Alignment Pins

Alignment pins provide repeatable reference holes for double-sided PCB milling. TraceFab creates two or four symmetrical pin locations that can be drilled into the PCB and wasteboard before the board is flipped.

1. Prepare the setup

Secure the wasteboard and PCB so they cannot shift.
Establish the physical CNC XY origin and Z zero.
Choose straight, accurately sized alignment pins.
Test the pin-to-hole fit in scrap material when possible.

Alignment pins do not correct mechanical movement: loose or bent pins, a shifted wasteboard, the wrong board flip or a changed CNC origin will still misalign the two PCB sides.

2. Select the tool and pin size

Select Align Holes on the toolbar, or open Manufacturing > Alignment Pins.
Select a drill or cylindrical milling tool from the Tool Library.
Set the required pin size and verify the displayed spacing.

TraceFab Alignment Pins window showing four symmetrical numbered pin holes around a PCB — Four-pin mode mirrors the selected anchor position across both board centre axes.

Drill or cylindrical mill

Drill: creates a direct plunge hole at the drill diameter.
Cylindrical mill: uses a helical cut to create a larger pin hole.

Pin Depth is the total negative Z depth: it is measured from the active Z zero and is not additional depth below the PCB. If Z zero is on top of a 1.6 mm PCB, a 10 mm pin depth enters the wasteboard by approximately 8.4 mm. Verify the available depth before machining.

3. Position two or four pins

Two pins

Select 2 pins, then click the required anchor location in the PCB view. TraceFab places the second pin symmetrically across the horizontal centreline. This is the minimum repeatable setup.

Four pins

Select 4 pins, then click the anchor location. TraceFab mirrors it across both centre axes. Four pins offer more support, but inaccurate holes or pins can cause binding.

TraceFab Alignment Pins window while positioning two mirrored pin holes around the PCB — Choose the pin count, then click the anchor position in the PCB view.

Placement checklist

Place pins as far apart as the machine and stock safely allow.
Keep them clear of copper, the PCB edge path and clamps.
Confirm that every pin location remains inside the wasteboard and machine limits.
Use Reset before creating a different placement.

4. Calculate the alignment operation

Select Calculate after checking the tool, pin size, depth and placement. TraceFab stores one Alignment Pins operation for use in the Manufacturing window. Recalculate after changing the setup.

Calculate does not generate G-code. It prepares the alignment operation so it can be added to the manufacturing sequence.

5. Use the same pin as the XY origin

In the Manufacturing window, Set World origin can use one of the numbered alignment pins. Selecting a pin changes the XY coordinates written to the G-code; it does not set the physical work offset on the CNC controller.

TraceFab Manufacturing window with an alignment pin selected as the world origin — The selected TraceFab pin and the physical CNC XY zero must refer to the same pin.

Match the physical origin: set the CNC controller's X0 Y0 to the centre of the same numbered pin selected in TraceFab. Set Z zero separately using the intended work surface.

6. Follow a controlled board-flip workflow

Add the Alignment Pins operation before any step that loosens or flips the PCB.
Machine the pin holes and insert the alignment pins.
Machine the first PCB side.
Do not move the wasteboard, pins or CNC origin.
Flip the PCB in the intended direction, reseat it fully and secure it again.
Apply Mirror X to the required bottom-side sequence rows.
Perform a dry run above the PCB before cutting the second side.

Bottom-side operations are not mirrored automatically: verify the flip direction, Mirror X setting, selected pin origin and physical CNC zero before starting the second side.