How to stop breaking end mills

Tired of breaking end mills?

Machine shops, production plants, home workshops, and a variety of other End Mill users know how frustrating it is to have an End Mill break in the middle of a machining job. Machinists working with CNC machines, lathes, mills, and other production equipment can’t afford to lose productivity due to a tool failure, The costs in terms of manpower hours, machine downtime, workpiece damage, and other considerations add up to a lot more expense than just the cost of a new End Mill.

Top 5 causes for breaking end mills

There are several reasons for tool breakage. Proper diagnostics determining the causes for breaking End Mills should be conducted to reduce breakage in the future. Some of the most common reasons for breaking are:

1 | Stress

End Mill design and engineering involves a combination of dimensions, thicknesses, and material composition. Stress can occur as a result of a machine operator being unfamiliar with an End Mill tool’s characteristics and how it performs due to its design, construction, or application. A CNC machine can apply more stress to an End Mill tool than it is designed to work with by pressing into a workpiece with greater force than it can handle at speed.

2 | Temperature

Many machine operations occur in rapid succession, causing the End Mill head to heat up beyond its operating range. The additional heat expands the metal and decreases its strength. Tiny cracks can appear which weaken the structure of the End Mill eventually causing a breakdown. Stress fractures affect tool dimensions and can result in improper dimensional cuts in tight-spec conditions.

3 | Head design

End Mills come with 2-flute, 3-flute, 4-flute, and 6-flute cutting heads. Each design is specific toward accomplishing a task more efficiently and productively. The more flutes on the End Mill head, the faster the cuttings are removed from the contact area creating cleaner, more precise edges. Use of the improper head design can result in repeated failure as well as damaged workpieces that will have to be scrapped.

4 | End mill material

Each manufacturer blends different metals in the construction of their tools. It is preferable to have high-carbide steel with other alloys like Cobalt incorporated to increase strength and durability. Manufacturers that use inferior grade steels or weaker alloys will produce End Mills that will fail more often than those manufacturers that use a proper mix of alloys. US-made tools tend to have better performance characteristics than off-shore sourced tools due to higher levels of important metal ingredients in their steel.

5 | Work piece material

Depending upon the type of material the workpiece contains, the cutting head of an End Mill has to be engineered to perform the task required in the material being worked. Special End Mills are available for use on aluminum materials as well as other designs for plastic, nylon, and other non-metallic materials. Matching the cutting head material to the workpiece material properly insures greater tool performance and longevity.

Know your end mill

Professional machine operators need to understand the design, engineering, application, and specifications for the End Mills and other tools they use. High-capacity production floors and mom-and-pop machine shops alike both demand the same level of productivity, longevity, and value from their tools and a complete understanding of a tool’s capabilities and applications goes a long way toward avoiding disasters, saving time, saving money, and achieving success.

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