How do I tighten this joint on the lid?

[Brian Knodel]

The diagram below shows how a small box will be built. The corners will all be mitered and both the top and bottom will be floating panels. The whole thing will have to be glued up in one sitting and there will be no access to the inside until the box is cut open. As mention the top is a floating panel but as the outside edge sits on the sides of the box I would like no gap at all between the lid and the side but still allow the lid to expand and contract for seasonal movement. How can I sneak up on the tightness of the joint?

The tongue that fits in the grove could be machined from the same piece as the lid or it could also be splined, one side of the spline going into the sides and the other into the lid. But how do I achieve a really tight fit?

Thanks

Brian
64680

[Paul Simmel]

Brian try as I might I just can’t get a handle on what it is you are asking.

[Martin Shupe]

I can't figure it out either.

Are you asking about the joint that holds the floating panel in the top?

Or the miter joint in the corner?

Or the "tightness" of the lid to the bottom of the box?

I am sorry I am confused, but if you can clarify the question, perhaps we can help.

[Brian Knodel]

Sorry about that fellas … I am talking about fitting the lid (floating panel) tight to the box top (red arrow) the other info in the diagram can be ignored as it is just info on cutting the box apart.

Brian
64743

[Hal Flynt]

Ok, let's see if I understand it.

I would cut the joint on the lid first. Then I would cut the joint on the side with the groove tight for the tongue and the top part oversized. (Set up your cutters and adjust until the tongue and groove fit snug, not too tight.) Next sand the top until it just slides together with the lid without a gap.

Is that your question?

I have a JoinTech setup that allows my router table to be used as a horizontal jointer that I think that I would use. I can see using paper for shims to do the same thing on a fixed fence router table. The key being to sneak up on that top to lid fit after having a snug tongue and groove.

[Lee Schierer]

I don't think you are going to have any problem with seasonal changes due to grain expansion/contraction in the vertical direction in such a small area. If the parts slip together today, you shouldn't see much difference 6 months from now either. Remember expansion is a function of total width. It is only when the width becomes big enough that the total expansion per inch becomes a factor. If you have .001" change per inch, you have only .00025 per 1'4 inch, not a number to be concerned with. Unless you plan to make the lid several inches thick, I don't think there will be a problem.

[Brian Knodel]

Thank you all for your valiant effort in deciphering my words … and thanks for your help once again.

Brian