Continuous Hinge Terminology

Hinge terms

Acceptable Burr is no more than 10% of the leaf thickness.

End Play The amount of axial movement between the leaves.

Knuckle The hollow circular part at the knuckle of a hinge through which a pin is passed. (Sometimes called loop, joint, node or curl.)

Knuckle Length The typical dimension of the knuckle measured parallel to the pin.

Leaf That portion of the hinge extending laterally from the knuckle, which generally revolves around the pin.

Leaf Width The dimension from the center of the pin to the outer edge of the leaf.

Length The length of the leaves measured parallel to the pin.

Open Width The overall dimension of the leaves measured perpendicular, or across, the pin.

Outside Diameter (OD) of the knuckle is approximately two times the material thickness plus the pin diameter.

Paint Clearance The dimension between the outer face of the knuckle and the opposing edge of the leaf cutout over the entire range of rotation. Paint clearance is a dimension and not a feature you add to a hinge. If you need a hinge that will be painted, you may need to ask for more paint clearance than is provided on our standard products. You should specify the minimum paint clearance you require.

Pin Rod running the length of the hinge. The pin holds the leaves of the hinge together.

Pitch The dimension from a point on the knuckle to the same point on an adjacent knuckle on the same leaf.

Side Play The amount of movement of the leaves perpendicular to the pin.


Swaging and open width:

  • Swaging a standard hinge will increase the open width.
  • Offsetting (away from the pin) a standard hinge will decrease the open width.
Open position Closed position
Standard assembly
Reverse assembled
One leaf half swaged
Both leaves half swaged
One leaf full swaged
Swaged to reverse
Both leaves offset

Pin Retention

[Staked Pin] Staked Pin Depressing the leaf or knuckle of one leaf to secure the pin and to prevent axial movement in the knuckle.
[Coined Pin] Coined Pin One end of the pin is deformed and when driven into the hinge, it wedges in place.
[Crimped Pin] Ends Crimped The pin is cut shorter than the hinge and centered.  Then both end knuckles of the hinge are crimped to prevent the pin from coming out.
[Bent Pin] Bent Pin The pin is usually cut longer than the hinge and bent 90 degrees.  This permits easy assembly and disassembly but no security.
[Flush Pin] Flush Pin There is no pin retention here except for the friction between the pin and the inside of the curl. This can vary greatly depending on how tight the hinges have been curled.
[Welded Pin] Welded Pin One or both ends of the pin are welded to the end curl.  This is a very secure method of pin retention.
[Spun Pin] Spun Pin Cold forming of one or both ends of the pin to a diameter greater than the inside diameter of the knuckle to prevent axial movement. This is also known as peened ends.
[Splined Pin] Splined Pin A type of pin used in some of our slip joint hinges. The splined portion of the pin is slightly larger than the inside diameter on the curl of the hinge. It is press fit and remains in the leaf for most normal applications. For applications where greater security is needed, you may want to consider welding the pin into the leaf.

Miscellaneous Terms

Back Angle The angle described by the leaves when the hinge is fully open. The back angle is usually a minimum of 270°. See the diagram below of "End View Terms".

Lock Punch

Lock Punch Temporary method of preventing leaf rotation by upsetting material from adjacent knuckles to remove end play. Lock punching is usually located on the bottom of the knuckle in a uniform pattern. This is used to keep a small cut off hinge open for barrel plating. Flexing the hinge a few times normally frees it.

Standard Cut Off

Standard Cutoff A hinge with an even number of full knuckles will have a knuckle on the left end and a notch on the right end of the lower leaf (with the knuckle facing up). Shown above.

Opposite Standard Cutoff This is opposite of the standard cutoff. The notch will be on the left and the knuckle on the right lower leaf with the knuckle facing up.

Military Specification Half Hinge Terminology

These three types are specified for Military Specification half hinges. We also use the "X", "Y" and "H" terms to help describe some application. We have an extensive list of Military Hinge numbers and their superceding part numbers.

X and Y type Half Hinges

End View Terms

Hinge end view terminology

Spring Hinges

Loaded to open

Loaded to open

The spring legs push the leaves apart
so the leaves are as far open as they
are able to be

Loaded to close

Loaded to close

The spring legs push the leaves to
meet in the closed position