How to attach arm rest while allowing seasonal movement
Hello,
I am building a table that will be be used to dine or play games when three floating leaves are removed. The table is 76″ long, 48″ wide made out of 3/4″ thick quarter sawn iroko and some plywood. As per the attached PDF, there is a 6″ wide arm rest below the leaves that looks like a picture frame. The mitered corners are glued and fastened to each other from below. The frame mates to the rest of the arm rest assembly (4 in total, one per side, separate) that includes a playing surface wall and a plywood bottom attached to an apron.
I see the frame as a table top with a large inside hole, that needs to move a bit (not the entire arm rest assembly), while keeping the joints between the bottom inside corners of the frame and the 2-3/8″ high playing surface walls always tight and flush (ideally with glue and screws, item #2).
There is limited access to the arm rest cavity and envision attaching z clips while the frame is on its own upside down on a flat surface in either of two ways. I would then drop all of that over the table and fasten the rest from below.
Both approaches rely on additional blocks of wood (item #1) for the z clips next to the aprons, fastened to the aprons from the top through the round holes for additional lateral stability.
The question is how to approach the inside portions of the frame. One option (item #3) would rely on fasteners instead of clips, from below through elongated holes that allow front to back and side to side movement (hand tight to control up and down movement). I have not yet settled on the size of those holes, or if 3/4″ thick plywood will accommodate counter bores without large protruding washers.
The other option would rely on additional z clips and blocks of wood (shorter, item #4). In either case, adjustments or repairs to this assembly would be made by removing all the fasteners accessible from below. I envision placing the z clips 6″ apart.
I would appreciate your feedback as well as alternatives to the above.
Thanks
Marco
Replies
I've never heard of or seen a table with arm rests. It's very hard to understand what the plan is depicting. Do you have photos of a finish one from several different angles?
Thanks for your feedback.
This table I found on Etsy just now is not what I am building but it's close enough - https://www.etsy.com/ca/listing/1027135035/custom-gaming-table-dd-pathfinder. It does not show pockets for drinks, cards, dice, etc. but this one does - https://makezine.com/article/home/fun-games/how-to-build-a-high-end-gaming-table-for-as-little-as-150/.
One would place their arms on the outside arm rest / frame as they play a game in the center. What my clients call a vault, and I referred to as a playing surface. The inside wall at 90 degrees to my surface is 2-3/8" high.
I have attached two PDFs of what I am building, one for either end of the project, both incomplete. It's work in progress so you need to imagine a complete plywood based playing surface, and inside walls all around (and pockets routed into each arm rest / frame). I show a complete inside wall at one end, an incomplete one along the long length, and nothing on the other sides. I have not cut the actual pieces to final length because it's been a challenge to find enough Iroko to work with and I cannot afford to make a mistake.
So my challenge is to keep this arm rest / frame in place, joints tight, and still allow some seasonal movement, so the corners (or some other portion of the frame) don't stress themselves apart. I imagine mostly side to side movement, but suppose that one or more sides might need to move a bit at around the same time each in their own way, so I want to allow that but keep joints tight, especially where the bottom of the arm rest / frame meets the top of an inside wall. Both are made of solid Iroko. I am not concerned with movement within an inside wall since it's grain is aligned in the same direction as arm rest / frame above it. The leaves will sit on top (not inset like the links) of the entire assembly and make the table 1/2" longer and wider than what's underneath it.
Thanks
Marco
I would make a suggestion that if you post drawings with a lot of unclear information - that you use typical drawing descriptions such as plan, elevation(s), section - and use standard combination *to include* those as well. It is very difficult to make sense of this drawing.
I don't get it.
Stop overthinking it.
Your design is ok.
The only point of concern is the use of plywood for the arm rest base - I would either use ply for the arm rest with veneer and a solid edge band (best) or solid wood for the base of the arm rest - in both cases your concerns about wood movement go away. You just have to use the same material for the top and bottom of the arm rest box section. Clips, toggles and such are surplus to requirements.
The best way to look at this is a rectangular box section and frankly the best way to build those is from quality engineered materials.
What rob_ss said.
I would only amplify his last sentence. The arm rest appears to be 5 or 6 inches wide, resulting in relatively long miter joints at the corners. If you use solid lumber, seasonal movement will try to alternately open and close the inner and outer ends of those miters.
I can imagine wanting the arm rests to withstand more abuse than commercial veneered ply will provide (not to mention the hassle of edge banding all of the openings). So if you want to stay with solid lumber, you might consider an alternative to miters at the corners. Perhaps a decorative open miter with a floating spline, or a Greene and Greene like breadboard treatment, or something like Erika Torres did for a similar convertible game table: https://www.instagram.com/madera.by.erika/ (one of her pinned projects at the top).
Hi,
Big thanks for your responses and apologize for any confusion. Should not have added a view of the box section inside the middle of the plan view, and not sure what happened to PDFs of photos of work in progress including links to commercially available gaming tables that initially inspired the project. Wear and tear was a consideration; wanted something special and eventually settled on Iroko. All components were built and some glued months ago but not completely assembled (i.e top to bottom of each box section).
Apologies for any repetition, but the entire table except for box section bottoms and playing surface is made out of solid 3/4" thick quarter sawn Iroko. Each section consists of a 6" wide arm rest top, a bottom, and two sides (3" apron, 2-3/8" inside wall). The bottom is made out of 3/4" thick baltic birch. The outside edge is fastened to an apron and a lip on the other side supports a separate playing surface (also baltic birch, with additional supports under it).
Looks like it would have been best to follow either of the suggestions offered by rob_ss, WITHOUT glueing and screwing the miters. Box sections made out of engineered material would have reduced movement, so much so that glued and screwed miters would not have been an issue (or nothing elasticity in the glue or wood could not handle, probably without interfering screws). Sections made entirely out of solid wood could move at the same rate.
I introduced a different rate by using plywood bottoms but intended the bottoms to move with their corresponding apron and inside wall. The arm rest top would float above. Either way, I am not clear how else I could attach the arm rest top to the apron and inside wall since there is no access from below, limited access within a box section cavity (2-3/8” height), before an inside wall is attached. So far decided against glue, dowels and tenons, leaving me AFAIK with clips or elongated holes.
Seen but not used splines before, and found an interesting discussion on the FWW discussion forum titled “Spline Joint Question” dating back to 2006. At one point PJohn notes that "In practice, a reinforced joint will withstand considerably more stress than a simple butt joint. Interior joints are likely to see less moisture-induced stress than exterior. Quartersawn lumber moves half as much. Is he safe? Maybe.”. In the same discussion Pondfish notes that splines will not help with movement.
I take it that even if my miters end up working a long time, the risk will remain so it’s prudent to avoid it altogether. I like the idea of a floating spline but don’t see how it could maintain tight miters. Or maybe that’s the point, there will gaps. But then how do I prevent the arm rest top (aka picture frame) from moving around, especially as separate pieces? Am I back to clips, aprons and inside walls to maintain control while splines close as much of a miter gap as possible? Or crazy as it sounds, leave the mitres glued and screwed until an issue arises? Probably don’t mean the last one but I will ask anyways.
Thanks
Hi - I submitted two comments since my original post. The last one after JEarch. Please accepts my thanks if you get this one, otherwise I will wait to see what happened to those comments.
I will echo a previous poster, don't overthink it. You are using quarter-sawn lumber. That puts most wood movement in the 3/4" thickness direction. So an individual board will get slightly thicker or thinner with seasons not wider or narrower. So your miters will be safe. You can do what ever you want to attach the arm rest assembly to the table.