Table top fasteners and "cross grain" expansion

[Maurice Arney]

Hi people... Could someone give me the "nutshell version" of this concept and when I need to use them and when it isn't necessary? I have built small tables in the past and used corner braces from the local hardware store to attach the top. I just finished a 48" x 24" center island with a cherry top and wonder if it is a bad idea to do the same. For the top, I glued up seven pieces of 5/4x6 cherry to make a top 60"x38" which gives an overhang on the back and one side for a breakfast bar. I am ready to fasten the top but will need to order expansion clips if it is unadvisable to fix it permanently with corner brackets. Does it depend on which way the grain is running?


Thanks!

[Sean Hughto]

The nutshell version: you need to account for movement; wood does not move perceptiibly in length (with the grain), but moves a good deal with humidity in width (across the grain); a 38 inch wide top will move perhaps half in inch from season to season; you screww it down all around with corner brackets. the top will likely split; you can tie down one side or the middle, but eh rest needs to be able to breathe; if there is an apron, buttons running in grooves are good choice, figure 8 fstners are another alternative, etc.

[Maurice Arney]

The nutshell version: you need to account for movement; wood does not move perceptiibly in length (with the grain), but moves a good deal with humidity in width (across the grain); a 38 inch wide top will move perhaps half in inch from season to season; you screww it down all around with corner brackets. the top will likely split; you can tie down one side or the middle, but eh rest needs to be able to breathe; if there is an apron, buttons running in grooves are good choice, figure 8 fstners are another alternative, etc.

Thanks... That makes more sense now. What is confusing me I think was looking at the "figure eight" fasteners. I can't see how they would allow movement across the grain if they are screwed to both the counter top and the carcass. So if I use the ones that fit into a kerf underneath, then that kerf must be deep enough to allow movement in an out (as well as side-to-side)?

[glenn bradley]

You leave room for them to pivot.

[Sean Hughto]

So if I use the ones that fit into a kerf underneath, then that kerf must be deep enough to allow movement in an out (as well as side-to-side)? Well, just remember how the top will move, right - some will only move along the kerf/slot, but ones on other sides will only move in and out of the slot.

[Maurice Arney]

You leave room for them to pivot.

Ah... I see how it works now :)

[Maurice Arney]

Well, just remember how the top will move, right - some will only move along the kerf/slot, but ones on other sides will only move in and out of the slot.

I understand. Thanks for clearing this up for me.