Dado depth?

--------------------------------------------------------------------- Mikey likes 1/4" deep dados for 3/4" thick shelves.

Cut shelves 1/16" short thus allowing 1/32" per side.

SFWIW, the shelves are strictly in shear at the dado end points.

As far as a router bit is concerned, don't you already have a shelf space reserved for that new bit?

Lew

Suit yourself ... almost all of the dadoes/rabbets I cut in ply are 1/4" in depth, but 3/8" is fine in 3/4" thick ply also.

I usually use 1/4" for one overriding reason ... almost without exception I prefer to cut all dadoes/rabbets with one machine setup, as it fosters consistency, which fosters fit and square, and 1/4 allows that, even with dividers and shelves that are back to back.

I'm not sure I get this last bit. Could you flesh it out a little?

You mean, inside the micro-bookshelf? :)

--------------------------------------------------------------- If the inside distance between the verticals is 30", then using 1/4" deep dados, the distance from bottom of dado to bottom of dado is 30-1/2" and the shelf would be 30-7/16" allowing 1/32" per side for slop.

Lew

If instead the dados were intended for vertical inserts(structural), would you anticipate some *slop* in forcing the joints square (and thus rely on an additional mechanism, such as screws or dowel-joinery for more strength). or would you not expect this to be an issue, with plywood. If so, would you (really) add 1/32" to a 1/4" dado cut in 3/4" ply to help account for this? My guess is no, but you raised my curiosity about the way that you approach achieving the desired results--exactitude in the desired height, for instance, the sort of perfection that Swingman has preached to me about!

Bill

A quarter will be fine in 3/4 ply if your fitting a back and framed front .

I would do that for shelves with one or two shoulders but definitely not for shelves without shoulders. With shoulders, the distance between them end to end determines the shelf width and you want the tongue fully within the dado; making the tongues a skosh short assures that the shoulders will be touching the uprights and that tells you visually when the tongues are all the way in.

Without shoulders - I rarely do this - you want all the shelves to bottom out so I make the dados slightly sloppy so that the shelves are an easy fit.

That's what I figured you meant, and that's why I'm confused. Whatever length I cut the shelves, won't the shelves of necessity bottom out in the dadoes during glue-up, whether held in place by clamps or screws? Are you suggesting that the glue will take some extra space, or will swell the wood such that the shelves expand a hair (lengthwise)?

That is a holdover from days of yore that is no longer operable in most situations, particularly the one under discussion.

Cut it the exact/proper project dimension and be done with it ... if you don't batch cut, or if you use only hand tools, you will have at least a

If you are working with modern tool and take reasonable care to properly use consistent reference edges and proper machines techniques, and unless there is a specific reason and/or you are simply that damned sloppy, there is generally NO need to build in any "slop" into a dimension in the circumstance under discussion.

Lots of "French model" advice on the Internet these days confusing you ... beware, and bawn jyour.

If you ignore Lew you will be better off.

That's what I figured you meant, and that's why I'm confused. Whatever length I cut the shelves, won't the shelves of necessity bottom out in the dadoes during glue-up, whether held in place by clamps or screws? Are you suggesting that the glue will take some extra space, or will swell the wood such that the shelves expand a hair (lengthwise)?

-------------------------------------------------------- Not if you factor in my brain fart.

Forgot to include description of "shoulder" on end of shelf.

See dadiOH post for explantion.

Lew

Simple question to ask yourself. Would you force a 1/32" glue gap between two board edges when making a wider plank? Then why on a dado?

Mair Cee Bo Koo.

I figure myself for a fairly bright guy, and one of the things fairly bright guys do (on those chance occasions when their egos don't get in the way) is consider that other people may know things that we don't. So no, I couldn't think of a reason why one would leave a gap, and in fact, couldn't figure how it might even be accomplished. Hence my puzzlement, and my question.

I try to weigh the advice I get here against my own sense of how things work. I also weigh responses against each other. So fear not, my cabinets will not be 1/16" too narrow. My mistakes are seldom that small. :)

Quick, TradeMark that before some RAP group locks onto it, then used to name a future NFL running back ...

Responses are easy to come by ... responses with actual hands-on experience factored in, not necessarily. Some folks even try to make it easy for you to take that into account. :)

I prefer to envision the overseer of a town in Senegal (wait for it) "Mayor Siboku"

:)