The first aluminum build plates had to fit around the gimcrackery atop my tweaked ABP: two solderless grounding lugs and a lump of Wire Glue. The new HBP setup put the grounding lug below the fixed plate and did away with the lump, so the removable plate could have five holes and a wiper cutout without any fancy trimming.
I’d squared up three plates and machined only two for the ABP, so I had one plate that just needed drilling. Rather than machining two new plates, I filled the cutouts on the old plates with JB Industro Weld epoxy, flycut the excess, and drilled new holes.
This was straightforward manual CNC: get the plate square on the table, touch off the plate edges, and then drill the holes in two steps.
If those thin epoxy webs break off the outside of the holes, it’s not the end of the world: the plates won’t go anywhere because they’re indexed by the holes on the other side.
Memo to Self: Next time, make a fixture to hold the plates relative to a starting hole and eliminate all the tedious alignment steps.