Understanding tool cutting speeds and feed rates, more commonly referred to as "speeds and feeds," is essential before operating a cutting tool. Every milling process uses feeds and speeds, which vary for each tool depending on cutter diameter, operation, material, etc. Before you begin machining, it is essential to understand the appropriate feeds and speeds for your tool and operation.

The initial step is to define each of these elements. As measured in SFM (surface feet per minute), cutting speed is the difference in speed between the tool and the workpiece, also called surface speed. SFM is based on the different characteristics of the supplied material. The diameter of the cutting tool and the SFM determine the rotations per minute (RPM), a unit of speed.

Although speeds and feeds are frequently utilized in cutter programming, other factors also impact the best running parameters. The cutter's feed rate, expressed in inches per minute, is calculated using the cutter's speed (IPM).

A key concern in the machining process is chip load, which refers to the size of the chips generated during cutting. The highest chip load possible maximizes output, reduces heat, and avoids early dulling. A low chip load causes the bits to become overheated and dull more quickly. The tool will deflect if there is too much chip load, resulting in poor surface quality and, in severe cases, breaking or chipping.

What is the difference between chip load per tooth and chip load per tool?

• The amount of material effectively removed by all of a tool's cutting blades during a single revolution is known as "chip load per tool." Inches Per Revolution (IPR) is the unit of measurement.

• During each tool rotation, one cutting edge should remove the recommended amount of material per tooth, expressed as Inches Per Tooth (IPT).

Cutting Parameters

Removal of Materials Rate

Though this is not a component of the cutting tool's program, material removal rate (MRR) helps determine a tool's efficiency. Two essential running parameters that are taken into account by MRR are the axial depth of cut (ADOC), which is the distance a tool engages a workpiece along its centerline. The radial depth of cut (RDOC) is the distance a tool is stepping over into a workpiece.

The depth of cuts made by the tool and the rate at which it is cutting determine the number of cubic inches removed from a workpiece per minute (in3/min).

Speeds and Feeds In Practice

While the tool and the material of the workpiece determine many cutting parameters, the tool's feed rate is also influenced by the depths of the cuts. The operations performed are often categorized as slotting, roughing, and finishing, although there are many other, more specialized operations that determine the depth of cuts.

Guidelines for choosing the suitable parameters to run

1. Select the material that will be machined.
2. Select the appropriate FPT for that material based on the diameter of your mill. FPT is expressed in millimeters per tooth or inches per tooth (IPT) (MMPT).
3. Select the appropriate chip load factor (CLF) based on the radial depth of the cut.
4. Select the appropriate surface meters per minute (SMP) or surface feet per minute (SFM) (SMM)
5. To determine the RPM of your machine, multiply the SFM by the mill's diameter.
6. To compute the feed rate or IPM, multiply the RPM by the IPT, CLF, and the number of flutes.
7. If you want to be cautious, pick an SFM slightly lower but always go with the suggested FPT.

Calculations are valuable benchmarks for efficiently operating a cutting tool across various applications and materials. To determine the tool's initial specifications, however, you should refer to the manufacturer's specifications. The ideal operating parameters will also depend on the set-up, tool, machine, and material and will be determined by the machinist using their eyes and experience.

The proper cutting parameters must be determined to succeed in any metal-cutting process. For detailed advice on computations that will enable the tools you use to function as intended, contact SCTools.

If you have any questions about carbide cutting tools, end mills, drills, etc. be sure to reach out to us @ sctools.co/Home or call us at (877)737-0987. We help you machine better!