Wood – How to fasten boards flush to the face of square posts

Dowels are probably your best bet for this fix because the tool cost is much lower for the case that you need to purchase tools to do this repair. The cost of a doweling jig is much lower than a biscuit cutter. Drilling the dowel holes is easily accomplished with an electric drill.

If you end up with just a one inch wide repair strip added in then I would just drill the dowel holes right through the strip and into the original material on each side. Do check your table top pieces for overall flatness after you separate the two sides from the split. Warped lumber often develops a curvature that spans a greater distance than just one inch. You'll need to take this into account when you decide to start trimming away the split edges.

With properly jointed surfaces on the two trimmed edges and the hardwood accent piece the dowels and glue should be plenty strong to hold things together.

You may want to cut the accent piece just a small bit longer than the amount needed and then trim and sand it to the existing round table edges after the gluing is done. This will give you the greatest opportunity blend the edge of the table to the nicest fit and look.

I see some challenge in clamping the round table to get good tight glue joints. You may need to fabricate some jigs to help provide a place to engage your clamps across the width of the table. The sketch below shows one idea of how to do this. Some flat boards about 4 -> 5 inches wide can have some blocks glued and screwed on the ends that will provide a place to engage the clamps.

I have shown the blocks somewhat offset from where they would actually be attached to the boards so that you can see the nature of how they would fit to the contour of the table edge. Long bar clamps or pipe clamps would be spanned across the table top at the overhang of these boards as shown in the next picture.

Considering that you have a relatively high sideboard/headboard and footboard arrangement, that can be used to help strengthen the headers around the perimeter. The strength of a piece of 3/4" plywood, 21 plus inches tall on the sides alone with a small ledger to support the joists and bed slats is sufficient if all is glued and screwed together and has a sufficient bearing surface, 1" is ample.

Since it is for sleeping, typically at most for two people, and if you have kids too, the bed would need to hold say only the weight of 4 to 6 people, then add a little more to cover murphy's law so the weight of 2 adults and 4 kids may run about 700 lbs., let's take that to 1000 lbs., kids jump up and down.

The bed you have at nearly a 7 ft average on both sides will yield 49 sq ft, multiply that by 40 lbs/sq ft and it will carry 1960 lbs. a little overkill but ok. So the live load using the AWC calculator at 7 lbs dead load and 30 lbs live load at 16 inch centers you can use 2X6's and still carry a 10+ span with SPF or 8+ with D Fir, plenty strong.... The same calculator gives a recommendation for the bearing ends of .30 or so of an inch, Don't be fooled on what an inch of bearing can do. I would expect if you mortise the ends in and secure it with a screws (gauge your screw length properly for end grain) It will do all you expect.

The matter at hand is the headers at either end, I had supposed the side boards etc., were to be fixed permanently to keep the occupants safe, therefore I was going to use that as part of the structure too to keep the bulk of everything down. If they are to be hinged or drop down then the header will need to work on its own, I would suggest using a 2X8 for the perimeter, mortise and tenoned for shear strength and use a captured nut with bolt to draw the joints together. That with the face of the 2X8 against the faces of the legs will give a lot of lateral resistance. For your own investigation, and practice on making this critical connection, make a sample joint and put it to the test. I have used this type of connector to hold a 7 ft wide 4 ft tall gate out of 2 inch thick solid mahogany using standard bolts and site made washers to fit the slot for the nut- Four 1/2 inch bolts were used for this, still hanging after eight years outside Just as a mention, and you may know this already, the AWC calculator is for home building, quite the different animal than furniture making.

Reread your comment and missed a point, if the mortices were not all the way through and the bottom of the mortice was 2 inches plus above the bottom of the header with no knots or curly grain, it will not weaken the header enough to cause concern. Give a look at some of the beds at places like Ikea or Crate and Barrel, or something like that....