A #33 drill measures 0.1130 inch (2.870 mm). The closest fractional drill is 7/64" (0.1094") and the closest metric drill is 2.9 mm (0.1142"). It is the standard tap drill for #6-40.
What are the #33 drill equivalents?
| Drill | System | Decimal (in) | mm | Difference (in) |
|---|---|---|---|---|
| #33 | number | 0.1130 | 2.870 | 0 |
| 2.8 mm | metric | 0.1102 | 2.800 | -0.0028 |
| #34 | number | 0.1110 | 2.819 | -0.0020 |
| 2.9 mm | metric | 0.1142 | 2.900 | +0.0012 |
Tap drill for: #6-40.
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 #33 drill run?
| Material | RPM (HSS) | Feed (in/rev) |
|---|---|---|
| 6061-T6 aluminum | 6,761 | 0.0023 |
| 360 free-machining brass | 5,070 | 0.0020 |
| 1018 cold rolled steel | 2,704 | 0.0017 |
| 304 stainless steel | 1,352 | 0.0011 |
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 #33 drill in inches?
0.1130 inch, which is 2.870 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, 2.9 mm is within 0.0012 inch.
What tap uses a #33 drill?
It is the standard 75% thread tap drill for #6-40. Tap drills are chosen to leave about 75% of full thread depth, the balance of strength and tapping torque that published charts use.