Counterbore Hole Size Chart for Pan Head Screws (ANSI Inch)
ANSI inch counterbore hole size chart for pan head screws, including pilot hole diameters for close, normal, and loose fits, counterbore diameters, and depths (inches)
Pan Head Screw Counterbore Hole Chart (ANSI Inch)
| Fastener Size | Pilot Hole Diameter (inches) | Counterbore Diameter (inches) | Counterbore Depth (inches) | ||
|---|---|---|---|---|---|
| Close Fit | Normal Fit | Loose Fit | |||
| #0 | 1/15 | 6/79 | 3/32 | 9/64 | 2/37 |
| #1 | 3/37 | 4/45 | 8/77 | 11/64 | 6/95 |
| #2 | 3/32 | 7/69 | 7/62 | 3/16 | 7/97 |
| #3 | 5/47 | 8/69 | 9/70 | 7/32 | 3/37 |
| #4 | 3/25 | 9/70 | 14/97 | 1/4 | 8/89 |
| #5 | 9/64 | 5/32 | 11/64 | 9/32 | 8/77 |
| #6 | 2/13 | 10/59 | 5/27 | 19/64 | 7/62 |
| #8 | 9/50 | 10/51 | 13/61 | 23/64 | 10/77 |
| #10 | 15/73 | 21/95 | 5/21 | 13/32 | 4/27 |
| #12 | 15/64 | 15/61 | 6/23 | 29/64 | 1/6 |
| 1/4 | 17/64 | 9/32 | 19/64 | 17/32 | 8/39 |
| 5/16 | 21/64 | 11/32 | 23/64 | 41/64 | 24/97 |
| 3/8 | 25/64 | 13/32 | 27/64 | 25/32 | 16/55 |
| 7/16 | 29/64 | 15/32 | 31/64 | 57/64 | 1/3 |
| 1/2 | 17/32 | 9/16 | 39/64 | 1 1/64 | 31/82 |
| 9/16 | 19/32 | 5/8 | 43/64 | 1 5/64 | 8/19 |
| 5/8 | 21/32 | 11/16 | 47/64 | 1 13/64 | 45/97 |
| 3/4 | 25/32 | 13/16 | 29/32 | 1 15/32 | 27/49 |
About ANSI Inch Counterbore Hole Sizes for Pan Head Screws
This ANSI inch counterbore hole size chart for pan head screws provides engineers, machinists, and designers with standard dimensions based on American National Standards Institute (ANSI) specifications. It lists the recommended pilot hole diameters for close fit, normal fit, and loose fit conditions, along with the corresponding counterbore diameters and counterbore depths in inches.
These ANSI counterbore dimensions ensure accurate screw seating, proper head clearance, and reliable mechanical performance in inch-based fastening systems. The chart supports design consistency and manufacturing precision across a wide range of engineering applications, including:
- Mechanical and product design projects using pan head machine screws conforming to ANSI inch standards.
- Machining and fabrication tasks requiring precise counterbore and pilot hole preparation for pan head fasteners.
- Quality assurance and assembly operations ensuring correct head fit and fastener alignment in mechanical components.
Key Terms in the ANSI Counterbore Hole Chart
- Pilot Hole Diameter: The drilled hole diameter that determines clearance or fit for the screw shank, typically categorized as close, normal, or loose fit.
- Counterbore Diameter: The circular recess machined to accommodate the screw head so it sits flush or slightly below the surface.
- Counterbore Depth: The vertical depth of the counterbore, matching the head height of the ANSI pan head screw.
- ANSI Standard: The American National Standards Institute specification defining the geometric and dimensional requirements for inch-series fasteners, including pan head screw dimensions.
Consulting the ANSI pan head screw counterbore hole size chart helps ensure dimensional consistency, optimal assembly quality, and compliance with inch-based engineering standards. Accurate reference to this data improves fit, reduces rework, and supports best practices in mechanical design and precision manufacturing.