Best Way to cut Dados in Plywood

[Adam Slutsky]

I am wondering the best way to cut dados in plywood. I am putting some cabinets together and want to cut some dados in the cabinet sides to accept fixed shelves. Should I make a jig for my router (a fence that lines up with the slot) or should I make the dado on the table saw? I am thinking that it would be easier to do with the router due to the size of the pieces. Any ideas on this and/or how to construct a jig for the router to do it?

[Rod Torgeson]

Adam.....I made all the cabinets for my house and I used the router for all rabbits and dados. It just seemed to be a bit easier using the router. I did make most all the shelves in my cabinets adjustable.

Rod<---in Appleton, WA

[Matt Mutus]

Any ideas on this and/or how to construct a jig for the router to do it?

Build a router table surface (doesn't have to be fancy) or clamp a straight egde down as a guide.

You can also buy a router guide kit from eurekazone, or sometimes your router manufacturer will have accessories for this too.

[Joe Chritz]

Router cuts perfect dados and a jig is really easy to build. A fancy jig allows adjustment pretty easy and only needs two clamps.

I did dado sides on the last kitchen and used two guides clamped to the plywood. Essentially a straight piece of 3/4" ply glued to a piece of hardboard.

A dado sled like a cross cut sled is faster and just as accurate but much more involved to build and store.

Joe

[Dave Falkenstein]

I have cut lots of dados on my table saw, router table and using a hand-held router. The basic decision is how hard (or easy) it is to handle the material.

If the pieces are large (or long), I typically use a hand-held router. I own a Festool Multifunction Table and a Festool router, so I cut the dados on the MFT using the router on the guide rail. One nice thing about this method is that I can cut matching side at the same time easily. Also, pushing the router down and into the cut results in a consistent depth of cut.

If the material is easy to handle, I use the table saw. I attach an auxillary fence to use for positioning the material relative to the blade. I use a miter gauge to guide the material through the dado blade, using a Grr-Ripper to hold the material down on the table.

I use the router table less frequently. But that's just me. All three methods work well.

[Adam Slutsky]

I've seen home made jigs designed for this. They are usually two fences that guide the router accross the wood. The fences are designed so that they line up perpendicular to the length of the board and are usually adjustable. there is one in a book called Danny Proulx's Shop Made Jigs and Fixtures. It seems like it might take me two days just to make the jig. Of course I could also just clamp a board to the plywood to act as a fence and be done! Any ideas on building such a jig. Has anyone built one that works well.

[Adam Slutsky]

Thanks Dave. My pieces are large so the hand held router seems like the way to go. When I win the lotto I will definitely buy some Festools but untill then, I have to go with my old Makita router and lots of home made jigs.

[Adam Slutsky]

So you basically made a fixed size fence/guide? Is that correct? It sounds like I could make up something that the plywood would slide into and then get clamped down.

[Rob Bodenschatz]

I use the same criteria as Dave. Depends on the ease of handing the material. When I use a router, I use a jig similar to the one Glenn built here:

http://www.sawmillcreek.org/showthread.php?t=46406

[Adam Slutsky]

This is exactly what I was looking for!!! Only problem I see is that my router (Makita 3612BR) doesn't have a collar. Maybe I can use a bit with a guide on it with a similar jig. Any ideas?

[Larry James]

Router cuts perfect dados and a jig is really easy to build. A fancy jig allows adjustment pretty easy and only needs two clamps.

I did dado sides on the last kitchen and used two guides clamped to the plywood. Essentially a straight piece of 3/4" ply glued to a piece of hardboard.

A dado sled like a cross cut sled is faster and just as accurate but much more involved to build and store.

Joe
Joe suggested a jig that is easy to make and accurate for cabinet size plywood.

Use SMC search feature (button at top of page) and search Google or SMC for "router dado jigs."

There are plans in magazines, router books and many web sites - from simple to elaborate.

Larry

[Scott Velie]

Don't use just any bit in the router. I get the cleanest cuts with a downcut spiral bit. If I am really concerned about chipout I will also tape the cut line with masking tape.

