CNC 3020T T-Slot Touch-Off Plate

These are the parts needed for using a $19 touch probe from Amazon as a $100 touch off plate on a CNC 3020T Router. Using these parts I've been able to machine aluminum with 4 tool changes at a near perfect accuracy (less than a thou surface deviation between tools) Not bad for one of the "cheap" chinese CNC machines!

This tool consists of two printed parts and a few other bought or found parts. Of course you need one of those touch probes from Amazon, and it should have the flat v-grove style mount (you might have to edit the base clamp to make it attach to your probe if you get a different style,) and then you'll need to print two parts. The first part clamps to the top of the probe and provides a flexible shelf to register a larger area of pressure against the probe tip.

The second is the base that slides into the 3020T's slots (check the slot profile in the picture to make sure yours match of course.)

A CR2032 battery makes the perfect touch plate, I glued mine on with a little super glue. Mount and fix this to the side of your work area, I clamped mine to ensure it didn't move which would completely wreck the calibration after the job start.

Using your first endmill, area clear a consistent level on your work piece (even if it's just a few thou), when that job is finished, jog your tool over to the center of the battery (touch plate) and lower it until it engages a bit. Set the probe to 0 by rotating the dial and then use your router controls to jog up and down until you're reading 0. Note the coordinates on your CNC machine (you should only have moved the machine via jogs at this point.)

Now that it reads 0 on the dial indicator, lift the z axis manually and swap your tool, then lower it manually until the new tool reads 0. Near perfect tool change!

You should use some screws to clamp down the base in the front and the back btw, again, if this moves after the initial calibration (after you area clear and note your coordinates when you find 0) your tool changes will not be accurate.

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