Grumble, grumble ... no more! The glass cutting system I've used for years has been put out to pasture, and it has been replaced with a new one. One that I built with plans bought from the website http://fusedglass.org/ This is a cool site for anyone working with glass. You can purchase the plans for $15 and download them to your computer. The instructions are simple to follow and they show pictures of all the parts you need, which are available at Lowe's and Home Depot. I'm not that mechanically inclined and had difficulty with some of the screws, but after a few "custom fittings" I finished the project!
You can see a video of the strip cutter being used at http://fusedglass.org/stripcutter
It works so well! I used my Morton grid under the cutter (like you see in the video) to catch all the little glass bits. Because of this, I had to find spacers the thickness of the grid on which to mount the hardware. Sitting on my work bench for years were two steel strips with holes that were the perfect thickness, so that's what I used.
Here's a photo of my strip cutter, which you will see looks just like the one in the video. Ha! I'm so happy with it and am confident that my glass cuts are straight. For some reason with the old system the glass curved at the end. For the glass boxes I make, the pieces need to be cut straight.
Here's a close shot of the part that slides. You can see the glass cutter (small gray piece) right next to the end cap.
If you have any questions, please feel free to contact me.