Make a Simple Spline Jig





Introduction: Make a Simple Spline Jig

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This project began with me wanting to make a picture frame. I was doing some research on how I wanted to reinforce the mitered corner joints and that's when I realized something. The corner splines I often see people use on decorative boxes and picture frames aren't just decorative. They actually make the mitered joint much stronger! I knew then and there that I had to start by making a spline jig for my table saw.

Watch the step-by-step video, or read on!

P.S. Be sure to watch the video to enter the GIVEAWAY draw!

Step 1: Make a Box for Your Fence

The jig starts by making a box that will slide snugly on your table saw's fence. I started by measuring the height of my fence. I however noted that the top of the fence had some screws protruding, so I made sure to consider those in my measurements. I cut 2 strips of scrap 3/4 birch plywood to that height, about 10 inches long.

I placed the freshly cut plywood strips on each side of the fence, then measured the total width. I then cut a third strip of birch plywood to this width.

Lastly I glued and screwed the pieces together, making sure the box would slide freely back & forth on the fence while being snug.

Step 2: Make It Bigger

Since I will be using this jig mostly for picture frame splines, I wanted the face of my jig to be large enough to accommodate this.

I found another piece of 3/4 plywood roughly 12x12 inches that I glued and screwed to the front face of the fence box I had just made.

Tip: Watch where you place the screws... read the next step first!

Step 3: Add the 45 Degree Supports

I started by finding the center point of the face at the bottom. I then used my speed square to trace a line at 45 degrees on each side of the center line.

Next I cut a piece of scrap wood in half at 45 degrees using my miter saw. Before I fixed it into place, I did two things:

1. I marked about 2-1/4" from the bottom of the jig. I wanted to make sure to leave this unobstructed space so my saw blade could run freely into my work piece.

2. I clamped a carpenter's square along the 45 degree markings I had made. This served as a guide to help glue and screw the scarp supports into place.

Step 4: Using the Jig

To use the jig, simply place your frame onto the supports and clamp the piece to the jig.

Visually align your fence so your blade will run through the middle of the width of your picture frame.

Raise the blade to the desired height. Turn on the saw, push the frame through the blade, then turn of the saw. Repeat on all 4 sides.


If you haven't already, watch the video and enter for your chance to win the GIVEAWAY!

P.S. in my next project, I'll be making a picture frame with corner splines. Be sure to check back next week, or subscribe to my newsletter to be notified of new projects as they come out!



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    You might also want to make the splines before cutting the frames. With your setup, the cut is as thick as the blade in use. You might want to look at a dado blade or a full kerf sawblade and think of how to cut the slots to fit your splines.

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    Also look at the "Freud Box Joint Cutter Set, Cuts 1/4 In. and 3/8 In. Joints (SBOX8) set. They are marvelous and cut a fixed width (in this case) spline slot you can repeat with confidence allowing you to cut the splines before or after you cut the slots. They also work well for box joints ;) !


    When building a jig that rides along the table, consider rounding the edges of the jig front and rear so they do not 'catch' on the table (as we hear at 4:10- 44:12 in the video) You might trim the bottom of your jig a sixteenth to eliminate it riding on the table entirely.

    Fence issue: You may want to adhere a piece of material (wood, plastic laminate, etc.) to each side of your fence (or just to the left side) so the face of the fence is a consistent thickness. You might be able to use a clamp to squeeze the front edge a bit to remove the 'bulge.'

    However, as the guide built is intended to keep the work perpendicular to the table and co-planar to with the saw blade, you might consider using two pieces of 12" square plywood joined at a right angle (Use half-inch thick plywood or MDF) with the diagonal braces (thinner is the better) mounted to the inside of the vertical board.

    Note, too, that the jig does not need to run completely through to cut the corner as required. If, after assembly, you lower the blade beneath the table, then set the jig in place with the center if the jig over the saw blade opening and hold the jig tight to the fence. Then (with the saw running) raise the blade up through the jig until it cuts through the jig to the desired distance/height - plus a bit. With the saw running, slide the jig through the blade until the blade passes through the 'v' in your jig and turn the saw off.

    Now, when using it, raise the saw blade to the desired height, put the jig in place on the saw, set the piece to be cut in the jig, then holding piece and jig, push them through the blade, stop the saw and repeat three more times.

    DO not pull the jig back through the blade after the cut is made, It is dangerous, and likely to alter the dimension (thickness) or registration of your spline cut.

    Note: Using a jig that registers to the table saw surface, you may be able to clamp a board to the saw to serve as a guide.

    Subscribed and commented on your vid. Thanks for sharing (and providing a chance to win a great product)!

    A spline is an easy way to make a solid miter joint. With the jig set up so the frame passes at an even 45 degrees over the blade, the spline will extend an equal length on either side away from the corner. The higher the blade, the deeper the cut, the longer the spline extends. If the frame is set up at a different angle, the cut will be uneven, shorter on one side, longer on the other side of the frame, can be a nice decorative effect. On thinner frames, I use one spline, near the center of the wood. On thicker frames, maybe thicker than an inch and a quarter, I will use two splines, each about a third of the way through.

    I can't wait to see this in action. This is a great video. Thanks for sharing.

    That's an awesome and easy to do this. Thanks MUCH.. A newbie setting up my shop now.