Starting Point

Here is the block, in its un-molested state.

Taped

As this block will most likely not see a parts cleaner again, I wanted to be sure that none of the metal bits fell down into the internals, potentially causing a catastrophic situation at a later date.

Blocked

The drill press and block need to be on as even a plane as possible, to ensure that the holes are vertical. If they are not vertical, it will be very difficult to thread the bolts back in!

Tap Set

This is the drill and tap set I purchased from Home Depot. Rather nice that they come together, as that ensures that there is no guesswork about what size drill to use.

Drilling Holes

Though the flash made it look as if it's not running, the drill is turning, and removing metal in preparation of tapping...

Filings

A nice pile of metal filings ends up stacked around the hole. But rest assured, there are filings inside the hole as well.

Checking Once

As with the drill, the tap must be as vertical as possible. Getting the tap off-plum will ensure a canted bolt, which does no good for clamping pressure, nor the longevity of the bolt.

Checking Twice

I checked the tap, again, at 90 degrees to ensure it was perpendicular to the block from all angles. I only eye-balled it, but that's close enough for this application.

Tapping

Once alignment of the tap has been set, and the tap started, the tap holder is put in place, and the real work begins. I used a cutting lubricant (Tap Magic, in this case) to ensure no binding, and only cut a couple of threads, backed off a half turn, then cut a couple more.

Chip Removal

With the removal of the two studs, there are five blind holes in the block to transmission interface. I found that magnetizing an allen wrench, with rare earth magnets in a plastic bag, did an admirable job of removing chips from the holes.

Proof

Here is proof positive that this method was working.

Ground Tap

Once all of the holes were tapped, I ground off part of the end of the tap bit. This allowed me to cut an entire thread more than before. It may not sound like much, but this can be significant!

Voila!

Finished holes, in 5/16"-18... D'oh!