Update: These corner-brackets didn’t work out very well. I eventually redesigned them. The redesign can be found here.
I made 7 of the corner brackets. For the eighth one I will build the corner bracket and the z-motor-bracket in one solid piece. This should make the z-motor-bracket easier to build since I won’t have to build it to fit around the corner bracket.
I used 44 mm x 44 mm blocks 1.5 inches thick for them. Since I was doing 7 of them I started by glueing two layers of 3/4 inch MDF together to create one 200 mm x 100 mm block and cut the smaller blocks out of that once it set.
Through one of the sides there is a hole 9 mm from the top through the center (22 mm from sides). On the front and back there is another hole 23 mm from the top again through the center (22 mm from sides.) These were drilled with an 8.4 mm bit all the way through the block.
The remaining holes are through the top of the block. There are four of them, one in each corner. The locations from a corner are (9, 9), (9, 35), (35, 9), (35, 35). All of these holes go all the way through the block. For 6 of the blocks I drilled them with an 8.4 mm bit.
The last block is the one labeled “Top” in the assembly directions. This has the same 4 holes on the top, but only one of them is drilled with the 8.4 mm bit. This hole should be to the right of the top hole and left of the bottom hole. The other three holes were drilled with a 5.4 m bit.
These blocks are 6 mm taller than they are supposed to be. As a result, the z-posts will protrude 36 mm below the corner brackets instead of the 42mm called for in the assembly instructions.