A #45 drill measures 0.0820 inch (2.083 mm). The closest fractional drill is 5/64" (0.0781") and the closest metric drill is 2.1 mm (0.0827"). It is the standard tap drill for #3-56.
What are the #45 drill equivalents?
| Drill | System | Decimal (in) | mm | Difference (in) |
|---|---|---|---|---|
| #45 | number | 0.0820 | 2.083 | 0 |
| #46 | number | 0.0810 | 2.057 | -0.0010 |
| 2.1 mm | metric | 0.0827 | 2.100 | +0.0007 |
Tap drill for: #3-56.
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 #45 drill run?
| Material | RPM (HSS) | Feed (in/rev) |
|---|---|---|
| 6061-T6 aluminum | 9,316 | 0.0016 |
| 360 free-machining brass | 6,987 | 0.0015 |
| 1018 cold rolled steel | 3,727 | 0.0012 |
| 304 stainless steel | 1,863 | 0.0008 |
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 #45 drill in inches?
0.0820 inch, which is 2.083 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, 2.1 mm is within 0.0007 inch.
What tap uses a #45 drill?
It is the standard 75% thread tap drill for #3-56. Tap drills are chosen to leave about 75% of full thread depth, the balance of strength and tapping torque that published charts use.