A #42 drill measures 0.0935 inch (2.375 mm). The closest fractional drill is 3/32" (0.0938") and the closest metric drill is 2.4 mm (0.0945"). It is the standard tap drill for #4-48.
What are the #42 drill equivalents?
| Drill | System | Decimal (in) | mm | Difference (in) |
|---|---|---|---|---|
| #42 | number | 0.0935 | 2.375 | 0 |
| 2.3 mm | metric | 0.0906 | 2.300 | -0.0029 |
| 3/32" | fraction | 0.0938 | 2.381 | +0.0003 |
| 2.4 mm | metric | 0.0945 | 2.400 | +0.0010 |
| #41 | number | 0.0960 | 2.438 | +0.0025 |
Tap drill for: #4-48.
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 #42 drill run?
| Material | RPM (HSS) | Feed (in/rev) |
|---|---|---|
| 6061-T6 aluminum | 8,171 | 0.0019 |
| 360 free-machining brass | 6,128 | 0.0017 |
| 1018 cold rolled steel | 3,268 | 0.0014 |
| 304 stainless steel | 1,634 | 0.0009 |
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 #42 drill in inches?
0.0935 inch, which is 2.375 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, 2.4 mm is within 0.0010 inch.
What tap uses a #42 drill?
It is the standard 75% thread tap drill for #4-48. Tap drills are chosen to leave about 75% of full thread depth, the balance of strength and tapping torque that published charts use.