Countersink Size Chart
Find body drill, countersink diameter, angle, and pilot hole for flat head screws from #2 to 1/2″. Covers both 82° and 90° countersinks.
Countersink Drill Size Reference Table
| SCREW SIZE | HEAD TYPE | BODY DRILL (IN) | COUNTERSINK DIA (IN) | COUNTERSINK ANGLE | PILOT HOLE (IN) |
| #2 | Flat Head | 0.089 | 0.197 | 82° | 0.073 |
| #4 | Flat Head | 0.116 | 0.225 | 82° | 0.089 |
| #6 | Flat Head | 0.144 | 0.279 | 82° | 0.104 |
| #8 | Flat Head | 0.170 | 0.322 | 82° | 0.125 |
| #10 | Flat Head | 0.196 | 0.373 | 82° | 0.141 |
| #12 | Flat Head | 0.221 | 0.420 | 82° | 0.166 |
| 1/4″ | Flat Head | 0.257 | 0.477 | 82° | 0.196 |
| 5/16″ | Flat Head | 0.323 | 0.567 | 82° | 0.252 |
| 3/8″ | Flat Head | 0.386 | 0.682 | 82° | 0.302 |
| 7/16″ | Flat Head | 0.453 | 0.788 | 82° | 0.368 |
| 1/2″ | Flat Head | 0.520 | 0.894 | 82° | 0.422 |
| #2 | Flat Head | 0.089 | 0.185 | 90° | 0.073 |
| #4 | Flat Head | 0.116 | 0.212 | 90° | 0.089 |
| #6 | Flat Head | 0.144 | 0.263 | 90° | 0.104 |
| #8 | Flat Head | 0.170 | 0.305 | 90° | 0.125 |
| #10 | Flat Head | 0.196 | 0.352 | 90° | 0.141 |
| #12 | Flat Head | 0.221 | 0.398 | 90° | 0.166 |
| 1/4″ | Flat Head | 0.257 | 0.452 | 90° | 0.196 |
| 5/16″ | Flat Head | 0.323 | 0.538 | 90° | 0.252 |
| 3/8″ | Flat Head | 0.386 | 0.648 | 90° | 0.302 |
| 7/16″ | Flat Head | 0.453 | 0.750 | 90° | 0.368 |
| 1/2″ | Flat Head | 0.520 | 0.851 | 90° | 0.422 |
Quick Answer: What Countersink Size Do I Use?
A countersink is the cone-shaped recess that lets a flat head screw sit flush with the surface. To size it, match the countersink diameter to the screw head and pick the right included angle: use 82° for inch screws (ANSI) and 90° for metric screws (ISO). The countersink diameter should equal the screw head diameter so the head finishes level with the part.
This chart lists countersink sizes for flat head screws from #2 to 1/2″ at both 82° and 90°. For each screw it gives the body drill diameter (clearance for the screw shank), the countersink diameter, the included angle and the pilot hole size for the threads. Filter by angle or search by screw size.
Common 82° sizes: #6 → 0.279″ countersink, 0.144″ body drill | #8 → 0.322″ | #10 → 0.373″ | 1/4″ → 0.477″ | 3/8″ → 0.682″ | range 0.197–0.894″ across #2–1/2″. Use 90° for metric flat head screws.
Notes on This Chart
A countersink is the cone-shaped recess that lets a flat head screw sit flush with the surface. To size it, match the countersink diameter to the screw head and pick the right included angle: use 82° for inch screws (ANSI) and 90° for metric screws (ISO). The countersink diameter should equal the screw head diameter so the head finishes level with the part.
This chart lists countersink sizes for flat head screws from #2 to 1/2″ at both 82° and 90°. For each screw it gives the body drill diameter (clearance for the screw shank), the countersink diameter, the included angle and the pilot hole size for the threads. Filter by angle or search by screw size.
Common 82° sizes: #6 → 0.279″ countersink, 0.144″ body drill | #8 → 0.322″ | #10 → 0.373″ | 1/4″ → 0.477″ | 3/8″ → 0.682″ | range 0.197–0.894″ across #2–1/2″. Use 90° for metric flat head screws.
Need Flush Countersunk Panels Machined?
We machine flush panels, mounting brackets, and enclosures with standard countersink angles (82°, 90°, 100°) for a perfectly flush hardware fit. Upload your CAD models for a quote.
Frequently Asked Questions
What is the difference between 82° and 90° countersinks?
An 82° countersink is commonly used for inch-based flat head screws under ANSI standards. A 90° countersink is typically used for metric flat head screws following ISO standards. Choosing the wrong angle can prevent the screw head from sitting properly flush with the surface.
How do I determine the correct countersink depth?
The correct depth allows the flat head screw to sit level with or slightly below the workpiece surface. Use the countersink diameter as the reference for matching the screw head size, and adjust the depth based on the required finish.
What is the difference between a body drill and a pilot hole?
A body drill creates a clearance hole that allows the screw shank to pass through without engaging the threads. A pilot hole is smaller and guides the screw threads into the mating material, helping prevent splitting and improving screw alignment.
Can countersink holes be machined with CNC equipment?
Yes. CNC milling machines can create accurate countersink holes using countersink cutters or chamfer tools. Proper control of cutting depth, spindle speed, and feed rate ensures a smooth surface finish and consistent screw fit.
