Cutting dados and grooves in wood can be tricky sometimes.  Especially when you have 2 or more that need to be evenly spaced apart; even more so when the material you are using is big and rather cumbersome to be run across a dado blade on the table saw; or in my case, both.  I had to make 9 evenly spaced, 1/4″ wide dados in a 4′ x 8′ sheet of 3/4″ plywood.  Way too many dados to measure each individually and remain accurately spaced, and at over 60 lbs. per sheet, I needed a better solution.  My answer to that is a simple router jig to evenly space dados and grooves.  So simple, it only took me about 15 minutes to make, and I built it entirely of scrap material I had laying around.  My plans are to make another version in the future that is adjustable, but for this particular instance, it worked out real well.  It took me only 10 minutes to make nine 48″ long dados.  Making things even easier, if you are using it for narrow pieces, you can build just the first half of the jig and that should only take 5-7 minutes or so.  With many things I make, complexity seems to make it’s way into the equation.  Not with this router jig.  Let’s take a look on how I made it.

 

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I started the jig with 1/4″ thick MDF.  Cutting a strip just a hair larger than 1/4″ wide.

 

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After some light sanding, I fit it into a test slot I made earlier with the spiral router bit I was going to use to cut the dados.  The MDF should be fairly snug, yet be able to slide in the dado without any wiggle side to side.  Take your time with the fit on this.  It ultimately decides how accurate your router jig is.

 

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I cut another piece of the 1/4″ MDF to act as the base for my jig.  I did this on my table saw sled.  You can cut this however long you want but I wouldn’t recommend going anything less than 12″.

 

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Glue the runner to the base piece using some simple wood glue.  It doesn’t matter if the runner is perfectly parallel to the edge at this point.  In fact, I exaggerated it being off to show how the squaring step works later.  However, you do want to make sure the runner is straight and true.  It is a rather thin piece and can flex or bow.  Place a straight edge alongside it to ensure it is nice and straight.  Press it down firmly, making sure to get good contact and to keep it from sliding around.  Add some weights to it and let it dry.

 

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Let the glue dry for 20 minutes or so.  At that point the runner should be secure enough to not move while you use a card scraper to clean up any glue squeeze out but not set up enough to where you can’t scrape it off.

 

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Cleaning the glue squeeze out is crucial if you want the jig to register in the slot properly, and later slide in the dados and grooves you create.

 

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I used a piece of plywood that I knew to have two parallel edges as a guide.  With this guide piece against the fence on one edge and it resting on the jig runner on the other I could pass it through the table saw.

 

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Flipping the piece around and omitting the guide piece, I ran it through the table saw once again.  Now both longer edges are parallel with the runner.  This leaves you with a trapezoid shaped piece.

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Squaring up the ends is made easy on the table saw sled.

 

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I made sure to reference from the same edge of my router base each time.  Even if you believe your router base to be completely centered around your bit, it is just good practice to get into.  Referencing from the same surface each time cuts down your chance of error.  Now let me talk router bases for a minute.  You can see in the picture that I have a black plastic base attached to my router with 4 screws.  If these screws are even slightly loose, that black plastic plate has some wiggle room.  I made sure that the black plate was slid completely in the force direction I was going to be using the jig and tightened the screw securely.  Again, trying to eliminate all room for error.

 

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Taking the jig back to the table saw I ripped the jig down to size leaving it ever so slightly oversized.  Each router is different so you will need to measure your exact router.  Sneaking up on the cut like this will hopefully keep you from making it too small.

 

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After making a test dado, you can see  I am about 1/32″ over to get my desired distance of 2 1/2″ between dados.

 

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So I can then trim off the 1/32″ from the jig.  If your table saw fence is not that accurate, you can always sand away the material to get you where you need.

 

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Once I had the jig trimmed down, I was right where I needed to be.

 

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Use a straightedge to establish your first dado.  I used a speed square to make certain my first dado was square to the plywood’s edge.

 

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Once the first dado is made, insert your newly created jig into the dado and use your router to make the second cut.

 

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Then it’s just a matter of making more dados, each time moving your router jig runner into the next slot.  At this point the router moves along the stationary jig.

 

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Continue until you reach the desired number of equally spaced dados.  If you are only looking at using this jig for pieces narrower than your jig you are pretty much done.  I had some bigger project pieces in mind so I took the jig one step further and made it so the jig moves with the router.

 

 

 

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I cut some more 1/4″ MDF to surround the router base plate.  This was going to keep the router from moving along the jig and make the jig move along with the router.

