KEVOS® MAKEOS · Manufacturing
Drill Sizes: Number, Letter, Fraction and Metric
What is the decimal size of this number or letter drill, or which drills are closest to a size?
Decimal inch and millimetre size of number (1–80) and letter (A–Z) drills, and the nearest number, letter, fractional (1/64) and metric (0.1 mm) drills to any diameter.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Look up | choice | Find drills near a size, or the size of a drill designation. |
| Diameter | mm or in | Required hole or drill diameter. |
| Unit of diameter | choice | Unit of the diameter. |
| Drill designation | choice | Number or letter drill to look up. |
Method and formulas
- Number and letter drill sizes are the standard decimal equivalents (ASME B94.11M).
- Fractional drills in 1/64 in steps; metric drills in 0.1 mm steps.
- The closest drill in each series is reported with its difference from the required size.
- Example: the nearest drills to 6.8 mm are No. 1, Letter H, 17/64 in, 6.8 mm.
Limitations
- Drills cut slightly oversize; check the hole for close tolerances.
- Availability of sizes varies by supplier.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Find the size of a number or letter drill
- Find the nearest available drill to a calculated hole size
- Convert between drill series
Who it is for
- Machinists
- Toolmakers
- Maintenance fitters
What you get
- Nearest number, letter, fractional and metric drills
- Decimal size of a designation
- Difference from the required size
Interpreting the result
- For tapping, use the tap drill tool to choose the size first, then find the nearest drill here.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2695, 1015–1016. Topic reference; no source tables or recommended settings are reproduced.
- ASME B94.11M Twist Drills
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