Hi everyone,
I hope someone will be kind enough to help me with a question about installing wooden extension slides. I am building a dining table out of 1/4 sawn white oak measuring 60″ long x 42″ wide when closed (so two 30″ halves) with two 18″ leaves to extend fully to 96″. The grain on the top runs across the width of the table (IE the end grain is along the long side of the table). I have a set of wooden extension slides from Lee Valley that install to the underside of the top via screws that fit through four counterbored holes on each side of the table-top divide. However, I realized when I was about to install them that none of the holes are elongated to account for wood movement. I looked at a few plans and posts online and while I see lots of discussion about wood movement and aprons, I don’t see any discussion of wood movement and extender slides. The distance between the first and last hole on the slides is 19 1/2″ and the table-top is at 7% moisture at the moment which means that it can move up to 1/4″ (given that it is 1/4 sawn) between the first and last hole. Am I over thinking this? Do I just attach the slides and move on or do I need to account for wood movement by elongating the holes? I would normally just do it, but I feel like I am missing something since I can’t find any mention of the issue anywhere…for example see this article in FW:
https://www.finewoodworking.com/2012/03/16/extension-dining-table
Thank you everyone so much in advance for your help! The forum is always a life saver!
Best,
Mark
Replies
Hello - I would definitely italy be concerned about movement over a 19-1/2" span. What I would do is leave the holes closest to the where it expands round in order to "pin" the slides to that border. Then mill expansion slots on the other slots in order to allow expansion away from that center.
Good job thinking of that!
(By the way, if you have a Festool Domino Tool it is a great tool for making expansion slots.)
I too think it is unwise not to allow for movement in such circumstances, though it will like as not be much less than your worst case scenario - surely you are not planning on using the table in the shower? 1/4 inch is a LOT for such a distance and would require enormous changes in humidity.
Your only concern is going to be perhaps making allowance in the fitting of the leaves. Make sure they can still extend and slot into place even if you do move somewhere tropical.
I have that table. An old mission oak table that's 100 years old + and the slides are screwed tight to the table with no compensation for expansion. It seems just fine. If I was building it I would be thinking like you are. I'd elongate the holes, it can't hurt.
Just enlarge the holes by one drill size, should be plenty. Go 2 if you're worried about it and add a washer. First reply is dead on with sending the movement away from center by not relieving the innermost holes.
Most tables are built with the long grain running on the long edge. In that configuration wood movement is not in play as fas as the slides are concerned.
Thanks everyone, much appreciated
Definitely elongate the holes.
Your EMC of 7% can change a lot over the seasons. Don't forget to allow for similar moment in your leaves.
In the 80s I worked in a furniture factory that produced on the average 50 of these all maple tables every day and has been doing so for over 50 years. Since my mother still owns this set from 1985 I took pictures of the rail mount. It is screwed with pan head screws in oversize holes, you could also use washers like the back support along the underside.
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