Frage Is Tool Length Offset really important for us?

Forewords: I'm a newbie using LinuxCNC

After spending a lot of time to learn what the magic word TLO means (and how G43 code works) a doubt arises in my mind: on a Stepcraft machine, do I really need to set the TLO for every tool?
I mean, it's impossible to fix the milling bit exactly in the same precise Z-position every time, so the offset-value eventually stored in the Tool Table is not exact in any case. I'm wrong?

From what above, I think that with the steppie one has just to set manually the zero-working coordinates above the piece (the so called WCS - Working Coordinate System), turn off any TLO compensation (command G49), and then start milling. I'm wrong?

T did not spend any time to understand G43 (Don't even know it) but understood that tool lenghth is important.

But I address it simply: I use Mach3 and have a sensor+macro to measure Z-Zero. I just do this after every tool change and so far it worked.

The reason might be that we do not have automatic tool change, and I have no rings on my tools to set them automatically to right hight. If you have the first you may benefit from a more sophisticated tool change macro understanding tools in the changer. If you have second you don't need it at all, just to pause somewhere being able to change the tool.

For those havein none from above we measure somehow new tools a) difference to old tool or b) new Z-0

Danke Frank.

Just a question: what happens if (maybe one time in your life) you have to change one tool during the milling process?
It's possible to:

- pause the milling proces
- take the tool in a "parking" position
- change manually the milling bit
- return to the old position
- continue the milling process

It depends on the CAM software that you use or what?
Or maybe is better to create two distinct g-code process? Let's say, one with tool A and one with tool B? What you do usually?

I have a stupid tip for LinuxCNC+G-simple users.

Problem: G-simple always produce a G43 command for Tool Length Offset (TLO).

G-simple forces you to select as minimum one tool from his own "Tool table". That selection produces a "G43" command in the output gcode file, so TLO for that tool will be calculated even if you don't want it at all. I haven't found any option to disable this behaviour when exporting the gcode.

Solution 1:
Manually erase the line from the gcode file (but it will be overridden by G-simple next time).

Solution 2:
Open the Tool Table editor in LinuxCNC and set Z=0 for that tool number, then restart LinuxCNC (or reload the table). The new TLO will be zero, so it will have no effect during the milling process.