Dado depth and how tight?

[Henry Anthony]

Greetings all,

I'm new to the forum and relatively new to my TS2424 although I have owned it for 2 years. I am building some simple bookshelves from oak plywood and my questions are:
How deep should the dado be? I'm thinking 1/4-3/8 but I would love to hear what you all think.

Also, how tight should the joint be? I have a Freud Super Dado. The 3/4 set-up was way too loose. With the chipper for undersized plywood I need to really hammer the pieces together (scrap of course). Should I really want a joint that tight?

I am going to try a shim tonight and see what happens.

Thanks in advance for your opinions. I really need your help as my wife is going to hammer me if I don't finish those bookshelves [img]redface.gif[/img])

Best regards,

Henry

[boyoak]

3/4 plywood is actually 23/32" so use the two outside blades, and the two smaller chippers, then add a shim or two, depending on which ones you use. I like the depth to be 1/4". You should not have to beat the parts into submission. Sometimes, plywood warps and even with the perfect setup, it needs a bit of coaxing to come together.

[daveferg]

Henry----I was taught to make the dado depth up to 1/2 the thickness of the stock (i.e. 3/8" for 3/4 stock), but since then, I've seen many people sware by 1/4" and even one mag' said 1/8"----believe who you want---I generally stick with 3/8, 5/16 or occassionally, 1/4 inch for 3/4" stock.

As to thickness----today's plywoow makes this a lot of fun, since it doesn't even have the same thickness at two different parts of the same sheet--

Anyway since you're starting out with your new dado set and will be experimenting anyway, here's something I read that will later save you scads of time.

Take a good, unwarped piece of 3/4" solid wood or cabinet grade ply'----maybe 6" wide by 16" long. Now, when you set up your dado stack---make a sample cut on this board, about 5/16 to 3/8 deep and next to the cut, mark down which chippers and shims you used----do this with other combinations---then, to cut a snug dado---just take your gauge and try out the groves until one fits and install the listed chippers/shims you used.

[UO_Woody]

Dave;

I'm glad you suggested that. I got scrap pieces of ply all over the place, and fight remembering what I used last time! (friend gave me a new kick name the other day...Ply-Woody)

Blows Hero's Buggle

[daveferg]

Yea---I like it too and could build a house with all the scrap ply' lying around.

Saw somebody on some thread where this idea was posted----said if you go the time to waste, go ahead! Couldn't be any more time than I waste trying to get a tight dado!

BTW----plywood is the toughest for snug dados, as said, because of slight variations on thickness---always cut dados on the shy side---nothing more useless than a sloppy dado----If I run into a problem, I use my low-angle block plane or a sanding block---on a shelf (part going into the dado), where it won't show, and holding the plane/block out, just trim until I get a good fit---never takes too much.

[Vigs]

Just curious, doesn't anyone use biscuits
instead of dados?

[Charlie P]

I use a ton of biscuits to align and perhaps strengthen the joints when I am gluing up panels. I even use biscuits on many miter joints, much like a spline. But when I am putting a shelf in a cabinet or bookcase, I want LOTS of strength, beyond the glue but-joint, and beyond the relatively thin piece of biscuit, so a dado is the way to go.

I was taught to use a dado depth equal to half the thickness of the wood - 3/8 inch in 3/4 plywood. But if you have dados on both sides, you have just cut all the way through the wood. So I switched to 1/4 inch dado in 3/4 inch plywood. The strength still seems fine, and I have more confidence about the strength of the sides, whether cutting from one side or from both.

[Dave Arbuckle]

Vigs, it just depends. Sometimes, you can't use a dado. For example, in this bookcase the shelves butt directly into the sides. Making a dado was (a) unacceptable risk, as I had just enough of this expensive material to make it, (b) problematic in the design, as the edgebanding is 1/40" veneer, and (c) not terribly strong, as the material is 1" MDF veneered.

The outcome is, the bookcase is biscuited together. It isn't as strong as it would be dadoed, but it is amply strong for it's use.



Dave

[Henry Anthony]

hmmm... I posted this over a year ago. Has this thread been resurrected or is the server changing the dates of the replies.

Best regards,

Henry

[Dave Arbuckle]

Someone responded to it, which brought it to the top of the list.

How'd your bookshelves come out?

Dave