A #22 drill measures 0.1570 inch (3.988 mm). The closest fractional drill is 5/32" (0.1563") and the closest metric drill is 4.0 mm (0.1575").
What are the #22 drill equivalents?
| Drill | System | Decimal (in) | mm | Difference (in) |
|---|---|---|---|---|
| #22 | number | 0.1570 | 3.988 | 0 |
| 5/32" | fraction | 0.1563 | 3.969 | -0.0007 |
| 4.0 mm | metric | 0.1575 | 4.000 | +0.0005 |
| #21 | number | 0.1590 | 4.039 | +0.0020 |
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 #22 drill run?
| Material | RPM (HSS) | Feed (in/rev) |
|---|---|---|
| 6061-T6 aluminum | 4,866 | 0.0031 |
| 360 free-machining brass | 3,649 | 0.0028 |
| 1018 cold rolled steel | 1,946 | 0.0024 |
| 304 stainless steel | 973 | 0.0016 |
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 #22 drill in inches?
0.1570 inch, which is 3.988 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, 4.0 mm is within 0.0005 inch.
What tap uses a #22 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.