Scott

[Jim Becker]

This is largely a personal preference issue as well as a practical one. Some of us actually use both methods (router and TS) depending upon the situation and other setups already in use in the shop. For grooves on long stock or rebates along an edge, I tend to use the TS. For crosscut dados, I typically use the router. (but in my case, the router is being guided by the Festool MFT fence)

[Adam Slutsky]

Jim - I'm going to be cutting cross cuts so I'll be using a router and making a jig. I saw the jig that Glen Bradley posted and it looks like the one I'd like to make. However, my router (Matika 3612BR) doesn't have a collet. Are there router bits with guides on the top portion of the bit? The only router bits I've seen with guide bearings have the bearing on the bottom of the bit.

[Alan Trout]

I use my radial arm saw for many repeated cross cut dado's. However I still prefer my large router table for most of my dado's or rabbits. I will also use a hand held router with guide or jig for certain jobs. I like a bit that was ground with down shear and almost never have any issues with tear-out. If I had only one tool for dado's and rabbits it would be the router in some configuration.

Good Luck

Alan

[Dave Falkenstein]

...Are there router bits with guides on the top portion of the bit? The only router bits I've seen with guide bearings have the bearing on the bottom of the bit.

Can't you buy a base for your router that works with PC collars?


Template bits have bearings on top, like these:

http://www.holbren.com/manufacturers.php?manufacturerid=3&catid=66

Not sure I'd cut dados with a template bit, however. Check that out before buying.

Here's another interesting bit:

http://www.woodline.com/c-33-bearing-guided-dado-cutters.aspx

[glenn bradley]

This is exactly what I was looking for!!! Only problem I see is that my router (Makita 3612BR) doesn't have a collar. Maybe I can use a bit with a guide on it with a similar jig. Any ideas?

First let me say that on larger boards I always prefer to bring the tool to the board. Although the jig I built uses a collar and I feel this is easier and more consistent, the original jig I stole the idea from used the edge of the router plate as the guide. The trick here is to put a mark on your router so that the same point on the plate rides the guide edge for the whole cut. My previous jig worked this way.

The build would be about the same except you don't need the collar shelf and the jig would need to be wider to allow for the router plate riding 'inside' the guides as opposed to on top of them. The reason I redesigned it was I wasn't getting adequate support for the router and did not feel confident while making the cut but it was definitely workable.

[glenn bradley]

Jim - I'm going to be cutting cross cuts so I'll be using a router and making a jig. I saw the jig that Glen Bradley posted and it looks like the one I'd like to make. However, my router (Matika 3612BR) doesn't have a collet. Are there router bits with guides on the top portion of the bit? The only router bits I've seen with guide bearings have the bearing on the bottom of the bit.

There are top bearing bits commonly called pattern bits. They will not be spiral but in your case you will have to trade one advantage for another. I went with a 3/8" bit as it meets most needs and had to be consistent for the jig. If you build a different style jig, I would use the largest bit diameter that would allow two passes. Maybe something like:

http://www.holbren.com/product.php?productid=186&cat=0&page=1

[Adam Slutsky]

Thanks, I think I'm set. I'm going to build a jig similar to yours and buy yet another router bit!

Thanks to everyone who helped me with this.

Adam

[Joe Chritz]

I thought I had a pic but I couldn't find one.

What I use doesn't use a guide, just a regular base and a straight bit.

Take a piece of hardboard about 10" wide. Glue and pin a straight piece of 3/4 plywood about in the center. Just so there is a tad more than from the edge of your router plate to the center. Once dry run the router down the hardboard, base against the plywood. You now have a zero clearancer router guide. Make a second one and you can clamp one on you line, stick a piece of scrap between the second one and a small piece of shim stock (I used old playing cards last time) and clamp the second. No way to mess up the dado unless the jigs slip, plus it fits perfect everytime.

With fast action hand clamps it is faster then it took to type this. Plus it is all scrap material to build normally.

I will take a pic after lunch but won't be back in until dinner time to post it.

Joe

[Dwain Lambrigger]

Adam,

I just fininshed a toybox and entertainment unit using 3/4 inch oak plywood. I made a few purchases to do this, as I am a beginning woodworker, and they made my life a lot easier.

