Cutting tool repair

10 May 2021

The decision to repair a tool is influenced by the type, use, substrate and coating of the tool. Other factors include: the value of the workpiece, the life of the tool, the complexity of the process, the processing site and the level of processing technology, etc.

Bit repair

Carbide bits are the most common repairable tool and the easiest to repair. When the bit is blunt, the drill tip can be repaired. If the bit has a chipped edge or is seriously damaged, the damaged drill tip can be removed before it is polished. As long as the beveled part of the bit is not excessively worn, it can usually be repaired by simple regrinding.

Compared to other tools, remediation has less impact on the bit diameter, making it ideal for remediation. Each repair controls the size differently. An ordinary bit may be repaired and reused five to six times before it is scrapped, whereas a bit used for machining high-precision holes may be repaired and reused only three times.

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End milling cutter repair

End-milling cutters are also best suited for restoration and reuse. The tricky problem with fixing end mills is that regrinding can affect their diameter. For example, if you send a 12.7mm end mill to be repaired, you may come back with a 0.51mm or 0.76mm smaller tool.
In order to ensure the quality of machining, it is necessary to adjust the offset of CNC machine tools. However, modern CNC machines with adjustable offset make it possible to use a repaired end milling cutter, and many CNC machines can set the offset automatically with the help of tool presetting equipment.

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Large and expensive tool repair

Larger or more expensive tools are also candidates for regrinding. In general, monolithic carbide end mills with diameters smaller than 12.7 mm do not have much regrinding value.
The most valuable repair is turbine blade root milling cutter, roughing end milling cutter, gear hob, expensive and almost all can be regrinding repair. Steam turbine blade root milling cutters have complex and precise geometries. Advances in CNC grinding technology have made it easier and easier to regrind such complex tools. Gear tool life can vary greatly, with some tools being able to process only 5 pieces before regrinding, while others can process tens of thousands of pieces.

Effect of coating on tool repair

Coating can determine whether a tool is worth repairing -- regrinding CVD diamond coated or diamond-like coated (DLC) tools is often not economical. For titanium - or chrome-based PVD-coated tools, tool repair is not an issue because all of the tool's functional cutting surfaces can be directly reground without first removing the coating.
In fact, it is easier to remove the AlCrN coating from the tool than the AlTiN or TiAlN coating. Chemicals used to remove the AlCrN coating do not cause any damage to the tool base material, especially the cemented carbide, whereas chemicals used to remove the TiAlN coating will erode the cemented carbide.

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Cost of repair tool

The price of the repair tool is much lower than the price of the new tool, but it is difficult to guarantee the consistency of its quality.
It is recommended that tools that are intended to be reused be repaired before they have chipped edges or severe wear, so that less tool material is removed during regrinding.

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