A #38 drill measures 0.1015 inch (2.578 mm). The closest fractional drill is 3/32" (0.0938") and the closest metric drill is 2.6 mm (0.1024"). It is the standard tap drill for #5-40.
What are the #38 drill equivalents?
| Drill | System | Decimal (in) | mm | Difference (in) |
|---|---|---|---|---|
| #38 | number | 0.1015 | 2.578 | 0 |
| #39 | number | 0.0995 | 2.527 | -0.0020 |
| 2.6 mm | metric | 0.1024 | 2.600 | +0.0009 |
| #37 | number | 0.1040 | 2.642 | +0.0025 |
Tap drill for: #5-40.
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 #38 drill run?
| Material | RPM (HSS) | Feed (in/rev) |
|---|---|---|
| 6061-T6 aluminum | 7,527 | 0.0020 |
| 360 free-machining brass | 5,645 | 0.0018 |
| 1018 cold rolled steel | 3,011 | 0.0015 |
| 304 stainless steel | 1,505 | 0.0010 |
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 #38 drill in inches?
0.1015 inch, which is 2.578 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, 2.6 mm is within 0.0009 inch.
What tap uses a #38 drill?
It is the standard 75% thread tap drill for #5-40. Tap drills are chosen to leave about 75% of full thread depth, the balance of strength and tapping torque that published charts use.