[Joe Johnson]

Thanks for pointing this problem out.

This is one of the trickiest parts to make.

The part is hard and the wall that is left is very thin*. The machinist needs to take very small cuts with a carbide boring bar or (my perference) you need to find a good wire EDM source.

Joe J.

*in fact it was so thin, there is no engineer I trust that says it should work, I myself doubted it would hold up, but thankfully, testing is the ultimate authority.