All the cracks I seen from DD where screw hole cracks caused by the O ring grove not being deep enough. I never had any problems with NPT threads on any of my blocks with acrylic tops. In fact I never had a crack on any of my acrylic tops. As long as the acrylic can sit flat against the base it should be fine. And don't counter sink the screws. Use good pan head screws. I have made numerous blocks now with acrylic tops and have yet to have any problems and they do get hammered on quite a bit.
|