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I keep meaning to ask about gear changes. My lathe has a 6 speed gearbox, can LinuxCNC recommend correct gearing, or should I choose a gear, then run the program and evaluate how hard it is running the VFD to check if I need to change gears?

Soundreflections wrote:
Both are possible.

What might be quick-and-easy would be to make a table of part diameter and material with the optimum gear. You want to use the highest gear which will still have a reasonable VFD frequency at max diameter so that you aren't running out of speed on the smallest diameter.

Any idea where I can get a table of recommended cutting speeds for different metals? I have found many requests for such a table, many people saying they will try and make one, but not yet any actual table. It is possible I am searching the wrong key words, but that would be helpful, in manual and CNC. Presumably I can then tell LinuxCNC what metal I am using, it can ask for the right gear combination. Lazy I know, but even a manual table would be fine. I often try to cut quite slow, finish as fast as possible. Not sure what to look for to find the correct speed. I have often thought video clips of CNC cutters are running very fast when they cut, so I thing I am on the wrong track.

I have now ordered a MODBUS interface for my drive, hoping I will have a reversible parallel port, but it won’t cost too much so I am happy with it, just need to figure out how to program HAL. I am first making my stepper drivers and then I will get the PC down and see if LinuxCNC is happy with it. Wish I had more free time for this!

Look for SFM calculators or charts...

I have found an ideal box among some stuff my work is throwing out. It has latches closing it and the hinges are slide off type. It also has a full metal insert on which all electronics can mount, it can then simply screw in to the box.


I have also started working on my PC. Finally got the thing to boot (long time been standing, looks like it now had a bad RAM and video card.). Looking through the BIOS settings I can set my parallel port to Bi-directional, so hoping I can believe that.

I am wondering how to configure LinuxCNC for serial MODBUS spindle speed. I am hoping it will all be clear and easy once I actually set it up. At this stage I get a black screen once Linux starts, need to play with VGA=778, to try and sort it out, just not had time yet.

Thanks for the SFM hint, I have now found some SMM? charts.

Soundreflections wrote:
Ah metric would be Surface Meters? per Minute I guess. Also for the most part the charts depend on good tooling and rigid machine and are usually a good place to start.

John