A #7 drill measures 0.2010 inch (5.105 mm). The closest fractional drill is 13/64" (0.2031") and the closest metric drill is 5.1 mm (0.2008"). It is the standard tap drill for 1/4-20.
What are the #7 drill equivalents?
| Drill | System | Decimal (in) | mm | Difference (in) |
|---|---|---|---|---|
| #7 | number | 0.2010 | 5.105 | 0 |
| #8 | number | 0.1990 | 5.055 | -0.0020 |
| 5.1 mm | metric | 0.2008 | 5.100 | -0.0002 |
| 13/64" | fraction | 0.2031 | 5.159 | +0.0021 |
| #6 | number | 0.2040 | 5.182 | +0.0030 |
Tap drill for: 1/4-20.
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 #7 drill run?
| Material | RPM (HSS) | Feed (in/rev) |
|---|---|---|
| 6061-T6 aluminum | 3,801 | 0.0040 |
| 360 free-machining brass | 2,851 | 0.0036 |
| 1018 cold rolled steel | 1,520 | 0.0030 |
| 304 stainless steel | 760 | 0.0020 |
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 #7 drill in inches?
0.2010 inch, which is 5.105 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, 5.1 mm is within 0.0002 inch.
What tap uses a #7 drill?
It is the standard 75% thread tap drill for 1/4-20. Tap drills are chosen to leave about 75% of full thread depth, the balance of strength and tapping torque that published charts use.