Cutting tool repair used to be something that just about any machine shop could do. Not anymore.

As indexable-insert tools grow more complex and tolerances get tighter, the machinery required to repair these tools is often the same equipment used to make them in the first place. As a result, it is more difficult for shops to repair their tools using manual equipment, as many have done in the past. Manual repair may lead to tools that look good but do not perform properly.

“Many companies have continued to scale down their internal machine shops, and the lack of skilled staff in these areas has made internal repair difficult,” said Julie Reiling, president of Carbide Tool Services Inc., Anoka, Minn., a tool repair company. “As a result, they need to select a repair source that can produce products using controlled and documented procedures. Incorrect repairs can lead to increased indexing time and increased tool change frequency, which increases cost—the opposite of what the shop had intended.”

While many cutting tool repair services have invested in CNC machines and automation equipment to repair sophisticated indexable tools to “as-new” condition, they still have to fight the perception that all tool repair is done manually—sometimes with poor results.

“Many small repair shops rely entirely on manual machining processes,” added Olaf Klutke, president of GKI Inc., Crystal Lake, Ill. At his company, while some tool repair is still performed manually, more work is being shifted to automated equipment “identical to that used to manufacture the tools in the first place,” he said.

Quality Matters

The key issue in tool repair is the cost of quality. CNC machines and testing equipment require a substantial capital investment, but companies that use the equipment say it is vital to efficiently repair more complicated indexable tools to as-new condition, according to Klutke.

If a machine shop has tried a manual repair service and not been satisfied with the results, it may just buy new tools. “This gives tool repair a bad name,” Klutke said. “[Many shops] have given up on tool repair due to substandard quality, and they are losing out on millions of dollars in potential savings as a result.”

Carl Lemke, president of tool repairer A.P. Engineering, Holly, Mich., agreed that tool repair’s image needs to be repaired. “Unfortunately, there are a number of bad ‘craftsmen’ out there who can make a tool look pretty, but the customer finds that tool can’t perform as needed,” he said.

However, tool repair operations that use state-of-the-art test and inspection equipment can extend the life of indexable tools. “Repairing cutting tools comes down to dollars and cents,” Lemke said. “On some specialty tools manufactured for certain processes, the savings of repair over purchasing a new tool can be up to 90 percent.” Often, there’s a time savings as well because the repair may take less time than producing and delivering a new tool, he added.

While a small percentage of tools with an insert pocket are damaged beyond repair, all others are candidates for repair, according to Klutke. “Customers often assume a tool is beyond repair and are shocked to find that it is not,” he said. An unrepairable tool would be one with a severe crack that runs the length of the tool, that has a bent bar or one that is severely warped, Klutke explained. Most indexable tools can be repaired and returned to spec two to five times or more, depending on the type of tool and how it is applied. Some shops routinely use three repair cycles as their standard, he said.

Major Improvements

Reiling of Carbide Tool Services noted that major improvements have been made in the equipment used by cutting tool manufacturers over the past decade.

“High-precision indexable tooling with modern shank technology make it critical that the repair operation has precise machining controls and, more importantly, good tool inspection,” she said. “There must also be controls in place to properly rebuild the tooling without disturbing or sacrificing the original integrity of the steel selected by the OEM. Altering the integrity of the original tool steel will compromise tool performance regardless of the tolerances held. Tool accuracy and steel integrity factors must be understood and controlled throughout the repair process.”

Indexable tool repair must achieve demanding tolerances, according to Dan Ryan, tool repair leader for NTM Inc., Fridley, Minn. “In light of tighter [part] tolerances, it is vital that the overall quality and the tolerances of repaired tools be as good or better than the parts being machined,” he said.

Regarding workpiece tolerances, “tooling accuracy is critical because the dimensional and geometric tolerances on workpieces gets more stringent as the machine tools get more sophisticated,” said Jim Leigh, co-owner, Pyramid Rebuild and Machine, Talmadge, Ohio, a rebuilder, retrofitter and remanufacturer of machine tools. “Today, it is commonplace in many shops to hold tolerances of several tenths in chipmaking operations. This level of precision was once solely the realm of grinders.

Success in tool repair typically depends upon two key variables: the workpiece quality requirements and the number of pieces the repaired tool must machine, according to Leigh. “Where either of these variables is high, machine shops should probably choose a specialist with sophisticated equipment to repair their indexable tooling,” he said.

Changing Tool Configurations

Changes in tool configurations are making tool repair even more of a potential cost savings issue. “There is a trend toward multifunctional combination tools that reduce cycle times and tool changes,” said Jerry Plummer, president of Specialty Tools Inc., Beloit, Wis., a solid-carbide toolmaker that also reconditions worn or dull solid-carbide tools. As an example, he cited a multiple-diameter plunge tool. Because combination tools are often specials and more costly to purchase new than standard, single-function tools, they offer an additional incentive for shops to have them repaired.

Like others interviewed for this article, Plummer said the skills of the machinist repairing a tool are as important as the equipment they use. “Tools must be repaired by qualified machinists who have access to adequate equipment and inspection. However, the driving factor is how complex the tool is and the number of tools being repaired to warrant doing the repair on a CNC machine,” Plummer said.

