Full mortise door hinges are the most commonly used type of hinge.
Components of a Full Mortise Hinge
Leaf: The flat, rectangular pieces of the hinge that attach to the door and the frame. Usually these are drilled with countersunk screw holes for attachment to door and frame.
Knuckle: The cylindrical sections that protrude from each leaf, providing the pivot point.
Pin: A rod that passes through the knuckles, allowing the hinge to pivot
When installing or replacing any hinge, accurate measurement is essential. First we will review the steps to properly get these measurements.
Hinge Dimensions
Hinge sizes are based on 1) height by width (when fully open), 2) gauge (thickness), and 3) if they are round corner hinges, radius (corner measurement). Hinges may range in size from 2 to 6 inches, with the standard residential hinge measuring 3 ½ by 3 ½ inches and the standard commercial hinge measuring 4-1/2 x 4-1/2 inches.
Tools You’ll Need
Screwdriver
Tape Measure
Micrometer (optional)
Add, if round corner hinge:
Quarter
Dime
Instructions
Step 1: Remove the hinge
Using the screwdriver, remove the screws from the hinge. Use the flathead screwdriver to gently pry it off if it sticks to the wood/paint. You can also score around the perimeter of the hinge with a razor knife to free it if it is painted over.
Step 2: Measure the height
With the tape measure parallel to the side of the hinge top to bottom, measure the height and record this measurement.
Step 3: Measure the width
Open the hinge on a flat surface. Measure the full width across the center of the hinge and record the measurement.
Step 4: Standard weight or heavy weight?
The “weight” of a hinge is its thickness. A standard weight 4-1/2 x 4-1/2 inch ball bearing hinge is usually about .134 inches thick. A heavyweight 4-1/2 x 4-1/2 inch ball bearing hinge is .180 inches thick. A micrometer is required to measure these thicknesses, however, there is a short cut if the hinge you are measuring is a ball bearing hinge. A standard weight ball bearing full mortise hinge will have 2 ball bearings; a heavyweight ball bearing full mortise hinge will have 4 ball bearings.
Step 5: (If round corner hinge) Measure the radius
The hinge corner radius will either be ¼ inch or 5/8 inch. To determine this, lay the hinge flat and place a dime in one corner and a quarter in the other. Determine which fits better. If the dime fits better, you have a ¼-inch corner. If the quarter fits better, you have a 5/8-inch corner.
Choose Your New Hinges
Your measurements will help you to find the right hinge for your project. Another factor is base metal. The choices are ferrous (steel based) or non-ferrous (brass or stainless steel). Generally speaking, non-ferrous hinges are better for exterior or corrosive environment applications, however, brass-based hinges will not carry the weight that a steel or stainless steel hinge will. If the application calls for polished brass hinges on an exterior door, it may be wise to make them heavyweight hinges.