carpentry
I am holding four 44 inch long 4×4 pieces of lumber which I have sanded down to the finish I require.
I intend on using a tap & die attachment set for a corded drill to progressively drill two 2 inch holes into the corner of each piece of lumber where I will thread 1/2 inch width steel rods into, attach to the table top, and secure the legs with hardware.
Does this sound feasible? The table design is corner braced.
Looking at the picture it seems that there may be several problems going on here. In the foreground the swing out arm seems to have come completely loose from the vertical support between the legs. The C-Clamp being used to temporarily hold that part in place is not coming close to holding the hinged piece in place so it can work properly. For this side the assembly needs to be properly re-glued or screwed in place. A combination of gluing and hidden screws from the inside of the vertical support may do the trick.
For the support on the far side of the picture it looks like the top portion of the swing out arm has completely split off. Fixing this part will require replacement of the arm part or as a minimum squaring off the split top face and gluing a new piece to replace the broken away part.
One additional note is to evaluate the condition of the vertical support member between the legs. If this piece is wobbly and not secure then I would suggest that the repairs are much more involved and you may be faced with making a decision if the table is worth the effort repair at all. Overall woodworking experience and / or willingness to take on something like this may play a big role in the decision making process as well.
Evaluation would need to be made for the other end of the table to see if it has similar problems or not.
If it was me and the table had some sentimental value I would dive into the repairs. Doing repairs like this however will not do a lot to preserving any heirloom quality of the table but that has probably been lost a long time ago as noted from current condition.
I have one final comment to make. When trying to wedge up the swing up portion of the table top it is better to place the wedge out at the end of the arm as opposed to near the swing up hinge. As shown in the far side of the picture the wedge stick places an undue amount of stress on the hinge joint that could lead to further failure.
Since the new rafter section will cover any siding you may remove, layout how far the rafter section covers the siding and cut it about a 1/4 to a 1/2" lower. This will let you find the framing pretty easily, even remove a little subsiding to confirm, careful how deep you set your saw. This will show any conditions you may need to attend to. Set the bottom of the ledger at the on a chalk line set at the level you predetermined before you cut the siding. Set a ledger at the top of the rafter section as well to control rotation of the new section. This is an expansion on what Comintern suggested with his ledger and joist hanger idea, make sure the joist hangers approved for your framing condition.
Here is a little sketch to help illustrate. Doing it this way will allow a finished ceiling to go uninterrupted to the existing wall.
Best Answer
I would not weaken your legs by drilling huge two inch holes in them. Instead you could consider the leg attachment scheme as shown below. A heavy duty lag/stud bolt is screwed into the table leg. The upper inside corner of the 4x4 leg can be cut at a 45 degree angle as shown below to make it easier to drill the lag bolt into the leg.
The skirt boards that go between the legs are notched and an angled cross member is glued and screwed into the inside face of the skirt boards. The angle cut on the inner corner of the leg can also allow the cross member to get closer to the leg and be a shorter piece. A shorter cross piece will have less chance to flex. When a hex nut and washer are installed onto the threaded end of the stud an extremely strong leg attachment is created. Obviously the width of the skirt boards (top to bottom dimension) can be increased to as much as possible to increase stability of the leg attachment. In fact if the skirt board is wide enough it is possible to even use two lag bolts into the leg for even more strength.