Speeds vs. Feeds

The terms speeds and feeds refer to the different velocities that are an integral part of the cutting process. Both are essential to the process and their combined effect is what allows the machine to effectively cut materials. The “speed” refers to the cutting speed and the “feed” refers to the feed rate. Many machines specify their cutting speed and feed rate, and often it can vary based on what is being cut. Many times the speed and feed rate will even be determined by the type of bit you are using to make the cut. Understanding the concepts of speed and feed will help you on many levels, whether you are buying a machine, operating the one you already own, or selecting tools to use.

Cutting Speed

The cutting speed is the velocity between the cutting tool and the surface of the material. This means that it is measuring the speed at which the edge of the cutting tool is passing the material. The cutting speed is often defined by the revolutions per minute or the spindle speed. However it can still be applied to a cutting tool that doesn’t rotate, such as the bit used in knife cutting. In this case it will just be defining how fast the cutting edge moves through the material.

Factors that should be taken into consideration:

• Type of material being used
• Type of tool and specifications
• The type of cut being made

Feed Rate

The feed rate is the speed at which the cutter advances through the material. It measures the rate at the tool progresses through the cutting job. For rotating bits or tools such as a spindle, feed rate is defined as the distance advanced per revolution. For non rotating tools such as in knife cutting, the feed rate is measured as inches per minute.

Factors that should be taken into consideration:

• Type of tool and specifications
• Type of material being used
• Desired surface finish for end product

Implications

Varying both speed and feed can have significant implications for your operations. Many people when starting out using their CNC machine the first few times think that slower may be better, however this is not the case. There are certain problems that can occur if the speed and feed are too slow. For example the feed rate is too slow and cutting speed is too fast, then rubbing of your tools and the material can occur which leads to decreased tool life. If your cutting speed is too slow and your feed rate is too fast, it can lead to tool breakage when combined with a high feed rate. These two examples demonstrate how important it is to understand your speeds and feeds. So make sure before you embark on a project or start cutting a job that you check your tool specifications carefully. If looking to purchase machinery or tooling, take these two rates into careful consideration, along with the type of material you need to cut. This will end up saving you the costs of broken tools and possibly wasted material. It will also ensure that your production runs smoothly and the end product is of high quality.