The easiest way of getting all the angles and lengths right is to draw a full size plan of the end frame on a large piece of paper. Pin it to the floor and mark off your timber against it. This way you will not have to struggle with calculating angles and triangles. Include the marker lines so that you can easily see where to mark your wood when it is laid on the drawing. The bottom of A has a tennon that fits into a recess cut into the end of C.
The socket cut for the tennon on the bottom of A in C should be a good fit side to side and the external face should be accurately cut. However extend the socket quarter of an inch further in towards the central leg to make it easier to assemble and dis-assemble. The top of A is not a tennon but wedges up against the end of the lathebed and the central leg. The force required to hold the legs into this position comes from the following construction.
1. Cut the leg B half an inch (12mm) shorter than on your plan.
2. Drill a 10mm hole centrally into the bottom of B.
3. Slightly widen the very start of the hole to 12mm.
4. Screw a 110mm (4.5") length of 12mm threaded rod into the bottom of the leg until about 50mm is in the wood.
5. Drill a 20mm hole 10mm deep centrally in the bottom of C and then continue the hole with a 12 mm drill right through. The 20mm hole will form a recess for the nut that goes on the end of the rod inserted in B and passed through C.
6. Drill two 20mm recesses and 12mm holes through the lathebeds D and the top of the legs B
Now when the beds (D) are bolted tight to the legs (B), angles (A) are inserted into the base (C), held in place while the nut on the rod is tightened pulling the base (C) hard up into a slight bow caused by B being slightly shorter than drawn. The force of this will pin the angles (A) tightly in place between the base and the bed. It is actually easier to assemble the lathe upside down. Bolt both B s to the upturned lathebeds (D) and then put a C in place with a nut two turns onto the rod. Slip the two angles (A) into place, gravity will hold them once they are in and resting on the bed. Tighten the nut and repeat the other end. now turn the lathe over. You should find that the whole thing holds together quite rigidly. The wear feet serve several purposes apart from preventing wear on the base. The lathe will stand better on uneven ground and is more stable due to the weight being transferred to the ground via the extremities of the base, rather like standing with your feet apart.
Hint: to screw threaded rod into wood you can do the following; take two nuts and thread them onto the piece of rod. If you then tighten one against the other they will lock on the rod. Now you can wind the 12mm rod into a 10mm hole so that it forms its own thread in the timber. Remove the nuts by reversing the locking procedure. I did this four years ago and the rods have shown no sign of pulling out.
Hint: Use 10mm threaded rod and drill 20mm recess with 12mm holes to attach the bed to the legs to make it easier to line up and slip the bolts in. Use stout washers wherever nuts would come into contact with wood so that the wood does not get chewed up.