Laser Cutter Cross-hair Guide for under $10

What is it?
Fully adjustable laser cross-hair aiming guide for the FSE 40W laser that can be made using your laser cutter and assembled in less than an hour.

Items you'll need:
2 Red Line Laser Modules Item# 5928 from http://www.dealextreme.com/ $3.96 each
1/8" Acrylic, 3"x3"  (scrap from another project?)
Mounting hardware (I used a pair of screws and nuts on the FSE 40W laser that aren't needed)
Electrical tape
Silicone adhesive (or other glue)
100 Grit sandpaper
Soldering iron/solder

Download and vector cut the SVG file HERE. (Go to File -> Download Original) I used 20% Speed, 100% Power (@ 15ma). You should create a bracket that looks like this:

Unplug the original red laser and unscrew its mounting bracket.  Install the Acrylic bracket as shown below and attached the original red laser mounting bracket to the channel on the right.  I used the machine screws and nuts holding the sheet metal that hides the Retina Engrave Card to mount the Acrylic bracket (any small nut and bolt should work fine).

Remove the "line forming" lens from one of the two line lasers (just unscrew the cap) and glue it to the original FSE red dot laser with the smooth side out, being careful to not obscure the path of the laser with glue.  Solder the terminals of the second line laser to those of the FSE red dot laser (red to red, black to black).  Your lasers should look like this.

To achieve a narrower line, mask each lens with electrical tape leaving a small slit in the center.  This will create a more precise cross-hair.  Position the slit perpendicular to the direction of the grooves on the lens.  Cut off the extra tape.

The hole on the bracket is undersized so that with a small amount of sanding you can press fit the line laser into the hole.  Use your 100 grit sandpaper to open the hole just enough to press in the line laser.  This should be a tight fit.  Mount the original FSE red laser (now with attached line lens) in it's original bracket.

By adjusting the four screws, you'll be able to align the X and Y axis lasers to cross where the cutting beam meets the material, regardless of the height of the material.  This performs the same job (or better) than the $300 beam combiner offered from FSE.

This project was inspired by Rich Olson's work at Nothing Labs: http://nothinglabs.blogspot.com/2011/06/20-laser-cutter-crosshair-aiming-system.html