#Interhinge Hardware #Door and Window Hardware

The screw holes of friction stay hinges are designed as either circular or oval, mainly based on comprehensive considerations of installation convenience, adjustment requirements, and structural functions. The specific reasons are analyzed as follows:

I. Functional Differences of Screw Hole Shapes

(1) Circular Screw Holes: Mainly for Fixed Positioning

• Characteristics: Fixed hole diameter, with relatively stable positioning after the screw is tightened.
• Application Scenarios:
  • Installation scenarios without adjustment needs: When the positioning accuracy of door/window frames or installation components is high, circular holes can directly fix the hinge to ensure it works stably in the preset position (e.g., installation of standard-size doors/windows).
  • Structures with uniform force bearing: Circular holes can evenly distribute the tightening force of screws, suitable for withstanding pressure or tension perpendicular to the installation surface, ensuring a tight connection between the hinge and the installation surface.
• Typical Case: For hinge installation of ordinary casement windows, if the processing accuracy of the window frame and sash is sufficient, circular holes can be used for direct fixing without subsequent position adjustment.

(2) Oval Screw Holes: Reserved Adjustment Space

• Characteristics: The hole shape is long-strip, usually extending in a specific direction (e.g., horizontal or vertical), allowing the screw to move within a small range in the hole.
• Application Scenarios:
  • Compensation for installation errors: When there are dimensional deviations in door/window frames or installation surfaces, oval holes allow screws to move within the holes to adjust the hinge position, avoiding poor opening/closing of doors/windows or loose sealing caused by errors.
  • Fine-tuning during use: For example, if doors/windows are deformed after long-term use, the hinge position can be readjusted through oval holes to restore the normal opening/closing function of doors/windows.
  • Multi-angle installation requirements: Some special doors/windows (such as special-shaped windows or windows requiring multi-angle opening) need the hinge position to have certain flexibility, which can be satisfied by oval holes.
• Typical Case: During the installation of aluminum alloy doors/windows, due to possible errors in wall construction or profile processing, oval holes allow installers to move the hinge horizontally or vertically to ensure the consistent compression of the sealing rubber strip when the door/window is closed.

II. Core Logic Behind the Design

(1) Installation Convenience and Error Tolerance

• Circular holes: Suitable for standardized production and quick installation, but require high installation accuracy. If the installation surface has large errors, it may cause screws to fail to align or doors/windows to shift.
• Oval holes: Reduce installation difficulty and allow a certain “error tolerance space”, especially suitable for scenarios with possible dimensional deviations in on-site construction (such as uneven building walls, profile cutting errors, etc.).

(2) Functional Requirements and Structural Adaptability

• If the hinge needs to bear fixed load without adjustment, circular holes are sufficient; if the hinge needs to adjust the position after installation or during use (such as levelness, verticality, opening angle), oval holes are a better choice.
• For example, the friction stay hinge not only connects but also supports the weight of the window sash. In some scenarios, the oval holes are used to adjust the height or left-right position of the window sash to avoid friction with the window frame.

(3) Balance Between Cost and Production Process

• Circular holes are simple to process (drilling only), suitable for mass production with lower costs; oval holes require special molds or processing techniques (such as milling), with slightly higher costs. Therefore, manufacturers choose the hole shape according to product positioning:
  • Economical doors/windows or standardized components mostly use circular holes;
  • Mid-to-high-end doors/windows or components requiring flexible adjustment (such as broken bridge aluminum doors/windows, curtain wall hinges) mostly use oval holes.

III. Common Combinations in Practical Applications

• Hybrid usage scenarios: Some friction stay hinges are designed with both circular and oval holes. For example:
  • The fixed end (e.g., window frame side) uses circular holes to ensure the stability of the hinge base;
  • The movable end (e.g., window sash side) uses oval holes to facilitate adjusting the window sash position.
• Direction design: The long axis of the oval hole is usually consistent with the adjustment direction. For example:
  • Oval holes for horizontal adjustment have a horizontal long axis, used to adjust the left-right position of doors/windows;
  • Oval holes for vertical adjustment have a vertical long axis, used to adjust the height of doors/windows.

Summary

The choice of screw hole shape for friction stay hinges is essentially a match between “functional requirements and installation scenarios”:

• Circular holes represent “fixation and standardization”, suitable for scenarios with high precision and no adjustment needs;
• Oval holes represent “flexibility and error tolerance”, suitable for scenarios requiring error compensation or post-installation adjustment.
  This design difference not only reflects the engineering practicality of door/window hardware but also reflects the balance thinking of the manufacturing industry between standardization and flexibility.