3/4" wide dado how deep? - Woodworking Talk - Woodworkers Forum
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post #1 of 23 Old 04-18-2014, 01:30 PM Thread Starter
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3/4" wide dado how deep?

Using 3/4" plywood to build a router stand- the bottom piece will be 3/4" to connect both sides of the stand together with a dado and pocket holes. How deep should the dado be? 1/4"-3/8"1/2"? And I dont want the pocket holes showing so I am going to make them on the underside of the bottom piece- do you think that is a good idea?
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post #2 of 23 Old 04-18-2014, 01:34 PM
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With good tight fitting dados, likely you won't need pocket screws. Check out my router table build thread in the project showcase....just plywood and glue. No screws at all. My structural dados and rabbets were 3/8 deep, non structural were 1/4

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post #3 of 23 Old 04-18-2014, 05:44 PM
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I agree with the above, with good fitting dadoes, no pocket holes are needed. The advice I've been using is that dadoes should be 1/2 the thickness of your material, so 3/8" in a 3/4" thick board.
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post #4 of 23 Old 04-18-2014, 06:30 PM
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With using dadoes and rabbets I make the depth ". I don't use pocket screws.




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post #5 of 23 Old 04-18-2014, 06:37 PM
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Another vote for no pocket screws. Not to mention, if the panel sits in a dado the pocket screws will most likely end up coming through the outside of the case.
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post #6 of 23 Old 04-18-2014, 08:39 PM Thread Starter
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OK great information yes I was thinking how pocket screws would work because they probably would come through the outside. I am going to make a tight dado 3/8" deep- with glue and a face frame pocket holed on then this should be strong enough. Thanks for the reassurance. I will post pictures when I am done- might be a couple weeks
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post #7 of 23 Old 04-18-2014, 10:46 PM
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Quote:
Originally Posted by aaronhl View Post
OK great information yes I was thinking how pocket screws would work because they probably would come through the outside. I am going to make a tight dado 3/8" deep- with glue and a face frame pocket holed on then this should be strong enough. Thanks for the reassurance. I will post pictures when I am done- might be a couple weeks
Recently, I built a cabinet that didn't turn out right. Dry fit looked OK, but once it was glued, screwed and stapled, it wasn't square. One board (the center divider was a little short and ruined the whole thing. I wound up cutting it in half and recycling it into two cabinets.

3/8 inch dadoes and Titebond glue. I removed all the screws and tried to beat it apart, but gave up! Now part of it is hanging on the wall in the garage. More storage.

The glue is awesome stuff. Go for it.
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post #8 of 23 Old 04-18-2014, 10:55 PM
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Nobody said it just like this so I will. I read that a general rule for dado depth is NO MORE THAN 1/2 of the thickness of the wood the dado is cut into. It doesn't mean it has to be 1/2 the depth, just no more than that. Like Cabinetman said, 1/4" works for him, and I'd imagine he's done that in wood 3/4 thick before so he only went 1/3 of the depth there.

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post #9 of 23 Old 04-20-2014, 12:04 AM Thread Starter
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Spent several hours getting this far- my table saw is just barely good enough for this. The plywood I bought isn't a consistence thickness so had to fool around with the dado stack thin spacers. Overall pretty happy...now I need to buy some clamps to glue it together. Face frame after that then I plan on two small drawers up top and two wide drawers on the bottom.

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post #10 of 23 Old 04-20-2014, 03:49 PM Thread Starter
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When I was glueing up the dados were extremely tight. How much clearance do you still consider a tight fit so the glue has enough room? 1/64? 1/32" There was one piece of plywood that was a hair thinner than the rest and I wanted to make sure all the dados were tight but looks like they were TOO tight
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post #11 of 23 Old 04-20-2014, 05:17 PM
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I've been doing a lot of dados lately and find they should fit in and out without having to drive them together with a mallet.

Long dados are going to seem like they are more tight when going in. If so just take your block plane to the corner edges of the piece going in. It will make it easy to fit it in the dado but you will still have a good fit when it's seated when you glue it in place.

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post #12 of 23 Old 04-20-2014, 05:55 PM
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The piece looks great so far. Don't screw it up with pocket holes!

Building with plywood the way you are gives it lots of strength. Just take a router and make a rabit around the back side and glue a piece of plywood to the back for strength and to prevent racking. Then the face frame only needs to be glued on using half laps at the corners and cross pieces. NO POCKET SCREWS! Please.

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post #13 of 23 Old 04-20-2014, 06:18 PM
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The piece looks great so far. Don't screw it up with pocket holes!

Building with plywood the way you are gives it lots of strength. Just take a router and make a rabit around the back side and glue a piece of plywood to the back for strength and to prevent racking. Then the face frame only needs to be glued on using half laps at the corners and cross pieces. NO POCKET SCREWS! Please.
+1.




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post #14 of 23 Old 04-21-2014, 01:37 PM Thread Starter
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Originally Posted by Al B Thayer View Post
I've been doing a lot of dados lately and find they should fit in and out without having to drive them together with a mallet.

Long dados are going to seem like they are more tight when going in. If so just take your block plane to the corner edges of the piece going in. It will make it easy to fit it in the dado but you will still have a good fit when it's seated when you glue it in place.

Al

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I ended up having to bang in most of the pieces. That is not good and the next project will have a little wider dados. I jsut didn't want it to be very loose but the glue fills in a little too

I will only be using the pocket holes to attach the face frame.
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post #15 of 23 Old 04-21-2014, 01:55 PM
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Banging them in can sometimes cause the ply to split it can also cause the face containing the Dado to not remain true. It can create a slight warp. I tend to make mine tight and simply a 1/32 or so over is ideal for the glue up.. but you do not want to have to excessively force the board into the dado per negative structural results..
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post #16 of 23 Old 04-21-2014, 06:42 PM Thread Starter
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Dry fit was excellent- put glue in there and it was very tight...Wish I could unglue and recut all the dados. Maybe I used too much glue but I will live with it because this is my first big "furniture cabinet" project, have to learn sometime. There is a slight bend in the upper end of the side piece so hopefully the faceframe will fit ok
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post #17 of 23 Old 04-21-2014, 09:48 PM
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AA
If you have a sander. Dry fit and if it's tight run the sander on the edge that goes in. You don't need a lot of glue either.

Al

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post #18 of 23 Old 04-22-2014, 11:20 AM
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When dry fitting a dado, it should slide in snug, and if you pick up the main panel, the captured panel should raise with it. They say about .003" of clearance for the glue.
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post #19 of 23 Old 04-22-2014, 09:05 PM
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I agree with all the other posters, a decent dado, properly fit will not require any other fasteners, pocket screws or otherwise.

The depth of the dado effects both the vertical and the lateral strength of the joint. If the project requires little strength in both directions, a shallow dado will suffice. A large and deep bookcase however would probably need dado's at least 1/3 of the thickness of the uprights if made from plywood. Hardwood would require less.
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post #20 of 23 Old 04-22-2014, 10:38 PM
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Quote:
Originally Posted by EdS
I agree with all the other posters, a decent dado, properly fit will not require any other fasteners, pocket screws or otherwise.

The depth of the dado effects both the vertical and the lateral strength of the joint. If the project requires little strength in both directions, a shallow dado will suffice. A large and deep bookcase however would probably need dado's at least 1/3 of the thickness of the uprights if made from plywood. Hardwood would require less.
I agree. Today I cut dados for dividers. They were 3/4 thick but I only cut the dado around 1/4".

Al

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