Woodworking Tips
Woodworking Tips Index
Cutting Plywood Down to Size – Rough Cuts
Cutting a full sheet of plywood (or MDF) down to size on a table saw can be a challenge. The sheets are heavy and awkward to move around. And even after you wrestle it into position, the surface veneer has a frustrating tendency to chip out as you make the cut. Fortunately, there are several things you can do to simplify the job — starting with the initial rough cuts.

Rough Cuts – The first step is to lay out the pieces on the plywood. As a rule, I allow ¼" “extra” all the way around. This provides enough material to make a final clean-up pass later. But just because the pieces are cut to rough size doesn’t mean you want a rough cut. The goal is to end up with clean, straight edges that can ride against the rip fence on the table saw (or be placed against the miter gauge).

 
Cutting Guide – To accomplish this, I use a circular saw and a cutting guide that clamps to the plywood, as you can see in Figure 1. The guide consists of two parts: a hardboard base that serves as a platform for the saw and a wood fence that guides the saw.

The nice thing about this cutting guide is it has a reference edge that aligns the saw blade with the layout line. By aligning this edge with the layout line, the blade makes a perfectly straight cut exactly where you want it.

To make the cutting guide, start by gluing the fence to an extra-wide base. The reference edge is formed by running the base of the saw against the fence and trimming off the waste.
 

Foam Support – You’ll also need a way to support the plywood during the cut. The best way I’ve found to do this is to lay the plywood on a sheet of foam insulation, like the one shown in Figure 2. (It’s available at most home centers.) Besides providing support, the foam lets you crawl onto the sheet of plywood. Which is handy when you need just a bit more “reach” to complete a cut.
"Good" Side Down – One thing to be aware of is that the blade on a circular saw cuts on the upstroke. This means the surface of the plywood that the saw rides on is likely to splinter. So in order to reduce chipout on the “good” side of the plywood, you’ll want to place it face down on the foam.

Reducing Chipout – But many times, you don’t want either side to splinter. One way to reduce chipout is to use a blade that’s specially designed for cutting plywood, as shown in the photo at right.

Another way to produce a clean cut is to make two passes. A shallow, first pass severs the fibers of the surface veneer, as illustrated in the detail in Figure 2. This means the fibers won't splinter when making the second, full-depth pass.

 

Have a nice weekend,

Bryan Nelson
Online Editor, ShopNotes


  To help reduce chipout, these inexpensive, steel saw blades have tiny, razor sharp teeth that remove small amounts of material.  
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