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The easiest way is to make a template to locate the screw holes for the hinges. A template is a guide to help you position the hinges. It can be as simple as a small block of wood that is placed on the inner hinge side of each door. Use this block to locate the "outside" hinge screw or just the outside edge of the hinge... outside meaning towards the upper or lower edge of the door. Now you will be able to install all the door hinges in precisely the same location for all doors.
Lower cabinets normally have the same door height. However, upper cabinets have varying door sizes. If you have smaller doors next to larger doors (such as with the mini-cabinet over a range hood or refrigerator) locate the upper hinges and the tops of the doors so that they are aligned horizontally. It gives a clean visual appearance.
This is a good reason not to locate the hinges too far down the side of the door… a few inches from top and bottom is sufficient. If the doors are more than 30" long, you should install a third, centered hinge. Don't even bother to install the third hinge until the door is hung… it just gets in the way!
You can use a template to locate the doors on the cabinets, too. Mount one door as a test. Be sure that the door is vertically centered over the cabinet opening and mark the location of the hinges. Test fit the door and if it is OK make a template to locate just the top hinge. Since the hinges are already mounted on the doors, the bottom hinges will automatically match up without measuring.
The only possible drawback to this is if the cabinets do not align perfectly. So you will have to make judgements as you proceed as to whether or not you want to "tweak" the door locations to match irregularities in the cabinets. The "aesthetic" rules in renovation!!
One "trick" is to only install one hinge screw in each hinge for the cabinet mounting. This way, if you want to make a slight change in the location, you will have a second chance by using the second hole. If all your errors are under the body of the hinge, no one will be the wiser (Hey, heh, heh!).
It depends on the type of hinge that holds your doors. If they are standard "self-closing" cabinet hinges with no adjusting screws, they are probably damaged and need replacement. Heavy doors can distort light-weight hinges. And just plain wear-and-tear can cause the metal spring that operates them to break. Telltale evidence of this is when the hinge makes a sudden "cracking" sound and little pieces of plastic or metal shower to the floor. Even though the doors may still open and close, there is no force keeping them shut so they stay partially open or even resist complete closing. Light weight doors can still self-close with one functioning self-closing hinge... heavy doors rarely do.
There is a second type of common cabinet hinge... the so-called "Euro" hinge. Euro hinges are complicated-looking mechanical hinges that defy understanding... at least at first glance! However, if you examine them with patience, you can figure out how they function. Unlike standard cabinet hinges, Euro hinges can be adjusted to both align the doors and to close completely (assuming they are not broken, of course).
A Euro hinge may have two or even three methods of adjustment, depending on the manufacturer. You will notice that there are a number of visible screws on the body of the hinge. (You might have to pop off a decorative plastic nameplate to get to some of the screws.) Each screw performs a function. Some just hold the hinge together, some are for adjustment only and others perform both functions at the same time. Tightening or loosening the screws is required to adjust the hinge. If the screw offers you the option of using a Phillips or slotted screwdriver, use the slotted... it gives more turning power with less slippage!
Some of the possible functions of the screws are:
1) to hold the hinge to the door or cabinet frame. These may be visible OR may be hidden under the hinge mechanism. Some Euro hinges have two parts... the actual hinge and a "base" plate that is mounted onto the cabinet.
2) to adjust the cabinet doors up or down. These screws may also hold the hinge to the cabinet OR the hinge to the "base" plate (as described in (1) above). Obviously, if a door needs vertical adjustment, ALL hinges holding the door must be adjusted together to move the doors.
3) to adjust the cabinet doors left or right (towards or away from each other). This is the hallmark adjustment of Euro hinges, allowing you to align the doors even if the face of the cabinet is not square. Adjusting one hinge will tip the door... adjusting both will move the doors towards or away from each other. If the door has more than two hinges, the adjustment becomes more complicated. One solution is to temporarily disconnect the center hinge(s) and make adjustments with the top and bottom only. Once the door is aligned, reconnect the center hinge(s) so that it does not change the alignment. Can be tricky but definitely doable!
4) to remove the hinge "body" from brackets attached to the cabinet. This adjustment is also used to move the doors closer or further from the cabinets when the doors are closed.
If a visual inspection doesn't give you a clue as to the screw's function on your hinges, make careful changes in their adjustments and see what happens. Right... good old trial and error! Just be sure to work on the "bottom" hinge only when experimenting. You'll have less chance of a door falling into your lap if you make a mistake!