metric (mm)
8
8 mm · 0.315 in
8 drill bit — 8 mm
The 8 bit measures 8 mm (0.315 in). The closest bits in the other series are 20/64, #1, O.
- Diameter
- 8 mm
- In inches
- 0.315 in
- Cross-section
- 50.27 mm²
Closest in other series
Use this when the only bits at hand belong to another series. For tapping, prefer the slightly smaller bit over the slightly larger one — a hole can be opened up later, never closed.
One step up and down
metric (mm)
Metric bits state the millimetres outright, inch bits state sixty-fourths. Number and letter bits carry names inherited from old wire gauges, where no formula links the label to the size.
0.10.10.20.20.30.30.40.40.50.50.60.60.70.70.80.80.90.9111.21.21.251.251.41.41.61.61.81.8222.052.052.22.22.42.42.52.52.62.62.82.8333.23.23.33.33.43.43.63.63.83.8444.24.24.44.44.54.54.64.64.84.8555.25.25.45.45.55.55.65.65.85.8666.56.56.86.8777.57.5888.58.5999.59.5101010.210.210.510.5111111.511.5121212.512.51313
How to read this
- Inch bits are counted in sixty-fourths — 16/64 reduces to 1/4.
- Higher numbers are thinner; later letters are thicker, with A picking up above #1.
- An inch is 25.4 mm, so multiply the inch value by 25.4 to get millimetres.
- For tapping, drill with the bit nearest to the thread’s outside diameter minus its pitch.
Frequently asked questions
Q. How wide is the 8 bit?
8 mm, or 0.315 inches.
Q. What would I use from another series?
The closest are 20/64 (7.938 mm), #1 (5.791 mm), O (8.026 mm).
Q. Which threads can this size tap?
None of the metric threads in this table match closely enough.
Q. What is the cross-section?
50.27 mm².