Introduction: Circular Saw Cutting Jig for Vinyl Siding

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About: I'm a husband and father that loves working in the garage. From sewing to welding to wrenching on engines and everything in between.

I recently replaced the old weathered aluminum siding on my house with maintenance free vinyl siding. The cuts can be done by hand with a set of tin snips, but squeezing the snips 5-6 times per cut can get really tiring and leaves a somewhat jagged edge. Even though most of the cut edges will be hidden behind J-trim or corner trim, I wanted a way to cut the siding quickly and cleanly. I created a cutting jig to use with a battery powered circular saw out of scraps I had laying around.

Of course, this jig can be used to get a nice square cut on any material that will slide into the opening.

Step 1: Building the Jig

Tools needed:

  • circular saw
  • framing square
  • drill/driver

The jig is pretty simple, it requires two pieces of plywood (can be same thickness), a couple boards of the same thickness for risers, two boards to use as runners and a handful of screws.

Attach the riser boards to a large piece of plywood. The risers need to be taller than the profile of the material you're cutting. You also need to consider the cutting depth of your saw. I had a 2x4 that had been ripped down to ~1", so I used that for my risers.

I was only using a 5-1/2" trim saw so I opted to use a thinner plywood for my runner support. On the plywood used for the runner, mark and cut the plywood so it has a perfectly square corner. Attach one runner board to the plywood so that it square. Adjust the blade on your saw so that none of the blade protrudes through the base plate. Place the saw on the plywood with the side of the base plate touching the first runner. Put the second runner in place so that it is touching the opposite side of the base plate. The two runners need to be parallel to prevent the saw from binding, so push the saw through the runners to make sure the runners are evenly spaced. If parallel, attach the second runner to the plywood.

Attach the runner assembly to the riser assembly, ensuring that the runner is perpendicular with the riser. Take into account where the saw blade path will be and avoid putting any screws within 1/2" of that area. Once the two assemblies are joined, adjust the blade depth so that it will cut through the runner plywood, the risers and 1/8" deep into the base plywood. Make a cut the entire length of the runner.

To see the cut marks I put on the siding, I cut a small opening in the runner plywood by doing a freehand plunge cut with the circular saw. ***Some may consider this dangerous - if you're uncomfortable doing this, use a different method!!! To plunge cut the sight window, place the front of the saw base on the material to be cut, while holding the back of the saw at an upward angle. Pull up the blade guard. Start the saw and plunge the blade into the material. Cut to desired length and remove the saw. This was a quick and dirty jig, so I just broke off the thin strip that I cut out. You could also use a jigsaw, dremel, or oscillating tool to make this cut, or drill a series of holes and file out as needed.

Step 2: Using the Jig

To cut vinyl siding with a circular saw you can find specialty "vinyl siding" blades, but most people just turn a fine toothed blade around so it spins the opposite direction. This prevents the teeth of the saw from grabbing the material. Once your blade is installed, set the cut depth of the saw so that it is just barely deep enough to get through the material.

Mark the siding where it needs to be cut, slide the siding into the jig so that the mark lines up with the saw kerf in the base plywood, hold the siding tight to the riser to ensure a square end and make your cut. This setup worked incredibly well. Well enough that I actually ended up using a cut end on a visible joint a time or two to minimize waste.

Here's a video of the jig in action to cut some vinyl soffit.