TL;DR - Some things to keep in mind...
- MAKE SURE YOUR GROUNDING CLIP/MAGNET IS ATTACHED TO YOUR MILL! If you don't, you could damage your mill, your touchplate, or at worst, your CNC machine.
- Double check your touch plate dimensions with a good vernier caliper. You may find it's not quite the same size as the documented dimensions.
- Go slow with the feed rate. You don't want to slam the mill down into the touchplate. Sneaking up on it slowly will allow for a more accurate measurement.
- Keep the tool distance reasonable. This is the distance between the tip of the endmill and the top of the touchplate. If you begin zeroing and the this space is greater than the value you've entered here, you'll get into an error/alarm state and have to home and start over. I generally like to set this to 1 inch (25.4 mm) and then position the mill .5" (12.7 mm) off the surface of the touchplate.
Why?
Well, there are a ton of touch plates out there, not to mention it's possible to make your own. The real trick is the zeroing routine. I hope I've made that easy for you dear reader.
Who is this for?
Anyone who uses a grbl based board and a touchplate. My personal setup is a Triquetra connected to a Shapeoko XXL and CNCJS running as my gcode sender.
Touchplates sound scary, I'll stick with my paper scraps.
They're really not. I ended up pulling the trigger when it was super important to have zero set accurately for a project I was working on. There just isn't a way with paper scraps to do that. With a touch plate, you can change bits and set zero perfectly and accurately.
This is all in addition to having good eye/ear/lung protection while you work around a CNC machine. If your feeds are too fast, even while probing, you may find the flying shrapnel of a carbide endmil headed in your direction.