number drill bit
#29
0.1360" / 3.45 mm
Drill bit
- Decimal
- 0.1360"3.45 mm
- Nearest fraction
- 9/64"+0.0046"
- Nearest other system
- 3.5 mm+0.0018"
Full chart 307 rows
Sort any column, filter by series, print a shop sheet. Click a row to load it on the gauge.
Drill bit size chart
307 rowsDrill bit size chart · ScrewBoltChart
screwboltchart.com · inch-first · tap drills 75% (soft metals) · torque dry, K=0.20 · verify against the governing standard
| metric | 0.0118" | 0.30 | 1/64" · #80 | — | ||
| number | 0.0135" | 0.34 | 0.35 mm | — | ||
| metric | 0.0138" | 0.35 | 1/64" · #80 | — | ||
| number | 0.0145" | 0.37 | 0.35 mm | — | ||
| fraction | 0.0156" | 0.40 | 0.4 mm | — | ||
| metric | 0.0157" | 0.40 | 1/64" · 1/64" | — | ||
| number | 0.0160" | 0.41 | 0.4 mm | — | ||
| metric | 0.0177" | 0.45 | 1/64" · #77 | — | ||
| number | 0.0180" | 0.46 | 0.45 mm | — | ||
| metric | 0.0197" | 0.50 | 1/64" · #76 | — | ||
| number | 0.0200" | 0.51 | 0.5 mm | — | ||
| number | 0.0210" | 0.53 | 0.55 mm | — | ||
| metric | 0.0217" | 0.55 | 1/64" · #75 | — | ||
| number | 0.0225" | 0.57 | 0.55 mm | — | ||
| metric | 0.0236" | 0.60 | 1/32" · #73 | — | ||
| number | 0.0240" | 0.61 | 0.6 mm | — | ||
| number | 0.0250" | 0.64 | 0.65 mm | — | ||
| metric | 0.0256" | 0.65 | 1/32" · #71 | — | ||
| number | 0.0260" | 0.66 | 0.65 mm | — | ||
| metric | 0.0276" | 0.70 | 1/32" · #70 | — |
05 / Field guide
Every bit
has a number.
Drills come in four overlapping systems: fractional inch, number, letter and metric. Together they cover almost every size between 0.3 mm and an inch, and each one exists because some tap or clearance hole needs it.
Number and letter drills
Number drills run backwards, from #80 (0.0135") up to #1 (0.228"). Letter drills continue from A (0.234") to Z (0.413"). They fill the gaps between 1/64" fractions, which is why tap charts call for them: a #29 for an 8-32, an F for a 5/16"-18.
Fractional and metric
Fractional drills step in 1/64" (0.0156"). Metric jobber drills step in 0.1 mm up to 10 mm and 0.5 mm above. A metric set is effectively finer than a fractional one at small sizes, so it often contains a closer match for a tap drill.
1/64" = 0.015625" = 0.397 mm
Identifying a loose bit
Measure across the smooth shank, not the flutes. On screen, lay the bit across the V-gauge and slide it until it touches both edges; the cursor reads its diameter and the nearest standard size.
Choosing a drill set
A 29-piece fractional set (1/16" to 1/2" in 1/64" steps) covers most woodwork and clearance holes. For tapping, add a number set (#1 to #60) and a letter set: they hold the exact tap drills for nearly every UN thread. If you work in metric, a 1–10 mm set in 0.1 mm steps is the single most useful set you can buy, because it contains a close match for almost any inch or metric tap drill.
Drill sizes run slightly large
Twist drills cut slightly oversize, typically 0.02–0.05 mm in steel and more in soft or sticky metals, especially when they are worn or the hole is drilled freehand. For precise holes, drill undersize and ream to size.
Questions
Answered plainly.
01What size is a #29 drill?+−
0.136" (3.45 mm). It is the 75% tap drill for #8-32 and #8-36 threads.
02What size is an F drill?+−
0.257" (6.53 mm). It is the tap drill for 5/16"-18 and the close-fit clearance drill for a 1/4" screw.
03What is 13/64" in mm?+−
5.16 mm (0.2031"). It is the hardware-store substitute for a #7 drill when tapping 1/4"-20.
04What metric drill is closest to 1/4"?+−
6.4 mm (0.252") is the nearest, 0.05 mm over. 6.3 mm is 0.05 mm under.
05Why do number drills go backwards?+−
They come from the old Stubs steel wire gauge, where higher numbers meant thinner wire after more drawing passes.
06Are letter drills still used?+−
Yes, mainly as tap and clearance drills between 0.234" and 0.413", where 1/64" steps are too coarse for a good thread percentage.
07What size is a #7 drill?+−
0.201" (5.11 mm). It is the 75% tap drill for 1/4"-20 and the free-fit clearance drill for a #10 screw.
08What size is a #36 drill?+−
0.1065" (2.71 mm). It is the tap drill for #6-32.
09What drill size is 5 mm in inches?+−
0.197". The nearest inch drills are #9 (0.196") and 13/64" (0.203"). A 5 mm drill is the tap drill for M6 × 1.0.
10What size is a #43 drill?+−
0.089" (2.26 mm). It is the 75% tap drill for #4-40, giving about 71% thread.
11What size is a letter Q drill?+−
0.332" (8.43 mm). It is the tap drill for 3/8"-24 and the free-fit clearance drill for a 5/16" screw.
12How do I read the size on a drill bit?+−
Fractional and metric bits are stamped on the shank, usually near the end. Number and letter bits are stamped with the number or letter. If the marking is gone, measure the shank or use the V-gauge.