Sandpaper Sheet Cutting Guide

Back when sandpaper had plain old paper backing, setting up a guide with an edge to tear against was easy. Nowadays, with the advent of film backing and other advanced materials, tearing isn’t easy — or sometimes not possible at all.

I wanted to make a guide that would allow me to easily cut standard sizes from a sheet of sandpaper. My first pass at it used brads to register a MDF strip to guide the blade. It worked OK, but the play in the registration of the strip caused some error in the cuts. It was particularly evident in the 1/4 sheet 2-3/4” strips that the Preppin’ Weapon sanding block uses. By the time I got to the final cut, the last sheet was often off by up to 1/16” and didn’t cover the full width of the sanding block. I had slightly better results by cutting the sheet in half at 5-1/2” and then cutting those two, but it still wasn’t perfect.

The last straw was when I bought a 1/3 sheet sander, and the old guide didn’t have brads for that size. Spending time adding them to a flawed design didn’t make sense, so I came up with a new plan.

Here’s a shot of the old (retired) guide:

The updated design:

I decided that nothing could be truer and more accurate than sheets of MDF right from my table saw. I made up a simple base plate with a side and top strip of 1/4” MDF and cut guide plates from MDF as well. The plates are all perfectly sized for the cut. I had to sneak up on the exact width for the 1/3 sheet plate, but with it, I can cut three strips from a sheet that are exactly the same size. The green surface is a piece of cheap kitchen cutting board plastic that I picked up for a couple of bucks at the outlet mall. It keeps the blade from digging into the MDF as I cut. The old guide had gotten some pretty deep channels over time. (As an added bonus, a narrow strip I cut from the leftover material is perfect for elevating a plane iron on the sharpening stone for grinding a back-bevel).

It’s a bit less convenient to have so many pieces make up the overall guide, but the results have shown it to be worth it.

— Rich

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner