Danny Goldstein Posted February 5, 2018 Report Share Posted February 5, 2018 I've been working on a chess/backgammon project for awhile. Each step so far has given me problems that I've worked through to fix. Before I start working on the backgammon part of the project, I have some questions regarding mortise and tenon joints. This first picture is the original plan I'm working through on Sketchup. On the short side of the backgammon board, I have 2 tenons 4 3/4" long, with a 1/2" space in between and on the ends. The long side, there are 3 tenons 6 1/2" long with a half inch space in between and on the ends. (The board is 1/2" thick, the tenon is 1/4", with 1/8" for the top and bottom of the board.) I saw a wood whisperer video on youtube (https://www.youtube.com/watch?v=BYe881bKxIA), and also a chart that indicated the tenon length should be no more than 3-5 times its width. Meaning, 1/4" width tenon, should have a length of no more than 1 1/4", with one source saying it should be no longer than 5/8" Looking for some sort of verification, the only thing I can think of, is that guide was not meant for a project similar to mine. The photos and drawing seemed to indicate things like a table being attached to a leg, or a bed frame where the attached lumber are all distinctively shorter. I'm still worried that I may be wrong, and would be better off with shorter tenons. TLDR; my question is, which is right? Can I keep the tenon measurements above, or do I have to shorten them? One thing I was looking at, is to shorten them, but not to the W x 4 rule of thumb. This is what I had in mind. All four sides of the board would have 3" tenons with 1/2" in between, and on the ends, keeping the 1/4" tenon thickness, 1/8" from top and bottom. I'm hoping this design would further strengthen the joints and help prevent the board from bowing. (Note: I did not purchase the wood for this part of the project yet.) Is this a better design than the first one above, or do I have to use shorter length tenons? Does it even matter with boards this big? (21 1/2" X 11" without the tenons) This is what the frame looks like unassembled, at the moment. As an extra note, the joints on the corner is a variation on a hidden Japanese joinery video I've seen recently on youtube. Here is a close up of the two ends side by side. And the same two boards assembled on Sketchup with x-ray view. I like the hidden corner joint, and plan on keeping it. I'm still not sure about the M & T though. Any help or advice on those would be appreciated. Quote Link to comment Share on other sites More sharing options...
wdwerker Posted February 5, 2018 Report Share Posted February 5, 2018 What kind of material is the 21 1/2 x 11 part made out of ? MDF or plywood would be fine , but if it's solid hardwood a mitered frame won't work. A solid poplar board could expand and contract about 3/8 as the temperature & humidity change with the seasons. This would blow the mitered corners out or require an extra 3/16 recess on each side to allow the movement. If you are going to veneer the backgammon board pattern then MDF would make a good substrate. Be sure to veneer the back side with a sheet of similar thickness. Quote Link to comment Share on other sites More sharing options...
Danny Goldstein Posted February 5, 2018 Author Report Share Posted February 5, 2018 (edited) I started the project with poplar, and was planning on continuing with that for as much as the project as I can, including this. But I'm not opposed to changing woods for this part of it. The overall project will be 25"L x 25"W x 8 1/2"H, with the backgammon part sitting on the inside. I'm already using MDF as a support mechanism for the lid/chess board and frame surrounding it. The main part of that board is poplar plywood with purebond poplar for the frame. Since MDF will add weight to the project, I want to avoid using more of it. Most times it will sit at home, but I do expect to take it with me to several places - at least at the beginning. I don't plan to veneer any of this. I've never worked with it and I'm not ready to start. I plan on painting the backgammon spaces. What wood would you suggest using other than MDF? If I use poplar plywood, how would that effect the M&T? Because of those, I'd rather stay away from plywoods all together. Edited February 5, 2018 by Danny Goldstein To clarify response. Quote Link to comment Share on other sites More sharing options...
wdwerker Posted February 5, 2018 Report Share Posted February 5, 2018 Poplar plywood would work just as well with no change to your tenon plan. It would let you paint your design easily. Solid wood expands in width & slightly in thickness but the length doesn't change. Plywood, particleboard and MDF are fairly balanced and behave much better. Quote Link to comment Share on other sites More sharing options...
Danny Goldstein Posted February 5, 2018 Author Report Share Posted February 5, 2018 I was always told plywood can’t be sanded down because of the layers. I thought cutting into them to make a mortise/tenon or tongue & groove, would yield the same result. The 21 1/2 x 11” is planned to be an extra half inch to start, then the excess cut to make the 1/4” tenons. (I have a feeling you already knew that.). Cutting into plywood won’t damage the wood like that? As a side question, I’m considering taking much of what’s left of this project to someone who can use a laser engraver/cutter to make the remaining parts for me to paint and assemble. (I’ve been working on this for more than 3 1/2 years.). How would the laser effect plywood? Part of the wood surface would also include an engraved design. Is that a consideration if I use plywood? Quote Link to comment Share on other sites More sharing options...
wdwerker Posted February 5, 2018 Report Share Posted February 5, 2018 Baltic Birch would be a much better choice than poplar plywood. What thickness ply are you planning on using ? Cutting tenons on Baltic Birch ply would be much stronger, regular ply would work but the tenons would be weaker. Laser engraving plywood should be fine as long as it doesn't go too deep. .02 deep should be plenty. Quote Link to comment Share on other sites More sharing options...
Danny Goldstein Posted February 5, 2018 Author Report Share Posted February 5, 2018 For the playing area of the backgammon board and the frame, 1/2" thick. The frame is 1/2" x 1 1/2" H x 22 1/2" (or 12" on the short side). For the rest of the project, widths vary. 1/2", 1", and 1 1/4". There will be 4 panels at 1 1/4" thick with a 1/4" recess on one side, 1/4" bordered on the edges and a knight design on that side. The other sides, including the 1/4" side, will have mortises, holes for dowels, and other cuts around the board, including on an edge for hardware. I still haven't figured out where I'm going to find 1 1/2" thick wood to work with. Quote Link to comment Share on other sites More sharing options...
wdwerker Posted February 5, 2018 Report Share Posted February 5, 2018 What part of the world are you located in? Quote Link to comment Share on other sites More sharing options...
Danny Goldstein Posted February 5, 2018 Author Report Share Posted February 5, 2018 Southern Florida Quote Link to comment Share on other sites More sharing options...
wdwerker Posted February 5, 2018 Report Share Posted February 5, 2018 8/4 poplar is widely available. Look for hardwood lumber, not at a home improvement center ! If they carry Baltic Birch too you've found a supplier. Quote Link to comment Share on other sites More sharing options...
Danny Goldstein Posted February 5, 2018 Author Report Share Posted February 5, 2018 What is 8/4? Quote Link to comment Share on other sites More sharing options...
Immortan D Posted February 5, 2018 Report Share Posted February 5, 2018 2 minutes ago, I B said: 10-4 Quote Link to comment Share on other sites More sharing options...
Danny Goldstein Posted February 5, 2018 Author Report Share Posted February 5, 2018 Why do they use fractions like that? Wouldn’t it be easier to say 2” instead of 8/4? Quote Link to comment Share on other sites More sharing options...
wdwerker Posted February 5, 2018 Report Share Posted February 5, 2018 8/4 is rough sawn , most yards that you would buy from should sell S2S slr - surface 2 sides & straight line rip one edge. It should be appropriately 1 3/4" thick after it's been surfaced/ planed Quote Link to comment Share on other sites More sharing options...
wdwerker Posted February 5, 2018 Report Share Posted February 5, 2018 If you don't know all this I'm wondering do you have the tools & skills to mortice , cut tenons and cut the fancy corner joints ? Jointer, tablesaw, planer , router and some very sharp chisels ? Quote Link to comment Share on other sites More sharing options...
Danny Goldstein Posted February 5, 2018 Author Report Share Posted February 5, 2018 I’ve never cut a mortise or tenon that I remember. I’m still pretty much a novice at this. Joinery in general, I have limited experience with. I have a table saw (made a sled for it last week), various chisels, but rarely use them, a router, miter saw, an electric planer somewhere that I haven’t tried yet. You are right, I don’t know much about woodworking. As a kid, I was lousy at it to the point that I would give up and my father finished some of my projects, or it got thrown out. Ecentually I gave up all together. Picked it back up about 4 years ago with minimal success. It’s become a bit of a hobby. Nothing more. Quote Link to comment Share on other sites More sharing options...
wdwerker Posted February 6, 2018 Report Share Posted February 6, 2018 I would revise the design. Use 3/4" x 1 1/2" sides and cut a 1/4" groove instead of the mortices. Cut a 1/4" tongue on the plywood. Miter and glue the corners with 2 finish nails to reinforce the miter. Fill the holes and paint it. Or practice on making the fancy mitered corner joints & mortice & tenons before you cut a single part to build the project. Quote Link to comment Share on other sites More sharing options...
Danny Goldstein Posted February 6, 2018 Author Report Share Posted February 6, 2018 3 hours ago, wdwerker said: Or practice on making the fancy mitered corner joints & mortice & tenons before you cut a single part to build the project. I appreciate the advice, and may take the one quoted here. I’m not one who backs down from a design challenge (not just with woodworking). But I do recognize good advice when I see it. I’ll see what I can do with common pine after completing the current part of the project. The frame in the last 3 pictures should be good practice. The dimensions might change to make it into a picture frame, or something else. Thank you. Quote Link to comment Share on other sites More sharing options...
wdwerker Posted February 6, 2018 Report Share Posted February 6, 2018 A splined miter would be possible to achieve with a jig you could easily build & use on your tablesaw. Definitely a bit more refined than finish nails, not to mention possibly a bit decorative. But I think a tongue and groove approach for the bottom would be easier to do and just as strong. Please let us know how it goes. Glad to answer questions as they come up. Quote Link to comment Share on other sites More sharing options...
Danny Goldstein Posted February 6, 2018 Author Report Share Posted February 6, 2018 I don’t know what a splined miter is. Also, what’s the difference between a tongue and groove, and a mortise and tenon? I thought they were the same thing. Edit: I just looked up splined miter. If I found the right thing, then it’s possible. I’d have to look into it more. What I have in mind for that is either combining it with some kind of inlay, or using contrasting wood/paint for that piece. Quote Link to comment Share on other sites More sharing options...
wdwerker Posted February 6, 2018 Report Share Posted February 6, 2018 http://www.woodworkersjournal.com/making-spline-miter-box-joints/ http://www.diynetwork.com/how-to/skills-and-know-how/carpentry-and-woodworking/how-to-cut-tongue-and-groove-joints mortice & tenon is kinda similar but it stops and starts, much easier to cut a continuous groove. Quote Link to comment Share on other sites More sharing options...
Danny Goldstein Posted February 6, 2018 Author Report Share Posted February 6, 2018 Thank you. Quote Link to comment Share on other sites More sharing options...
wtnhighlander Posted February 7, 2018 Report Share Posted February 7, 2018 @Danny Goldstein I have nothing to add to Steve's good advice, but welcome to the forum! I hope you'll find this place full of friendly help and advice, just like I did. Quote Link to comment Share on other sites More sharing options...
Danny Goldstein Posted February 7, 2018 Author Report Share Posted February 7, 2018 Thank you Quote Link to comment Share on other sites More sharing options...
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