At what RPM should a 1/8" drill bit be set to drill aluminum at 300 surface feet per minute (SFM)?

To determine the optimal RPM for drilling aluminum with a 1/8" drill bit at a specific surface speed, you can use the formula for calculating RPM based on surface feet per minute (SFM). The formula is:

[ \text{RPM} = \frac{\text{SFM} \times 12}{\pi \times \text{Diameter (inches)}} ]

In this case, you want to drill at 300 SFM with a drill bit that has a diameter of 1/8", which is 0.125 inches.

Substituting the values into the formula gives:

[ \text{RPM} = \frac{300 \times 12}{\pi \times 0.125} ]

Calculating the denominator:

• (\pi \times 0.125 \approx 0.3927)

Now, substituting back into the RPM equation:

[ \text{RPM} = \frac{3600}{0.3927} \approx 9177 ]

Rounding it leads to an appropriate setting close to 9600 RPM, which is the correct choice.

The reason this RPM calculation is significant is that it helps ensure efficient drilling without causing damage to