1. An adjustable "all in one" straightedge clamp
2. All in one router plate attachment
3. Woodcraft 23/32 (could be wrong on the size) flush trim router bit. They bill these as "plywood" router bits

These cost me about 70 dollars all together, but I only have to cut the dado once, and it is perfect for the 3/4 ply dado, and with the router plate, the bit cuts smoothly through the wood. Also, the clamping straightedge is great for several purposes. I won't be buying a dado blade for a while as this setup works really well for me. As was said by woodworkers better than me, there are a lot of ways to do this, but this way works perfectly for me.

I hope this helps, and good luck!

[Adam Slutsky]

Dave: Why wouldn't you cut dados with a template bit? I can get another base plate for my router - I think Lee Valley even makes a gadget that will allow it to accept a guide bushing. I've considered purchasing it. But then I have to wait for that to come in the mail and the additional cost etc etc.

[Jesse Cloud]

If you go the router route, butt the two sides of the carcass together and cut both sides with the same setup. Guarantees same location on both sides and lessens chance for errors.

[Danny Thompson]

Here is the dado jig I built for my router. It does not require a bushing.

I ripped one 12"-wide and two 2"-wide x 4' long section of 1/2" plywood. I glued and brad-nailed one of the 2" strips to the 12" panel, approximately 2" from and parallel to the edge.

I then put my router against the 2" strip near one end and glued and clamped the other 2" strip so the router base was fit snugly between the two strips. I repeated this process on the other end and tested my alignment along the full length to ensure there was no wiggle room. With everything lined up, I brad-nailed the 2nd 2" strip in place.

Then I closed the ends of with two 2" wide strips of 1/2" ply custom fit to fill the gaps.

Last, I installed my 3/4" straight bit in my plunge router, clamped the jig to the bench so the target slot area was off of the bench, dropped the router into the jig, plunged, and routed the 3/4" slot for the full lenghth.

That's it. Now, to cut a dado, I sandwich the workpiece between the jig and my workbench, align, clamp, plunge and route.

[Bill Huber]

You really don't have to build a jig to cut dados with a router.
I have a jig now the Accurate Guide that I bought just for cutting dados, but they don't make it anymore.

Here is the way, if I remember right, I cut dados in plywood before I got my jig.

To start as was stated if you can put all the parts together and cut them at the same time is best, you know they will be lined up just right.

Use a straight edge, I used an All in One clamp, clamped to the board.
With a down cut spiral router bit of 1/2 in., make the first cut with the normal base plate of the router. The down cut bit makes a very clean top edge.
Now lay a spacer that has been cut to the thickness of the plywood minus the 1/2 in router bit, and make the second cut. Now if the fit is a little tight you can shim the spacer out with a playing card or just make a spacer that is a little wider.

78638

[Dick Bringhurst]

Adam, they make router bits that will cut dados to fit standard plywood thicknesses. this would eliminate the need for the jig. Dick B.

[Adam Slutsky]

Simple enough! I guess I could add another piece below and perpendicular to the slot so that it would be easy to line up the jig and the plywood.

[Adam Slutsky]

yes, but I still want to use more than a straight edge since I'm prone to screwing things up. Also, from what I've read in this forum it seems all plywood is not created equal and thicknesses vary. I like the idea of setting the jig based on the thickness of an existing piece of plywood.

[Joe Chritz]

Here is a quick pic of what I have been using. Obviously it would need to be clamped down with some hand clamps of some kind.

Not fancy but pretty fast and infinitely adjustable.

Joe

[Danny Thompson]

Adam,

Good idea about the strip on the bottom to help keep it square. I forgot to mention that I sanded the edges smooth and hit the inside edges of the 2" plywood strips with a little wax to ensure smooth operation.

[Adam Slutsky]

Thanks Joe: I plan on making something in between this and the more elaborate cousin with the collet guide. I'll post pics when done.

[Dwain Lambrigger]

Adam,

You can certainly go that route. I got all three of the items listed at Woodcraft. In the store.

Good luck with whatever you choose.