<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px"><div id="yui_3_16_0_1_1438873234788_2375">Hi Sean,</div><div id="yui_3_16_0_1_1438873234788_2375" dir="ltr">I was thinking about making a hatch from a single piece of dished material instead of the typical dome welded to a ring etc. I have a tank head that is 7\8 thick 516-70 . I was thinking about cutting a disk from it at the apex and simply machining a flat land with o-ring groove. Is this a good or bad idea and would you be able to calculate the failure depth if I measure the depth of dish and dia.</div><div id="yui_3_16_0_1_1438873234788_2375" dir="ltr">Hank</div></div></body></html>