Number drill · #33
#33 Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes
https://shopmath.org/drills/number/33 · data verified August 1, 2026
A #33 drill bit is 0.1130 in (2.870 mm) in diameter. It is the tap drill for #6-40 UNF at 75% thread engagement with a cut tap, where it leaves 77.0% thread. The nearest fractional size is 7/64" at 0.1094 in. Diameters are nominal.
- Series
- Number
- Designation
- #33
- Inch
- 0.1130
- mm
- 2.870
- Standard
- ANSI/ASME B94.11M
Number Drill · #33 · nominal diameter
0.1130 in
- Millimetre
- 2.870mm
- Taps
- #6-40 UNF
Nominal diameter. As a tap drill it leaves 77.0% thread in #6-40 UNF with a cut tap.
#33 Drill Bit Size in Inches and Millimetres
The nominal diameter of a #33 drill bit. Drill sizes are nominal — a worn drill, run-out or a soft material that closes in behind the cut all move the finished hole.
| Property | Value |
|---|---|
| Diameter, decimal inch | 0.1130 in |
| Diameter, millimetre | 2.870 mm |
| Cross-sectional area | 0.01003 in² |
1 in = 25.4 mm exactly, so the two columns are the same value in different units, not two measurements.
Threads a #33 Drill Bit Taps
Every thread in this reference whose tap drill is the #33 drill bit, and the thread engagement it leaves. The engagement asked for and the engagement the drill actually produces are different numbers — that gap is why both columns are here.
| Thread | Series | Thread % asked for | Thread % this drill leaves |
|---|---|---|---|
| #6-40 UNF | Unified Fine (UNF) | 75%default | 77.0 |
| #6-40 UNF | Unified Fine (UNF) | 80% | 77.0 |
| #6-32 UNC | Unified Coarse (UNC) | 60% | 61.6 |
Values are for cut taps. Rows marked default are the shop-default engagement for that thread.
Fasteners That Pass Through a #33 Drill Bit Hole
A hole drilled with a #33 drill bit is the standard clearance hole for these fasteners — the through-hole the bolt passes freely, not the tapped hole.
| Fastener | Series | Clearance class |
|---|---|---|
| #2-64 UNF | Unified Fine (UNF) | loose |
| #2-56 UNC | Unified Coarse (UNC) | loose |
| #3-56 UNF | Unified Fine (UNF) | normal |
| #3-48 UNC | Unified Coarse (UNC) | normal |
Clearance classes per ISO 273 (metric) and ASME B18.2.8 (inch): close for located joints, normal for general assembly, loose for slotted or adjustable joints.
#33 Drill Bit Equivalents in Every Other Drill Series
The closest size to the #33 drill bit in each of the other three indexes, with the difference in inches. None of them is the same drill — check the difference before substituting one into a tapped hole.
| Property | Property | Diameter | Property | |
|---|---|---|---|---|
| Drill | Series | in | mm | Difference, in |
| A | Letter | 0.2340 | 5.944 | +0.1210 |
| 7/64" | Fractional | 0.1094 | 2.778 | −0.0036 |
| 2.85 mm | Metric | 0.1122 | 2.850 | −0.0008 |
A positive difference means the equivalent drill is larger, which leaves less thread in a tapped hole. Sizes without a link are stored for the nearest-drill calculation but do not carry their own page.
Drill Sizes Either Side of the #33 Drill Bit
Ordered by diameter across all four indexes, so the next size up may be a letter, a fraction or a metric drill rather than the next one in this series.
Sources and Method for the #33 Drill Bit Size
- Drill diametercompiled
Number/letter: bd_warehouse drill_sizes.csv (Apache-2.0) cross-checked against Wikipedia Drill bit sizes (CC BY-SA 4.0). Fractional: computed 1/64 in steps per ANSI B94.11M. Metric: computed BS 328 increment pattern.
Verified against Wikipedia Drill bit sizes (CC BY-SA 4.0); 31/31 checks passed
Compiled from independent public sources that agree cell-for-cell.
- Tap drill usagecomputed+compiled
bd_warehouse drill_sizes.csv (Apache-2.0) + Wikipedia Drill bit sizes (CC BY-SA 4.0); fractional and metric computed from ANSI B94.11M / BS 328 increment patterns
Verified against drills: 31 checks passed across 1 harness(es)
Part computed from the standard's formulas, part compiled from agreeing public sources.
- Assumptions
- Diameters are nominal. Drill manufacturing tolerance, wear and run-out all cut oversize, and every one of those moves a tapped hole toward less thread than the table says.
- Tap drill usage assumes cut taps. #6-40 UNF at 75% requested engagement is what this drill is normally bought for.
- Dataset scope: Number sizes #61-#80 are stored but tagged demandTier 'extended' — query-space-map.md Appendix A found the tail thinning in the 60s. Sizes below #80 and metric sizes above 25.0 mm excluded.
- Data last verified
- August 1, 2026
How to Cite This #33 Drill Bit Reference
Citation
ShopMath. "#33 Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes." ShopMath, verified August 1, 2026, https://shopmath.org/drills/number/33
BibTeX
@misc{shopmath-drills-number-33,
title = {#33 Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes},
author = {{ShopMath}},
year = {2026},
howpublished = {\url{https://shopmath.org/drills/number/33}},
note = {Data verified 2026-08-01}
}Permanent URL
https://shopmath.org/drills/number/33
Common Questions About the #33 Drill Bit
What size is a #33 drill bit?
- A #33 drill bit is 0.1130 in in diameter, which is 2.870 mm.
What thread does a #33 drill bit tap?
- A #33 drill bit is the tap drill for #6-40 UNF at 75% requested thread engagement, where it leaves 77.0% thread with a cut tap.
What is the metric equivalent of a #33 drill bit?
- The closest metric drill to a #33 drill bit (2.870 mm) is 2.85 mm, which is 2.850 mm — 0.0008 in smaller.
What fraction is a #33 drill bit closest to?
- A #33 drill bit (0.1130 in) sits closest to the 7/64" fractional drill at 0.1094 in, a difference of 0.0036 in.
What bolt fits through a #33 drill bit hole?
- A hole drilled with a #33 drill bit is the standard loose clearance hole for #2-64 UNF, and a clearance hole for 3 other fastener sizes listed on this page.
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