Table Stretcbers and Allowing for Wood Movement
Hello,
I would appreciate any advice and/or comments on how to best allow for wood movement in a 5″ table stretcher.
The table stretcher is planned to be mortised in the centre of the two (2) wood slab legs tight up against the bottom of the table top. I intend on mortising the stretchers fully (no tenon’s) in the legs by 1/4″ and securing them with two (2) – 3/8″ bed bolts through each of the table slab legs. The 1/4 mortise is a positioning mortise only but should I make them a bit larger to allow for the 5″ flat sawn stretchers to move with expansion? I would like to avoid having the stretcher expand and push up the table top seasonally.
The little information I have been able to find on this issue has indicated you don’t really have to concern yourself with wood movement in aprons or stretchers up to 5″ wide. But, I have experienced wood expansion (however slight) in the rails of the cabinet doors of a country hutch I recent built. So if a 2″ rail has moved I’m pretty certain a 5″ stretcher will.
Any thoughts and comments/guidance would be much appreciated.
Thank you
Replies
First, I would not expect a large amount of movement from a 5" wide board. However, you can use one of the on line tables that will tell you the amount to expect depending on the species and expected changes in temperature and humidity. I expect that you will find the movement to be negligible. However, if you want to allow for a small amount, make the mortise longer than 5" (maybe 1/8") and then place your upper bolt to constrain the movement at the top. Then make a vertically elongated hole for the bottom bolt to allow it to move with the wood. This way the movement will not adversely effect the table top, but the bottom edge will be free to move up and down. An easier way might be to make the bottom bolt hole larger by the expected amount of movement. This will allow the bolt to move within the oversize.
Making the mortise a bit longer than the stretcher width and elongating/enlarging the lower bolt hole will take care of it. My tendency would be to hide the expansion allowance by cutting the tenon a bit shorter (say 4.5") and having the mortise be 4&5/8". I do this kind of thing often with the haunch when making a haunched mortise and tenon joint with a wide board.
Thank you both bildyo and JHarveyB. I will follow your collective advice and make room in the mortise, firmly secure the top bed bolt and elongate the lower bolt hole to allow for wood movement.
Much appreciated
Or, you could just use glue.
You could make the tenon shorter IOW, put a small shoulder in the stretcher that covers the mortise. Slightly larger holes will allow bolts to move a little.
This forum post is now archived. Commenting has been disabled