A piggyback drill is typically connected to the coolant output. Thus, M7 and M9 commands can be used to switch to the piggyback drill as necessary.

Note that some configurations automatically turn on the drill when an M7 command is executed. Otherwise, an M3 is required to actually turn the drill on.

Commands

M7 is used to select (extend) the piggyback drill, M9 is used to deselect (retract) the piggyback drill. M3 is used to turn either spindle on. M5 is used to turn either spindle off. When the piggyback drill is retracted, M3 and M5 control on and off for the primary spindle, when the piggyback drill is extended M3 and M5 will turn the piggyback drill on and off.

M7 - Extend piggyback drill, disable primary spindle, enable piggyback drill.
M9 - Retract piggyback drill, enable primary spindle, disable piggyback drill.
M3 - Turn spindle on
M5 - Turn spindle off

Example

This example selects the drill tool (Tool #5 in this example), lowers the piggy back drill, turns on the drill, and drills three holes. Then it raises the drill and turns it off.

G90
M6T5
M7
M3
G0 X0Y0Z0.
G0 X5Y2
G1 Z-0.375 F100.
G0 Z0.
G0 X6 Y2
G1Z-0.375
G0 Z0.
G0 X7 Y2
G1Z-0.375
G0 Z0.
M9
M5
M30

Setup

Go to Setup > Tools. This is where all your tools are located, and a piggyback drill is simply another tool. You can use any tool number you wish. For this example, we'll use tool number 5. Go to the line labeled "5", and write "10" (ten, without quotes) in the Special Column. This tells the software that the tool does not have a tool stand.

Next, measure the X and Y offset between the main spindle and our piggyback drill.

- To do this, place a tool inside the primary spindle and drill a hole into a well secured piece of scrap material.

- Zero X, Y, Z

- Next, place the same tool in the Piggyback Drill and jog the machine until the tool fits exactly in the hole.

- Note the X & Y coordinates.

- Enter these values in the column labeled X Offset and Y Offset.

Now when you select the that tool number (M6T5), the software will automatically move the drill into position.

Tip: You can use the coolant output control to select/lower the piggyback drill. This will help measuring tool length easier. Follow the instructions located here: set tool offset. Note that some machines automatically turn on the drill when an M7 (or Coolant On) command is executed; for these machines, make sure you unplug the drill before touching off the tool!