When performing machining operations, it is important to ensure the calculated chip load for your setup lies in the corresponding range of optimal chip load from this table.

Chip load is defined as the thickness of the chips removed during a machining operation. Chip Load = Feed Rate (inches per minute) / (RPM x number of flutes). Setting machining parameters to ensure optimal chip load improves machining quality and prolongs tool life.

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Optimal chip load determines the maximum feed per tooth while ensuring minimum tool wear. Cutting hard material requires a stronger shear force and hence when cutting through the same thickness of the workpiece, hard materials exert a greater load on the cutting edge, compared to softer materials. Therefore, to minimize tool wear, hard materials have a comparatively lower value of optimal feed per tooth.

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You can either use the chip load formula or a chip load calculator to calculate the chip load value for your setup and then compare it with the optimal chip load value for a similar setup.

To further reduce the feed rate, you can use a cutting tool with a smaller diameter (such as 1/8″ 2-flute tool), which reduces the optimal chip load (to around 0.004″), thereby reducing the optimal feed rate (to around 64 ipm).

For example, when using a 1/2″ 3-flute cutting tool for machining 3/8″ softwood on a CNC machine operating at 10,000 RPM, you can calculate the optimal feed with the help of chip load.

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It can also be defined as the maximum load that a cutting tool such as router bits, can withstand without degrading the tool’s life.

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You can further reduce the optimal feed rate by reducing the RPM to 8,000, but it must be noted that reducing the RPM too low can degrade the quality of the cut.

Generally, soft materials shear off easily under the action of the cutting tool. Hence, they have a higher value of optimal chip load.

By the rule of thumb, the higher the spindle speed lower will be the chip load. This is because higher RPM results in a high inertial force, which thereby facilitates an easy chip removal.

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Therefore, it is important to ensure optimal chip load to produce high-quality machining results with maximum tool life.

Calculating the appropriate chip load helps reduce tool wear, improve surface finish, and increase the overall efficiency of the machining process.

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This load drastically affects the tool’s life, and if the load exceeds a certain limit, it can even lead to breaking the tool.

A beginner-level CNC machine cannot handle such high feed rates, and therefore these parameters need to be updated to match your machine’s capabilities.

So, the logical decision here is to maintain an extremely shallow depth of cut to reduce the resistance offered by the material.

Generally, most manufacturers provide an approximate value of optimal chip load in terms of the percentage of the tool diameter or a chip load table for their product. This approximate value provides a reference point and you can slightly vary the parameters during the test runs to find the best suitable setting for your application.

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The table below shows the optimal chip load for different materials and cutting tool diameters when the depth of cut is equal to the diameter of the tool.

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Although shallow cuts will eliminate the risk of snapping the tool, the rubbing action of the cutting edge against the workpiece can result in work-hardening of the cutting edge, and eventually losing its sharpness.

However, as the depth of cut increases, the chip load on the tool increases, and therefore the value of optimal chip load, for a particular feed, speed, and flute configuration, decreases.

However, the amount of material removal per revolution remains the same, provided the tool diameter and other machining parameters are similar.

Chip load during a machining process is primarily dependent upon factors such as speed, feed, and the number of flutes of the cutting tool.

First, use the table to find the optimal chip load corresponding to softwood and 1/2″ tool diameter, which is around 0.022″.

Thicker chips dissipate heat readily, thereby preventing overheating and minimizing the need for cutting fluid, whereas thin chips fail to do so.

The resistance offered by the material against the shearing action of the tool results in the development of load on the cutting edge.

However, it also depends upon other factors like depth of cut, type of material, machining capability of the CNC machine, etc.

Similarly, hard materials are difficult to machine, and increasing the chip thickness can result in tool wear, therefore hard materials have a lower value of optimal chip load.

This means that the higher the feed rate, the higher will be the chip load and therefore, the lower will be the quality of the cut.

Generally, it is recommended to maintain a low feed rate for finishing cuts, whereas high feed rates are used during roughing cuts.

Therefore, from the optimal chip load table, we can identify the optimal tool diameter (3/8″) for aluminum corresponding to 0.008″ chip load.

Generally, it is recommended that, for a depth of cut equal to twice the tool diameter, the optimal chip load should be decreased by around 25%.

This can be understood from the fact that a single flute cutting tool produces one chip per revolution, whereas a 3-flute cutting tool produces three chips per revolution.

As a result, the chip load is equally distributed among the flutes of the cutting tool, thereby reducing the chip load on individual flutes.

In this example, we can reduce the feed rate by replacing 3-flute with a 2-flute cutting tool and setting the chip load to minimum of the recommended value in the table, which is 0.021″.

However, as mentioned before, if the depth of cut is increased to around twice or thrice the tool diameter, the values in the table should be decreased by about 25% and 50%, respectively.

However, maintaining an extremely slow feed rate will increase the cycle time and also affect the tool life by increasing the dwell time.

Shallow depth of cut at high RPM can result in rubbing of the tool against the workpiece and generating a lot of heat to damage the workpiece and the tool.

According to the above equation, the chip load varies directly with the feed rate in inches per minute (IPM) and inversely with RPM and the number of flutes of the cutting tool.

No, the chip thickness is not necessarily equal to the depth of cut. For a cutting tool with multiple flutes, the number of chips produced per revolution is equal to the number of flutes, as a result, the chip thickness, for a particular depth of cut, decreases with an increase in the number of flutes.

This article will provide a detailed guide on chip load along with steps to calculate the optimal chip load for your operation.