A: Hinges come in a bewildering array of types, even among European styles found on most modern cabinets, including yours. These are also called 35-millimeter hinges, because one end has a cup that fits into a circular hole that’s usually 35 millimeters in diameter cut into the back of the door. The other end of the hinge slides into or is attached to a mounting plate screwed to the cabinet box — or, in the case of bifold doors, to the door hinged directly to the cabinet. Between the cup and the attachment plate, more screws allow adjustments to the door’s position.
That’s where the complications begin. Lots of different companies make Euro-style hinges, and the number of adjustment screws and their roles isn’t the same from brand to brand. Bifold hinges can be especially puzzling. If the company from which you bought the cabinets comes to your house again to fix the problem, ask the repair person to explain how the hinges adjust, and take notes.
If you need to figure this out on your own, look carefully at the hinge to see whether the manufacturer’s name is on it — perhaps on the cup. Or, because you bought the cabinets relatively recently, call the company you bought them from and ask. You can then search online by typing in the manufacturer’s name, “bifold hinge,” and terms such as “installation guide” or “adjustment.” This may lead you to a drawing that shows what each screw is supposed to do or a YouTube video that walks you through the adjustment process. Or you can just turn each screw in and out while watching to see the effect on the doors. Use a basic screwdriver rather than a power drill or driver, because it’s easier to control. A few turns of a screw should be all you need to see what that screw does.
Because only one hinge is misbehaving, perhaps the two good hinges will help you figure out why the bottom one pops loose. Look at all three carefully and try to spot any differences. Are they all securely attached, both at the attachment plates and at the cup holes? Some cabinet doors are made of materials that don’t grip well to screws, so if one or more of the attachments wobble, you may need to remove the screws, insert plastic dowel inserts and then reattach the screws. Rockler sells these as part of its $2.49 Hinge Dowel Repair Kit.
Also compare the attachment plates on the three hinges. The picture you sent shows that on your hardware, this plate has three screws. The top and bottom ones clearly allow you to adjust the height of the doors; that’s why the recesses for the screw heads are oval rather than round. The middle screw looks as though it should be holding the angled part of the hinge in place, but the screw head seems to be slipping right through, causing the door to pop loose. Do the two other hinges have a larger screw in that location, or is the square piece of metal behind the middle screw acting as a washer to keep the screw head engaged? Or perhaps the hinge is warped so the screw doesn’t engage where it should. Do the parts fit together more loosely on the bottom hinge than they do on the other hinges?
If this process hasn’t revealed the problem, remove the bad hinge and move the middle hinge to that location. The weight of the door might dictate using three hinges, but two should be sufficient for a quick test — as long as you don’t slam the doors around. If the door still pops loose, perhaps the cup hole or screws holding the attachment plate are in the wrong place. Compare measurements with the other hinge locations. If the attachment plate needs to be closer or farther from the edge of the door, plug the existing screw holes with short pieces of wooden toothpicks and wood glue, then redrill in the right location and reattach the plate. If the cup hole is off, the cabinet company should give you a new door.
If the door functions correctly with only two hinges, the hinge you removed is probably faulty. Ask the cabinet company or manufacturer to replace it (check the warranty). If they won’t, you can buy one if you know the manufacturer. If not, you might need to replace all three hinges to ensure they work well together. Make sure the cup size matches the hole in your door.
Once you have working hinges, you’ll need to adjust the doors. The outside corners of the doors should just about touch, with only a thin, even gap between them. Close the doors, and, facing the corner, stare at the gap. If it’s uneven, find the screw for diagonal adjustment — it’s probably on the hinge close to where the doors meet. Tighten or loosen that screw as needed. Then, if the outside corners of the doors don’t almost meet, move the door that’s not attached to the cabinet in or out or sideways by adjusting other screws, which are probably close to the attachment plate.