A #19 drill measures 0.1660 inch (4.216 mm). The closest fractional drill is 11/64" (0.1719") and the closest metric drill is 4.2 mm (0.1654").
What are the #19 drill equivalents?
| Drill | System | Decimal (in) | mm | Difference (in) |
|---|---|---|---|---|
| #19 | number | 0.1660 | 4.216 | 0 |
| 4.2 mm | metric | 0.1654 | 4.200 | -0.0006 |
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 #19 drill run?
| Material | RPM (HSS) | Feed (in/rev) |
|---|---|---|
| 6061-T6 aluminum | 4,602 | 0.0033 |
| 360 free-machining brass | 3,452 | 0.0030 |
| 1018 cold rolled steel | 1,841 | 0.0025 |
| 304 stainless steel | 920 | 0.0017 |
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 #19 drill in inches?
0.1660 inch, which is 4.216 mm. Number drills get smaller as the number rises, so the next number up is a smaller drill. If you do not have this exact size, 4.2 mm is within 0.0006 inch.
What tap uses a #19 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.