Too tight plywood dado

[ebarker9]

Like the title says, I've been building a tool storage cabinet with dados and I'm struggling to get everything to come together. I've rechecked everything for square, thickness, and depth and it all looks spot on. It looks like I need a little more margin with the one dado joint because it won't come together with clamps or mallet persuasion. I figure I can either do some hand sanding hoping that I don't go through the veneer or break out he stacked dado set and try to do a very careful skim cut at the same depth. Any preferred option or something I'm not thinking of?

[WaterlooMarc]

First choice for me would be widening the dado with a side rabbet plane. If you don't have one of those then I would cut a rabbet on the shelf or crossmember (whatever part is going in the dado). I wouldn't try to widen the dado, too many things to line up and set.

[Ray Newman]

If I read your post correctly, the dado is too tight, and if that is the case, a side rabbet plane easily will open it up to accommodate the stock.

Lee Valley and Lie-Nielson offer them. At one time Stanley offered one.

www.lie-nielsen.com/product/handplanes/side-rabbet-plane-pair?node=4063

http://www.leevalley.com/US/Wood/page.as...&cat=1,41182,48945&ap=1

My SWAG (Scientific Wild Arsed Guess) -- trying to recut the dado with a stacked dado will be tricky.

Have heard that adhesive backed sand paper applied to a piece of stock -- sometimes --can open up dado width if it is not too tight and the dado is shallow and not very long.

[GNP]

Set up the stacked dado with a sacrificial fence. Have the blade sticking out of the fence the depth if your dado. Skim off a few thousands of an inch on a test piece of ply until it slides in your dado. Run the shelve thru the saw and put it together.
edit to add; If I'm using the table saw, I always like to make the piece fit the dado, instead of making the dado fit the piece.

[ruffcutt]

GNP said:

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Set up the stacked dado with a sacrificial fence. Have the blade sticking out of the fence the depth if your dado. Skim off a few thousands of an inch on a test piece of ply until it slides in your dado. Run the shelve thru the saw and put it together.
edit to add; If I'm using the table saw, I always like to make the piece fit the dado, instead of making the dado fit the piece.

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This is what I've done in the past. It works.

[Hoosier25]

Widen the dado cutter on your table saw with a shim. Sound like 1/100 of inch might make it work , use a test piece to check. I wouldn't sand veneer plywood to fit.

Another option is use flat top saw blade(Rip), put against the dado, then add painter tape to side against rip fence to move the blade for fit. Testing is always a good idea, before committing to final cut.


Roger

[Cooler]

I had that same problem recently due to the fact that the two consecutive sheets of plywood at Lowes were of different thicknesses. I set the dados to fit the first sheet and then made some of the shelves from the second sheet.

I like a fairly tight dado, but these were too tight to clamp shut. A few quick passes over both sides of the shelves where they insert into the dado resolved the problem.

Widening dados on the table saw or RAS is problematic as you have to re-set the fence perfectly to get this right.

I really think that thinning out the ends of the shelves is the logical way. You can plane it but if it is just a few thousandths off then the sanding route works perfectly. Be careful not to go through the top layer where it will show though.

[jteneyck]

With plywood it's best to fit the dado to the piece rather than trying to sand/plane down those incredibly thin veneers to fit a tight dado. I use a hybrid version of what was said above when I have to go back and "adjust" a dado. Put the dado stack back on your TS, exactly as you had it before. Lay the piece that needs the widened dado over the blade. Adjust the blade height until it just skims the bottom of the dado - the height is set. Now bring the fence up to the workpiece and clamp it in place making sure you can slide the piece back and forth along it without problems. OK, now add a piece of tape to the fence or end of your workpiece and recut the dado. It should fit. If not, add another piece of tape.

John

[Cooler]

The bottom part of the shelves generally don't show. I would set a cross cut blade to the exact depth of the dado. Put on a tall fence on the table saw.

With the shelf upright set the fence so that it just kisses the bottom side of the shelf where it inserts into the dado. Adjust as required for a good fit. After it is adjusted for the first shelf all the others will be the same.

On an occasion where I made a drawer just a 1/32" too wide I took a similar pass on the sides of the drawer to make it fit. I set the blade to the height of the drawer slides. Worked perfectly. (Not as good as getting the size right in the first place but fully functional and completely hidden.

[Steve N]

I have 2 thoughts that I didn't notice, if someone said them, sorry I missed it.

1) It's plywood, and even though it's manufactured it is not perfect, and edge thicknesses especially are prone to being differing thicknesses. That alone will queer a dado fit pretty quick. Dado is a perfect 3/4, 19 MM, or 23/32, but it's edge is a varied thicker or thinner dimension. Makes it hard to fit the pieces together sometimes, even if you cut the "perfect" cut.

2) I will likely get opposition here based on the answers already given, but I find the "Plywood" sizes for router bits much more to the point then a Dado blade can be made. Consequently I feel you get a better cut, better fit using a dado and an edge guide, or a dado cutting jig than you will on a TS with a dado blade.

3) Cutting errors are easy enough to make. If you are throwing around a 3/4" sheet of plywood, you are unwieldy, and heavy, which is a bad combination to expect accuracy from. at least repeatable accuracy. UNLESS you do this often, then you get good at it. Break all tasks down to 2 types, and you will fail less often. First are those where you bring the work (smaller stuff) to the tool. Second is where you are working with bigger stuff like plywood, and here it works best to bring the tool to the work. So by default using this either or system a hand held router is the choice.

Go ahead, pile on. I can take it


Adjustable dado jig for a router It works so well because it uses the piece you are going to insert into the dado to set the jig


Below Bob shows how to make a build as you go adjustable dado jig. IOW another way to skin this cat. A third way is to just use a clamped straightedge and know your distance from center of your bit to the edge of your straightedge. Any and all of these can be made to be as long as you want them to be. I will say the longer than 4" variety work best with 2 sets of hands.


https://www.youtube.com/watch?v=v0ZUAOJHmHg