A letter l drill measures 0.2900 inch (7.366 mm). The closest fractional drill is 19/64" (0.2969") and the closest metric drill is 7.4 mm (0.2913").
What are the letter l drill equivalents?
| Drill | System | Decimal (in) | mm | Difference (in) |
|---|---|---|---|---|
| L | letter | 0.2900 | 7.366 | 0 |
| 7.3 mm | metric | 0.2874 | 7.300 | -0.0026 |
| 7.4 mm | metric | 0.2913 | 7.400 | +0.0013 |
Drill sets that include this size
Number and letter sizes come in indexed sets; buy the set rather than single drills.
What speed should a letter l drill run?
| Material | RPM (HSS) | Feed (in/rev) |
|---|---|---|
| 6061-T6 aluminum | 2,634 | 0.0058 |
| 360 free-machining brass | 1,976 | 0.0052 |
| 1018 cold rolled steel | 1,054 | 0.0043 |
| 304 stainless steel | 527 | 0.0029 |
Starting points from conservative HSS drilling speeds. Small drills often call for more RPM than a benchtop drill press offers; run at the top speed and feed gently. Use cutting oil in steel and stainless, and clamp the work: never hold it by hand.
Cutting fluid for drilling
Frequently asked questions
What is a letter l drill in inches?
0.2900 inch, which is 7.366 mm. Letter drills run from A (0.234 inch) to Z (0.413 inch), continuing upward from the number drills. If you do not have this exact size, 7.4 mm is within 0.0013 inch.
What tap uses a letter l drill?
No common UNC or UNF thread uses it as its standard 75% tap drill, but it often serves as an alternative drill for a slightly different percentage of thread, or as a clearance or pilot size. The tap drill chart lists every standard pairing.