I love plastics. Their ubiquitous in everyday items have made life immeasurably easier. However, one place they do not excel is at hinges. Tabbed hinges on items such as fax machine trays, covers to various electronics, etc. are prone to failure from normal wear and tear. It's not that I blame the plastic for not being able to take the load bearing responsibility; the case is usually an under-engineered design that sets the plastic hinge up for failure. Fortunately, due the nature of the hinge being plastic on plastic, these hinges can be either repaired outright after breaking or reinforced to prevent the breakage in the first place. While epoxies and super glues have their uses, in this case, we need something that is going to allow the hinge to continue functioning, not to render it stationary. Thus this article provides, with the plastic utility cover on a vacuum cleaner serving as a working example, step for step instructions for fixing a broken plastic hinge using a low power drill and a metal screw.
Identify and characterize the plastic hinge that needs repaired. This may seem obvious, however, it is important to note exactly what and where the failure is on the hinge and if it can indeed be repaired. If too large a piece of the plastic is completely broken off, so much so that you cannot align the original hinge, there may be no recourse. A repairable hinge will either have the insertion pin snapped off, or maybe a missing portion that does not allow the hinge to stay in place. In our example of the vacuum cleaner cover, the enclosure keeping the hinge pin in place is missing.
Line the original hinge up as close as possible, and mark with a marker where you are going to drill a hole to allow insertion the screw to connect the hinge. In our example, we mark on the cover and the vacuum casing where we are going to insert a screw. Even though the other side of the hinge is operational, we could also reinforce that hinge with a screw to nip any future failures in the bud.
Select a screw that is A) long and thick enough to provide adequate strength to the hinge, B) short enough so that it does not to extend through any parts. This is usually an eyeball measure by holding the screw up to where it will go and seeing how it will fit. Select a drill bit that is slightly smaller than the screw; we are going to want to screw in the screw, not simply push it in. In our example, we've selected a one inch long, standard width Philips head screw.
Drill the holes into two hinge pieces using the selected drill bit and the low power drill. Drilling into plastic is as easy as drilling into wood, just take it slow. Remember you will need to drill through one piece entirely, while the other you will only need a hole deep enough to hold the screw. In our example, we drill through the cover, and slightly into the vacuum casing.
Screw the selected screw with a screwdriver to connect the two pieces together through the drilled holes and you and test the steel reinforced hinge out! In our example, the screw is threaded through the cover hole and into the vacuum casing, providing a strong new hinge that would require some serious mishap to break again.