Sawdust build-up can create heat and friction when you use a hole saw. One solution is to drill a smaller hole inside the area to be cut out that will allow the sawdust to escape. Size the relief hole according to the size of the larger hole. If, for example, you are cutting a 3-in. hole, drill a 1-in. relief hole. Don't drill the hole too close to the center, which you need for the saw's pilot bit.
Bulkheads usually come in kits. Lay out the pieces first and follow the directions step by step, and it should only take you four hours or so build. Before you secure all the bolts, make sure the doors close and latch properly. Then seal the base with mortar. Slope the edges to keep your bulkhead watertight and your basement dry.