Countersunk Hole Size Chart for Socket Flat Head Screws (ANSI Metric)
ANSI Metric countersunk hole size chart for socket flat head screws, including pilot hole diameters for close, normal, and loose fits, countersink diameters, and angles
Socket Flat Head Screw Countersunk Hole Chart (ANSI Metric)
| Fastener Size (Thread) | Pilot Hole Diameter (mm) | Countersink Diameter (mm) | Countersink Angle (°) | ||
|---|---|---|---|---|---|
| Close Fit H12 | Normal Fit H13 | Loose Fit H14 | |||
| M3 | 3.2 | 3.4 | 3.6 | 6.94 | 90 |
| M3.5 | 3.7 | 3.9 | 4.2 | 6.94 | 90 |
| M4 | 4.3 | 4.5 | 4.8 | 9.18 | 90 |
| M5 | 5.3 | 5.5 | 5.8 | 11.47 | 90 |
| M6 | 6.4 | 6.6 | 7 | 13.71 | 90 |
| M8 | 8.4 | 9 | 10 | 18.25 | 90 |
| M10 | 10.5 | 11 | 12 | 22.73 | 90 |
| M12 | 13 | 13.5 | 14.5 | 27.21 | 90 |
| M16 | 17 | 17.5 | 18.5 | 33.99 | 90 |
| M20 | 21 | 22 | 24 | 40.71 | 90 |
| M24 | 25 | 26 | 28 | 41 | 90 |
About ANSI Metric Countersunk Hole Sizes for Socket Flat Head Screws
This ANSI Metric countersunk hole size chart for socket flat head screws provides standardized dimensions in millimeters according to the ANSI Metric standard. It lists recommended pilot hole diameters for close fit (H12), normal fit (H13), and loose fit (H14), along with the corresponding countersink diameters and standard 90° countersink angles.
Using accurate ANSI Metric countersunk hole dimensions ensures proper screw seating, flush head alignment, and reliable mechanical performance in metric fastening applications. This reference is essential for engineers, machinists, and designers working with ANSI Metric socket flat head screws, including:
- Mechanical and product design projects requiring ANSI Metric socket flat head screws in metric systems.
- Machining, drilling, and fabrication processes that need precise pilot hole and countersink preparation for standard socket flat head screws.
- Assembly and quality control operations ensuring proper fit, alignment, and flush seating of socket flat head screw heads.
Key Terms in the ANSI Metric Socket Flat Head Screw Countersunk Hole Chart
- Pilot Hole Diameter (H12 / H13 / H14): The drilled hole diameter defining screw clearance, categorized by tolerance grade for close, normal, or loose fit.
- Countersink Diameter: The circular conical recess machined to allow the ANSI Metric socket flat head screw to sit flush with the surface.
- Countersink Angle: The included angle of the conical recess, typically 90° for standard ANSI Metric flat head screws.
- ANSI Metric Standard: The American National Standards Institute (ANSI) Metric specification defining dimensions, tolerances, and geometry for metric-series socket flat head screws.
Referencing this ANSI Metric socket flat head screw countersunk chart ensures consistent part design, precise manufacturing, and compliance with international metric fastener standards. Proper use of these dimensions improves assembly quality, reduces machining errors, and enhances the reliability of mechanical systems.