Drilling perfect mounting holes used to be tough and once served to "build character" in a modeler. But now, several companies sell tools that make this job so simple, fast, and troublefree that some of us have to find other ways to become "characters." A photo shows the Great Planes Dead Center engine-mount-hole locator in use, and several other manufacturers make almost identical tools.

To properly use this tool, you need to make a mount fixture or possess a drill-press vise. The fixture is easy to make. Join two pieces of 1/2 plywood (approximately 6 inches square) with epoxy and screws so that they are perpendicular. You will use this fixture throughout your entire modeling career, so make sure it is correct and well braced. Screw the engine mount to this fixture, making sure that it is level and square.

Position the engine, hold it in place, and use the tool to drill one small, shallow mark in a mounting beam. Mark only one hole for now. Remove the engine and drill the hole. What size hole? You should use the largest hardened socket-head machine bolt that will fit inside the engine's mounting holes. The screws that came with your engine mount are okay, but hardened steel bolts are stronger and easier to install. Most .40 engines use 4-40 or 6-32 bolt sizes.

After you have drilled the hole, tap matching threads into it. Fiberglass is softer than metal, so use a drill that is one size smaller than what is printed on the tap. Use a No. 37 drill for 6-32 bolts and a No. 44 drill for 4-40 bolt holes. It is best to use a drill press and the fixture you made (or drill-press vise) here. You can buy a good drill press for less than $40, and they are good investments; you will use one for many years in your modeling.

Do not use oil to lubricate while tapping the threads; the fiberglass contains enough carbon to lubricate the tap. Some oils can weaken the mount material, causing the threads to break or "strip out."

Using the hole you drilled and tapped, remount the engine, check to make sure that everything is still positioned correctly, and then mark the remaining three holes. It is best to drill and tap one hole at a time, remount, and then mark the next hole. This is not essential, but it can prevent cumulative errors because each hole may be drilled slightly off center.