Horizontal Drilling using G81

[rene-dev]

drilling cycles only work in the negative direction. while on most machines this makes sense, I also hit this limitation which was already reported on the forum. https://forum.linuxcnc.org/20-g-code/29162-horizontal-drilling-using-g81
I removed the checks, and it works fine in the other direction. no surprise, math also works with the other sign. Any objections to remove the check?

[grandixximo]

I don't think there are valid objections, the limitation itself stems from a lack of imagination of where a drill bit could be mounted, and at most you'd be "drilling" away from your part, which is safe and fairly easy to fix.

[rene-dev]

https://github.com/rene-dev/linuxcnc/tree/horizontaldrill

[grandixximo]

On second thought, reading the patch, your warning is accurate. A swapped R/Z no longer errors, it rapids to R and cuts the other way, so my "safe and fairly easy to fix" claim was wrong.

How about keeping the check as an INI option instead of removing it: [RS274NGC] ALLOW_REVERSE_CANNED_CYCLES, default 0 so existing machines keep the typo protection, 1 for machines that drill horizontally. Horizontal drilling works, nobody loses the guardrail silently on upgrade.