CNC machining of tool steels is very common nowadays in the tool and die industry especially in the automotive and commercial industrial applications. CNC machining is the preferred method for the manufacture of medium to high volume production parts. However, tool steels such as D-2 and A-2 materials can sometimes pose problems of chatter during CNC machining especially for parts with a high aspect ratio. By aspect ratio, we mean the ratio of the length of the part to the diameter. When parts with high aspect ratios are to be machined using CNC machining methods, chatter is likely and this chatter can cause several problems and need to be minimized or eliminated as outlined below.

Chatter during CNC machining of tool steel hardware can cause a lot of problems. The first problem is the premature wear and damage of the cutting tool inserts. Secondly, dimensional accuracy control gets affected. Surface finish of the component machined will significantly suffer. Additionally, excessive noise during machining gets generated which obviously is the least of the culprits. Hence control of chatter is a priority during CNC machining of tool steel components. Additionally, since the cutting inserts need to be changed often because of premature wear, extensive down time is exhibited which leads to lowered production rates. The first step in eliminating chatter is to address feeds and speeds parameters. The spindle speed should be cut down. Next the depth of cut should be increased marginally. Feed rate or the inches feed per revolution parameter could be left unchanged from those values used for lower aspect ratio components. Next, use inserts with the sharpest possible geometry. For example, if you generally use a DNMG432 insert, change it to a DNMG431 insert. Inserts should be of the highest quality. Stay away from using uncoated inserts. The coolant used should be fairly fresh. You do not need to drain and replenish the entire coolant tank. However, at least add some fresh coolant mix to the coolant tank, unless the current coolant is completely spent. Proper coolant plays a big role in prevention of premature wear of cutting inserts and therefore in maintaining good surface finish. Finally, hold the piece as close as possible to the chuck without hitting chuck barriers. This last step is very critical, since you need to machine as close as possible without crashing the turret. Hence review the CNC program several times to ensure proper tool path control and chuck barrier data has been set. CNC programming techniques should also be visited to enable turning in sections rather than turning the entire length of the piece in each machining pass. Following all of the above procedures can minimize or eliminate chatter during CNC machining of tool steel components.

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