How to Make a DIY Circular Saw Crosscut Jig

Hey there friends! Today we’re heading to the workshop for a new DIY workshop plan. We’ll be making a handy little tool… a DIY Circular Saw Crosscut Jig!

After I assembled the lamp base for my Cutting Edge Stencils lamp, there was something “off”, but I just couldn’t put my finger on it what it was. Then it hit me. It was too tall. Despite designing it in SketchUp first, it just didn’t look right in person.

I didn’t have time to build a new one as I was on deadline to finish it. I needed to figure out a way to cut it down. It wouldn’t fit in my miter saw, believe me, I tried. I guess I could have cut it on my table saw, but that seemed a little clumsy, plus if I cut it on the table saw I wouldn’t be able to show you how to make a crosscut jig for your circular saw!

What can you do with a crosscut jig? Well, have you ever needed to cut a piece of lumber that is too big to fit in your miter box or miter saw? You could use a hand saw, jig saw or circular saw, but for me it’s nearly impossible to get a straight cut.

A crosscut jig will allow you to make straight cuts every time. The saw rides along the fence of the jig and keeps your cuts straight and true. Oh, you can also cut angles with it. It’s a handy little tool that won’t hardly take up any space in your small shop. And you can fix a lamp base when you made it too tall!

Here’s a close up of the cut and how the jig works. Place the jig exactly where you want to make the cut and follow the fence:

Let’s get started!

Supplies
Scrap piece of 1/4″ MDF or plywood – approximately 12″x14″
Scrap piece of 1/2″ MDF or Plywood – approximately 3-1/2″x14″
Glue
3/4″ Pin nails
3/4″ wood screws
Circular Saw

Step 1
On your circular saw, measure from the blade to the left edge of the base plate and from the blade to the right edge of the base plate. Add these two numbers, then add 3-1/2″ (width of the fence that we’ll cut in Step 3).

In my case left 1″, right 4″, plus 3-1/2″ = 8-1/2″, so the bottom we will cut in Step 2 will be plenty big enough. The bottom needs to be larger than this total as we will cut off the excess to square the jig in Step 7.

Step 2
Cut bottom 12″ x 14″. Adjust the size if necessary for your saw – If your measurements from Step 1 total more than 12″, add a few inches.

Step 3
Cut fence 3-1/2″ x 14″.

Step 4
Take the short side measurement of your saw and measure in that amount, plus about 1/4″ more. In the case of my saw, I’ll measure in 1-1/4″. This is where we are going to mount the fence.

Step 5
Apply glue to back of fence, position on bottom, check for square, clamp, flip and tack in place from back with 3/4″ pin nails.

Step 6
Pre-drill counter sink holes and secure fence with 3/4″ wood screws.

Step 7
Flip over, using the short side of your circular saw, place saw base plate on the jig bottom and up against the jig fence. Follow the fence and cut to square the jig. Do the same with the wide side of your saw on the other side. The edges you just cut on the jig are exactly where your saw will cut. Now your jig is square and ready to use!

Using the Jig

To use the jig, first measure and mark each edge of the piece you want to cut.

Place the jig on the marks (where you want to cut) and clamp in place.

Then using the appropriate edge of your saw (wide side of jig = wide side of saw, short side of jig = short side of saw) make your cut.

Depending on the cut, sometimes I also add a scrap piece of 1/4″ MDF (same thickness as the base of the jig) held in place with painter’s tape. This extra piece of MDF helps keep your cut square. I used this method to cut down the lamp.