shevles - biscuits or dado

[Bob Cooper]

i'm getting ready to build some cabinets and am thinking about how I want to attached some fixed shelves. I don't want to install cleats/runners for the shelves to sit on. The other two methods most obvious to me are (1) using biscuits and having the shelves butt up against the sides or (2) dado the sides and have the shelves sit in the dados. Is one method used much more often than the other? Also...if there's another approach let me know.

[John TenEyck]

Dados are the conventional way, although I've used biscuits for a lot of shelves and have never had one break. A higher end approach is a sliding dovetail, which has the added advantage of holding the sides of the cabinet together. Harder to cut than dados, but still not all that hard. Dowels, internal cleats, Miller dowels, plugged screws - there are all kinds of ways to attach shelves.

John

[Joe Shinall]

Dados to me are the way to go but it depends on what's easier for you and what you plan on using the shelves for. Dados are a good way of strengthening a whole cabinet and helping square it in my opinion. But I have used pocket holes and biscuits before for cheap and easy cabinets and bookcases for stuff like shop use where they didn't need to be perfect. Dados are much stronger also.

[Sam Murdoch]

I have used biscuits, dominos and the dados with good results. Lots depends on how much weight the shelves will support and whether or not you are also attaching face frames. Unquestionably the strongest method that also adds the most to the structural rigidity of the cabinet is the dado method. Here is a link to a post I wrote using a router sled for this application - http://www.sawmillcreek.org/showthread.php?198249-Bookcase-Joinery-Simple-Method-Secure-Joints

[Ken Fitzgerald]

Dados are my favorite for strength and alignment but it really depends on what you plan on putting on the shelves.

[Rick Potter]

Great post Sam,

Why not put it in the tips sticky on top of this page.

Rick Potter

[John Sanford]

Fixed shelves, I'd go with either dadoes (stopped is an option) or sliding dovetails. With sheet goods, definitely dadoes. Solid wood, sliding dovetails are cool, but they can be really finicky.

[Joe Scharle]

I use this jig which allows for exact thickness dados as well as sliding DTs . For sliding DTs, I can set the jig for a taper cut. I made the jig long enough so I can cut dados, then rip the stock for exact mirror image alignment. Exact width dados are very important for maintaining structural integrity of the case sides, because what's left after the cut is the NEW thickness of the side unless the cut is completely filled.

259348

[Bill Huber]

I like dados and if you can cut them before you cut the sides apart you will get perfect alignment with no problem. If you are not putting a face frame on the cabinet then I would use stop dados or 1/4" edge banding.

[Richard Coers]

I stopped using dados years ago. It's difficult to get two sheets of plywood the same thickness, and the thickness can vary across a single sheet. Biscuits are my choice. In some cases, I tape off the biscuit slots, and then prefinish the piece before assembly. When I was in business, I used this construction in the world's toughest possible situation, day care centers. Never had one fail.

[Jamie Buxton]

Either will do structurally, but they're both insufficient for a strong case. They just make the case into big rectangles that can wrack into parallelograms. For strength, the back is more important than the choice of shelf joinery, bacause it prevents wracking.

[Kent A Bathurst]

Stopped/blind dados, with rabbeted/tenoned shelves.

By rabbeting 3/4" shelves to fit, say, a 1/2" dado, you accomplish two things. You get a better "hide" on the actual joint, and you get around issues with the variability in different ply sheets.

The easiest way for me to rabbet is with a 3/8" rabbeting bit in a hand-held router. Make one cut, flip it over, make another cut, test fit. Sneak up on the final dimension, with a tenon that is centered and a perfect fit. You can do the same with a dado head on the TS.

I use the exact same methods for solid wood shelves.

Its a personal thing, but I never liked my biscuit joiner. Less precise, less glue surface area. Sold it.

[Jeff Duncan]

I don't do fixed shelves very often but when I do I use a slightly different technique. It's a bit more work, but I think it's a better way in some respects.....I run a stopped dado in the carcass and then glue in a spline. Then I run the stopped groove in the shelf and slide it on. I prefer this way as if there's any discrepancies in the plywood, (likely), you won't have issues with a sloppy fit;) You also don't worry about having a perfectly sharp dado blade as the edges of the dados are covered up. And lastly it's a bit easier to put together as you can assemble you cabinet and then come back and slide on shelf in at a time!

good luck,
JeffD

[John TenEyck]

I have used biscuits, dominos and the dados with good results. Lots depends on how much weight the shelves will support and whether or not you are also attaching face frames. Unquestionably the strongest method that also adds the most to the structural rigidity of the cabinet is the dado method. Here is a link to a post I wrote using a router sled for this application - http://www.sawmillcreek.org/showthread.php?198249-Bookcase-Joinery-Simple-Method-Secure-Joints

Sam, sorry to question what you say is unquestionable, but what data do you have to support your claim that the dado method is both the strongest and and adds the most structural integrity to the cabinet? I really can't see how a dado could be any stronger than a one sided sliding dovetail, and I would think it offers far less less racking resistance as well. There may be other methods as well. In any case, statements like "unquestionably" really get my attention when they are unaccompanied by data or a link to a publication that substantiates it as true. If you had said, "in my opinion ...." OK, no problem. But "unquestionably" requires confirmation, so ....

