Shopsmith Forums

One of the Cardinal Rules of woodworking is "Thou shalt not glue cross-grain." Yet, today I found this comment on a woodworking blog: "Glue works fine in dadoes, any way the wood is oriented. Whether it's plywood or solid lumber." Waddya think? Is it OK to glue, for instance, solid wood shelves into dadoes cut in the solid wood sides of a cabinet or chest?

OK, here is a reply to my own question...After further searching, I found this bit of woodworking lore: "You always need to accommodate wood movement. The shelves will grow and shrink across their width. If they were dado'd/rebated to side pieces of solid wood, as in a bookcase, both shelf and support would move the same amount and there would not be a problem." That sounds right to me...If the shelf and the side are the same width they should move together...make sense to anyone else?

I do this on a regular basis but maybe I don't count because I do not experience all the same environmental changes.

If you dadoed the sides of a bookcase and did not glue the shelves, how else would you secure them?

I have always been advised to only glue the front short piece of the shelf and leave a small free amount at the rear so the shelf stays constant at the front for appearance sake by can still move if it wants to.
Forrest

Your second post is correct. Cross grained gluing refers to the expansion of the parts. As an example, gluing up a table top on the long grain and then installing end caps (breadboard ends) on the table would require using oversized screws and only a small amount of glue at the middle of the end caps. Another example is attaching a table top to a table frame where figure eight clips are used to allow for wood movement.
Bill V

I think the answer to that issue depends on many factors. I have made rabbited joints on solid wood drawers for instance for fourty years and have never had an issue. We are talking hundreds of units and mostly in Carmel and Pebble Beach which is a particularly nasty environment for moisture. I think the newer glues have helped quite a bit. Another factor is the type of wood. Some woods move more than others. An example would be pine vs teak which are on both ends of the spectrum. We used mostly Honduran mahogany for drawers which is probably somewhere in the middle. I still prefer it for drawers today. The expansion and contraction of the wood coupled with the older glues were the reason jointery like dovetails were a necessity. A very good solution in todays world is to cut a very shallow dado ( 3/32”) and then use biscuits to glue it all together. A more traditional method and very classy way to connect shelving to the case is to use the dovetail method which is fairly easy to do with a router and jig. That method allows for wood movement and always lends a great look to the project.
Paul

dusty wrote: If you dadoed the sides of a bookcase a did not glue the shelves, how else would you secure them?

That is the question...I like forrest's take on it...that is how I have attached the side pieces of crown molding on cupboards...glue only the front third or so and fasten the balance with nails...the nails flex enough to let the molding move, but the mitered corner at the front stays tight.

The issue came up because the plans I am using for a china hutch call for gluing the full width of the shelves into the dadoes in the side pieces, as well as using a few finishing nails.

Thanks everybody for your thoughts.