill is about 2mm away from actually touching the side whereas it should be digging in 0.2mm into the side and cutting
2. added the start of my gcode file

Question: Do you all have any other suggestions on what I can try to do to debug the issue further? This is the only machine I have issues with. I have a linuxcnc lathe and tormach mill with pathpilot and both work correctly.

You have a probe diameter set in the tool table?

Does your probe calibration correctly measure the calibration ring/pin used?

Are you correctly setting up your cam post processor?

Have you verified using mdi commanded moves to rule out based cam settings?

Is your axis calibration correct?

Hey so I did another test - setting the origin manually with an edge finder makes it work as expected.


However, I can't for the life of me think of what the actual issue is in that case then? The probe calibration all looks correct, the diameter is set in the tool table.

When I compared the edge finder origin vs the probed origin, the probed origin is about 0.815mm off in each of the axis. The probe diameter is 1.95mm, calibration seems correct.

Do you think it is more likely a probe issue or a linuxcnc issue? Clearly the post processor/CAM is correct

I just can't think of anything mechanical with the probe being the actual issue

edit: My probe tip diameter is 2mm, when I do probe cal it says the probe cal offset is 0.97mm - and measures the circle as 5mm

EDIT2(MORE IMPORTANT): also if I use the probe to probe the edge, then move to the origin and slide the probe across either X or Y wall of the metal at the 0 value for that axis, it does retrigger the probe, doesn't that mean the probe is functioning correctly and its a linuxcnc side issue?

I probably worded the statement poorly - but the table, vise material column is 100% trammed with each other no question


I would just disregard that statement, what I meant was when I probe the corner the probe does appear to be in the correct location, at least close enough that if I brush the probe along that wall, the ball (whose central axis is now along X or Y) deflects enough to re-trigger, meaning the probe is fairly close to the true corner.

However, the easier statement is that when I compared the origins, the probed origin is around 0.815mm off the true corner (as compared to using a mechanical edge finder). So for some reason, when I use my probe, the origin that is recorded is 0.815mm AWAY or INTO the actual wall.

I use a dial test indicator to make sure the probe ball tip is concentric so its definitely not that.


Can there be some issue in probe-basic or linuxcnc that is not correctly applying the diameter? Or miscalibrated somehow internally but on the UI shows the correct value??

0.97mm calibration offset is HUGE, you have wrong going on there, that should just be the trigger distance of the probe. You should use a larger calibration object so you aren't in an acceleration state. The cal offset should be a really small number, 0.04-0.08mm for most decent mechanical hobby probes. The probe tip diameter must be entered into the tool table in the column. (I this is where you're issue is coming from and why your cal offset is so large. Use only fast probe feed rate (set slow probe feed to 0.000). Use something like 200mm/m fast probe feed rate.. Be sure to reset the offset prior to running calibration. Run in probe position only mode for calibration. Make sure your step of width is a decent amount past the edge, at least 10mm or so.