Making Wooden Dining Table Extension Slides
- Anyone know of a stable species that has the bridging capacity and strength?
I've made a few sets of these over the years and found that any reasonably stable wood will work. I have bought a few sets, and I believe they were beech - not necessarily the most stable wood. And like you, I found the slides to be poorly made. I think that a certain amount of slop is inherent in wood slides, as having them bind would be more objectionable than having them sag. The sets I bought didn't have any noticeable camber in them, probably due to the relatively crude manufacturing involved. It's possible that you could work out the proper curves and CNC them, but then it would be hard to mount the slides to the bottom of the table.
I have had better success with metal versions of this slide - Watertown Slide Company makes the ones I used, and they worked reasonably well. They may have moved their production offshore and suffered the usual decline in quality, or they may be dead already.
There are better ways to make tables open, but if you just need one or two, I would make them in house - at least you'll get good wood. I'd recommend hard maple.
From the original questioner:
Thanks. Metro does approximately 15% in custom millwork business for established customers. The customer in question has an aversion to ballbearing slides and euro hinges... No idea why? I have in-house supply of maple/walnut/cherry/oak. I'll try the maple first and "trial and error" this thing out with the CNC router.
From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Most woods are quite similar in their stability in-use. Oaks are on the high side of movement and many lower density woods show less movement. The secret for initial movement is to get the pieces dried correctly. Once dried to 7.5% MC or 7.0% MC, they will not move during manufacture, initial use or year after year.
As strength and smoothness and the lack of twisting when the MC does change are keys, beech is the wood of choice. It machines well and is uniform. It sounds like you may have been getting items with poor initial moisture control.
Note that the width of the slides is not as important as the height, with respect to strength. (Consider a 2x4... step on the flat side and it bends a lot; step on the edge and it is much stiffer and stronger.)
Wax is a lubricant and also seals the wood from moisture. It is applied after finishing, as if applied before, no finish will stick on the wood. Some pieces have used only wax based finishes.
Overall, my suggestion is to try a new (and better) supplier, rather than learn a new technique and have some rejects of your own.
From the original questioner:
I don't really have anything to add from my experience, but the finger joints sound like a bad idea in this application.
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