A #9 drill measures 0.1960 inch (4.978 mm). The closest fractional drill is 13/64" (0.2031") and the closest metric drill is 5.0 mm (0.1969").
What are the #9 drill equivalents?
| Drill | System | Decimal (in) | mm | Difference (in) |
|---|---|---|---|---|
| #9 | number | 0.1960 | 4.978 | 0 |
| #10 | number | 0.1935 | 4.915 | -0.0025 |
| 5.0 mm | metric | 0.1969 | 5.000 | +0.0009 |
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 #9 drill run?
| Material | RPM (HSS) | Feed (in/rev) |
|---|---|---|
| 6061-T6 aluminum | 3,898 | 0.0039 |
| 360 free-machining brass | 2,923 | 0.0035 |
| 1018 cold rolled steel | 1,559 | 0.0029 |
| 304 stainless steel | 780 | 0.0020 |
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 #9 drill in inches?
0.1960 inch, which is 4.978 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, 5.0 mm is within 0.0009 inch.
What tap uses a #9 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.