[Dave at Pelican Parts]

Green71, the triple-square holes in the bolt heads should not be shallow; they should be the same depth as regular Allen head bolts. I'm betting that they were partly filled up with crud that had been sucked into the fan over the years.

Chances are that Allen-head bolts would have been filled up similarly.

The solution is no further away than your favorite can of carb cleaner or penetrating oil. Use the little hose to spray this stuff into the bolt-head. Then put the correct tool into the recess in the bolt head, and give it a firm tap with a mallet to make sure it's seated. It should come out pretty reasonably.

The triple-square bolts actually have more surface area to distribute the tightening/loosening torque across, so they should be a bit less likely to strip if you get the tool fully engaged.

--DD