 

 

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I used some 2P-10 CA glue to edge glue my surround pieces to the jig.  The almost instant bond helps speed up the process and I don’t have to worry about clamping the pieces tightly around the router base.  Just finger pressure for 10-15 seconds gets all my pieces locked in place.  I put some wax paper under my glue-up to prevent it from sticking to the substrate underneath.

 

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After sanding and squeeze out flush with the surface, I added some support pieces to bridge the glue joint just for some extra strength.
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Being the jig was now going to ride in the dados, I tapered each end of the runner using some sandpaper.  If your jig doesn’t slide nicely in a test dado at this point, lightly sand the sides or the runner until it does.

 

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Apply some paste wax to the entire base focussing on the runner.  This will help the jig slide smoothly in the dados.

 

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I needed nine 48″ long dados in a sheet of plywood for the hardware organizer I am making.  The plans call for a 3/4″ plywood top and then the dados needed to be spaced 2 1/2″ apart from one another.  So I needed to add that 3/4″ into my calculation on where to start making my dados.

 

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I made my marks in from the edge of the plywood and drilled a 1/4″ diameter hole approximately 1/8-1/4″ deep.

 

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Then with a 1/4″ straight bit in my router, I inserted the bit into the freshly drilled hole.  I could then clamp a straight edge tight to the router base.  I repeated the same on the other end of the plywood.  I went back and fourth a few times just to make sure everything was lined up properly and everything was good and secure.  This was the first dado and the more accurate it is done, the more accurate the rest will be.  I used a straight bit in the router to line everything up because its strait blades reference the 1/4″ hole accurately.

 

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For the actual cutting of the dados, I used a 1/4″ downcut spiral bit.  I chose a down cut bit because of its cleaner cut and possibly my OCD nature.  You need to slow the router feed rate because the wood chips don’t clear like an upcut spiral bit but the overall cut was cleaner with a lot less surface tear-out.
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The newly augmented jig slides in the previous dado with the router, making it able to do large sheets of plywood such as this one.  Also, the router is set in place now and can’t wander off the line.  In either jig configuration, try to some apply pressure towards the original dado.  That way if your runner has any slop or play to it, the dados stay nicely aligned.

 

Dado-Router-Jig-35Make a dado and move the jig into the next for easy, accurate, and repeatable dados and grooves.  I have to say, I really love this thing.  With all these dados cut, I can finish working on my hardware organizer.  Subscribe to my email newsletter if you aren’t already so you don’t miss a thing.

 

THANKS for stopping by and let me know what you think in the comment section below.  If you have any questions I’d be more than happy to answer them.  If you liked this project, do me a favor and share it on your social media and with your friends.  I will see you guys on the next one!

 

-Nick

 


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14 Responses

  1. Ray

    Very cool idea… Thanks for sharing it with us Nick. It still surprises me when the simplest of ideas turn out to be the most valuable. Nice!

    Reply
    • Nick

      no problem, thanks for checking it out – I always love simple!

      Reply
  2. Steve Gronsky

    The “my o my” written with ca glue caught my eye!!!!!

    Reply
  3. Mark

    Yet another helpful jig/hint from you! Thanks Nick, keep them coming…

    Reply
  4. Patrick Testerman

    Nice simple jig! Just a thought on your plans to make it adjustable: separate the square frame that holds the router from the piece that has the runner that slides in the previous dado. You can cut slots in the two reinforcing top pieces and attach it to the runner base with screws. To adjust the first slot ¾” over, simply put a piece of ¾” stock between the router frame and the runner base. You could also put measurement marks on the runner base to line up with the reinforcing top pieces for quick measuring. Then just make different runner bases for each of your respective straight bits you plan on using to route dadoes.

    Reply
    • Nick

      sounds like an interesting idea – I hope I can show my design sooner than later

      Reply
  5. Jason D.

    Thanks Nick! Great jig and video as always! I actually need to do a similar operation myself except the 1/4″ dados will be used for vertical dividers. However I realized the width of the plywood from the box store is a bit undersized and debating whether I should get the 1/4″ bit of a 3/16″ bit? It would be great to do a test fit, but would rather just buy one bit as needed. Wondering if you ran into a similar issue and/or is a looser rather than tighter fit preferable? Thanks Nick and love all your videos!!!

    Reply
    • Nick

      testing it would probably be the best way – maybe your can measure the plywood more precisely and find a closer matching bit – another option would be to get a slightly undersized bit and rabbet each side of the vertical dividers on each end for a nice friction fit

      Reply

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