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Standard Measurement
For professionally installed mortise and tenon joint Hinges, the standard and ideal exposure method is:
1/8 inch (approximately 3 millimeters).
This measurement is the total gap between two leaves. When measuring across two closed doors with a ruler, you should see a consistent 1/8 inch space from top to bottom for the hinge.
Why Is This Specific Measurement Important
1. Preventing jamming: This gap is absolutely necessary for allowing the door to swing freely without letting the leaves rub against each other. If the leaves come into contact ("zero exposure"), they will generate friction, making it difficult to open the door and causing premature wear.
2. Allow painting/surface treatment: It provides space for multiple layers of paint, varnish, or other surface treatments without sticking leaves together.
3. Aesthetic consistency: Uniforms display a deliberate and professional appearance, indicating exquisite craftsmanship.
4. Reason for movement: Wood will expand and contract with changes in humidity. A small gap can accommodate such small movements without causing any problems.
How to achieve perfect 1/8 inch exposure
Exposure is a direct result of the depth and position of the tenon joint. The rules are as follows:
·The combined depth of two mortises (one inside the door and one inside the door frame) should be slightly greater than the thickness of a hinge piece.
·Formula: Door mortise depth+door frame mortise depth=hinge blade thickness+1/8 inches
Example: If your hinge plate thickness is 1/8 inch (0.125 inch):
·You can mortise and tenon the door to a depth of 1/16 inch (0.0625 inch).
·Connect the side pillar tenon to a depth of 1/8 inch (0.125 inch).
·Total mortise depth: 0.0625 inches+0.125 inches=0.1875 inches
·Thickness of hinge+display: 0.125 inches+0.0625 inches=0.1875 inches
This creates a perfect 1/16 inch groove for the hinges on both sides, totaling 1/8 inch.
Common Reveal Problems & Solutions
| Problem | Cause | Solution |
|---|---|---|
| No Reveal (Leaves Touch) | Mortises cut too shallow | Deepen one or both mortises slightly with a chisel |
| Too Much Reveal (Wide Gap) | Mortises cut too deep | Place a thin cardboard shim behind the hinge leaf in the deeper mortise |
| Uneven Reveal (Wider at Top/Bottom) | Mortises not aligned or door/jamb is out of plane | Check door and frame for plumb. The mortise on the high side may need to be deepened |
Exceptions to the 1/8 "rule
Heavy duty commercial/industrial doors: The opening may be slightly larger (e.g. 3/16 inch) to ensure that it will never get stuck under heavy loads.
Decorative or surface mounted hinges: Due to their lack of mortise and tenon joints, the exposed portion is determined by the hinge's own design - usually larger and part of the decorative appearance.
Non mortise (full surface) hinges: These hinges have a built-in hinge, typically about 1/4 inch or more, as the entire hinge is located on the surface of the wood.
Professional tips for inspection work
Use a feeler gauge or 1/8-inch drill bit Handle as an accurate measuring tool. After installation, insert all screws into the exposed gaps at the top, middle, and bottom of the hinge before fully tightening them. This allows for final fine-tuning.
Summary:
Maintain a consistent 1/8 inch (3mm) exposure on the mortise and tenon joint hinge. This' golden rule 'ensures smooth operation, adapts to surface treatment, and is a sign of precise and professional installation. This is achieved by cutting the combined mortise and tenon depth to exactly the thickness of one hinge piece plus 1/8 inch.
