What is the correct RPM for a 0.750 diameter high-speed steel end mill machining O1 tool steel at 50 SFM?

To determine the correct RPM for a 0.750 diameter high-speed steel end mill machining O1 tool steel at 50 SFM (Surface Feet per Minute), you can use the formula:

[

\text{RPM} = \frac{\text{SFM} \times 12}{\pi \times D}

]

Where:

• SFM is the cutting speed in surface feet per minute.

• D is the diameter of the tool in inches.

Plugging the values into the formula involves:

1. Converting the SFM to inches: Since there are 12 inches in a foot, multiplying SFM (50) by 12 gives you 600 inches per minute (IPM).

2. Calculating the circumference of the end mill by using its diameter: For a 0.750 inch diameter end mill, you calculate:

[

\pi \times 0.750 \approx 2.3562 \text{ inches}

]

3. Finally, substituting into the RPM equation gives:

[

\text{RPM} = \frac{600}{2.3562} \approx 254.6

]

When rounding to a standard value, approximately