A #50 drill measures 0.0700 inch (1.778 mm). The closest fractional drill is 1/16" (0.0625") and the closest metric drill is 1.8 mm (0.0709"). It is the standard tap drill for #2-56 and #2-64.
What are the #50 drill equivalents?
| Drill | System | Decimal (in) | mm | Difference (in) |
|---|---|---|---|---|
| #50 | number | 0.0700 | 1.778 | 0 |
| 1.8 mm | metric | 0.0709 | 1.800 | +0.0009 |
| #49 | number | 0.0730 | 1.854 | +0.0030 |
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 #50 drill run?
| Material | RPM (HSS) | Feed (in/rev) |
|---|---|---|
| 6061-T6 aluminum | 10,913 | 0.0014 |
| 360 free-machining brass | 8,185 | 0.0013 |
| 1018 cold rolled steel | 4,365 | 0.0011 |
| 304 stainless steel | 2,183 | 0.0007 |
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 #50 drill in inches?
0.0700 inch, which is 1.778 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, 1.8 mm is within 0.0009 inch.
What tap uses a #50 drill?
It is the standard 75% thread tap drill for #2-56 and #2-64. Tap drills are chosen to leave about 75% of full thread depth, the balance of strength and tapping torque that published charts use.