John

[Sam Murdoch]

John - I was referring to the 3 methods I indicated as options in my post and that the OP was asking about. Sorry to not have been clear - or more precise. I would not dispute that the sliding dovetail - one or two sided - is structurally a step up. Also, I was not referring to a fully housed dado but rather a stepped dado as shown in the post to which I attached a link.

[John TenEyck]

Thanks for the follow-up Sam. All is well.

John

[Bob Cooper]

thanks for all the replies. Maybe you can give me some advice on the following...I used biscuits but had a hard time getting the two sides to pull tightly together. I suppose I should have built some cauls (which I've never used but understand how useful they can be) and used those to apply an even amount of force. Using clamps I couldn't get really get pressure on the middle to tighten it up. As you can see from this picture the shelves don't go all the way through. This is a small open faced cabinet for glass bowl/pans for a kitchen. in the end I pulled it together with screws -- worked well in this case but not feasible in many cases. Any suggestions?

[Kent A Bathurst]

Dunno what type of clamps you use.........

Depending on the depth of the cabinet, the long-ish clamp surfaces on parallel clamps can get far enough in from the font & back to pull it tight. Plus, parallel clamps will keep the sides.....ummmm.....parallel, so the case comes out square?

Me? I usually use cauls, for the reasons you point out. Somewhere running around here you can find various explanations on making cauls. Mike Henderson did a very good tutorial some time back, using 2 x 4 studs. I made mine with 8/4 HM. There are other examples here also. Whatever - just don't get so wrapped up on the details that you are over-driving your headlights. Rocket science ain't in it. It is worth the time to make a set for this type of work, and also to keep table-tops flat during glue-up.

One last point - after learning early on about the difficulty of pulling joints togather after the glue has started to kick over, I break down my glue-ups into sections. On your photo, I would probably have three glue-ups: Top 2 shelves on the left. Bottom two shelves on the left. Deep breath, go fast, all four shelves on the right. In the first two clamp-ups, I would, of course, dry-fit the right side, to keep everything in line.

[Chris Friesen]

I stopped using dados years ago. It's difficult to get two sheets of plywood the same thickness, and the thickness can vary across a single sheet.

Simplest way to deal with this is to cut a shallow rabbet in the plywood, referenced off the uncut face. That way the thickness of the "tongue" is constant, and any thickness variation is in the depth of the rabbet.

[Ole Anderson]

thanks for all the replies. Maybe you can give me some advice on the following...I used biscuits but had a hard time getting the two sides to pull tightly together. I suppose I should have built some cauls (which I've never used but understand how useful they can be) and used those to apply an even amount of force. Using clamps I couldn't get really get pressure on the middle to tighten it up. As you can see from this picture the shelves don't go all the way through. This is a small open faced cabinet for glass bowl/pans for a kitchen. in the end I pulled it together with screws -- worked well in this case but not feasible in many cases. Any suggestions?

Lay it on it's side and use a BFH. Oops, that was meant for the metal working guys...:p

For woodworking guys, be sure to use a dead blow hammer and a piece of wood...seriously...use cauls.

[Bob Cooper]

Dunno what type of clamps you use.........

Depending on the depth of the cabinet, the long-ish clamp surfaces on parallel clamps can get far enough in from the font & back to pull it tight. Plus, parallel clamps will keep the sides.....ummmm.....parallel, so the case comes out square?


Well i used pipe clamps and i've always wondered why the big attraction to the bessey parallel clamps...seems a little more obvious now.

I will do 3 things going foward to get a little better at this
1) i'll try and build one using dado's and rabbeted shelves
2) i'll build a set of cauls
3) i'll look for oppty to glue things up in stages so that the entire world doesn't have to come together in a storm.

[Don Jarvie]

He's my 2 cents. I use dados for the top, bottom and middle shelf and will add shelf pins between the middle if I want to add some adjustable shelves. Since your using a face frame I would use through dados. If the sides aren't going to show I use some brads to keep it together while the glue dries ala Norm.

To make the dados I use a router. It's more accurate the dado blade in the TS depth wise. To lay out the dados I put the 2 sides side by side with the back edge together like a book. I then measure down from the top and lay out the dados. I don't have a 3/4 inch bit so I need 2 passes. My 1st pass is from the top line so if the cuts are slightly off the top of the shelf will be sq to the side. If the was a slight gap it would be under the shelf.

Ive found the key is to measure from the top for the whole case.