Design Failure

My plan was to use 1/2" ID 5/8" OD bearings with little square blocks 1" square to hold then in place inside the axis housings.  The 5/8" OD bearings are actually. 5/8" OD.  To make the bearings fit requires a .704" hole.  This gives .296"/2 on either side of the bearing block into which I need to epoxy a helical thread insert.  I bored 1/4" diameter holes in each side because I thought I ordered 6-32 to 1/4"-20 inserts which were. 138" long.  They are fine inserts.  Notice where made:

They are actually for an 8-32 through hole.  This is not surprising.  I could use 8-32 screws in 1/4"-20 holes, but those inserts will not be short enough to fit in .145" deep holes.  I think the solution is to:

1. Measure each component as it arrives (bearings OD, helical thread OD).

2. Drill much smaller holes to accommodate these Down Under inserts.

Drilling the existing 1/4" holes down to .145" will require a mill that operates in a Lobashevsky space.  I cannot afford that.

Fortunately,  I only milled the 1/4" holes in one besting block.

To hold the block and grab the outer ring of the bearing will require 3/16" screws.  They are fortunately available