A #25 drill measures 0.1495 inch (3.797 mm). The closest fractional drill is 5/32" (0.1563") and the closest metric drill is 3.8 mm (0.1496"). It is the standard tap drill for #10-24.
What are the #25 drill equivalents?
| Drill | System | Decimal (in) | mm | Difference (in) |
|---|---|---|---|---|
| #25 | number | 0.1495 | 3.797 | 0 |
| #26 | number | 0.1470 | 3.734 | -0.0025 |
| 3.8 mm | metric | 0.1496 | 3.800 | +0.0001 |
| #24 | number | 0.1520 | 3.861 | +0.0025 |
Tap drill for: #10-24.
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 #25 drill run?
| Material | RPM (HSS) | Feed (in/rev) |
|---|---|---|
| 6061-T6 aluminum | 5,110 | 0.0030 |
| 360 free-machining brass | 3,832 | 0.0027 |
| 1018 cold rolled steel | 2,044 | 0.0022 |
| 304 stainless steel | 1,022 | 0.0015 |
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 #25 drill in inches?
0.1495 inch, which is 3.797 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, 3.8 mm is within 0.0001 inch.
What tap uses a #25 drill?
It is the standard 75% thread tap drill for #10-24. Tap drills are chosen to leave about 75% of full thread depth, the balance of strength and tapping torque that published charts use.