High-Speed Scrap?

Production volume, tool complexity, machinists’ skills and ‘art’ all play into the decision to either repair a tool manually or on a CNC machine. “Many high-volume parts are made on automated equipment,” Leigh said. “If tooling is faulty on this kind of system, you are simply making scrap at a high rate of speed. The more automated any process becomes, the more reliable each component of the process must be. Certainly tooling is one of those components. Indexable tooling that is not up to snuff will wear more quickly.”

At high production rates, substandard indexable tools will degrade more rapidly because of irregular or inconsistent chip load from one insert to the next. If tools are not running true because they were not repaired correctly, some of the inserts will cut a larger diameter than others, removing more material on each revolution than the others. “All of this will produce shorter insert life,” Leigh said. “In any operation but particularly in faster, automated parts production, this can chew up a lot of carbide quickly, not to mention the downtime required to troubleshoot the problem and change inserts. These problems can occur if any aspect of the toolholder’s geometry varies from one insert pocket to the next, such as rake angle or clearance angle.”

Organized Plan

Tool repair works best when it is organized and made part of shop policy, according to Reiling of Carbide Tool Services. This program includes tool collection, distribution and operator training. “We work with our customers to organize structured repair programs at their facilities that stress the value of reducing tooling costs by using repaired instead of new tools. This can dramatically reduce tooling inventory requirements, further reducing costs.”

For example, Carbide Tool Services has implemented an indexable tool repair program at a large aircraft manufacturer for drills, mills and toolholders. CTS established up-front pricing and stores the manufacturer’s damaged indexable tooling. The customer issues repair orders as the tools are needed, and CTS then repairs the toolholders to their original specifications. The manufacturer saves over $150,000 annually by repairing damaged indexable tools vs. buying new, according to CTS.

GKI’s Klutke agreed that parts manufacturers should create a comprehensive program to ensure that every repairable tool is repaired, thereby maximizing savings,” said GKI’s Klutke. “This begins with a tool collection policy throughout the plant. Often tools are disposed of in scrap bins, never being considered for repair.”

While the most important reason to repair tools is to save money, the most important factor to look for in a tool repair facility is quality, according to Klutke. A repaired indexable tool typically costs 50 to 85 percent less than a new one, but if the repaired tool does not perform as well as a new tool, those savings are negated. “In fact, a repaired tool could end up costing more than a new tool if the repaired tool fails prematurely or if it was not repaired to the correct dimensions and tolerances,” Klutke said. GKI guarantees that its repaired tools will perform the same as new tools and that life expectancy will not be affected.

While tool repair can be cost effective, NTM’s Ryan cautioned against potential users of tool repair services not doing their homework. Many tool repair facilities have opened in recent years and “it is always buyer beware. Not all repair outfits do justice to the word ‘repair.’ ”

The Age of Lean

Global competition and lean manufacturing are two drivers of tool repair. Years ago, it was more common for shops to scrap worn tooling, said Arthur Ellis, tooling engineering technician, Brewer (Maine) Automotive Components Inc. “We save perhaps 50 percent on repair vs. buying a new tool. I stick with the repair company’s recommendation of three times for rebuilding tools.”

His advice for others looking to move towards more repair and less scrap is simple: “Set up a program. Use trial tools with the suppliers you check. Make sure your tool drawings are correct and up to date.”

GKI’s Klutke noted that tool repair begins with a plantwide tool collection policy. “Tool repair firms offer various services to facilitate the repair process,” he said. “For example, our company offers collection bins, shipping containers and off-site tool inventory management.” He added that shops considering a tool repair program should visit the repair facility they intend to use.

Depending on the type of complexity of the tool, the tool repair service may need the tool prints, and the repairer should be able to provide a certificate of inspection with the repaired tool, said Specialty Tool’s Plummer. That requires appropriate inspection equipment and fixturing setups as well as machinists with knowledge of the growing variety of indexable tools on the market.

A repair shop should also be ISO certified and have precise quality controls, including documentation and inspection procedures, said Carbide Tool Services’ Reiling. “A quality repair facility needs precision equipment, OEM fixturing and skilled labor. Understanding the tolerance requirements and maintaining the integrity of the material is absolutely crucial to the repair process,” she said.

Reiling noted that inspection is particularly important for some applications. For example, one U.S. automotive manufacturer uses special indexable toolholders to manufacture certain parts. The imported toolholders are expensive, held to tight tolerances and new orders require extensive lead times. Carbide Tool Services developed a repair program for these toolholders that now saves the customer more than $200,000 annually. Under the program, CTS houses master prints and inserts for inspection to ensure quality, and its inspection process mirrors the receiving inspection procedure of the customer. To reduce delivery time, the customer issues a blanket order so that repair can begin as soon as the tools arrive at CTS.

All tool repair services are not created equal. Even if your shop has had a bad experience in the past with tool repair, it may make sense to take another look at how tool repair is done today—including a site visit to your potential supplier. Costly indexable tools are too valuable to entrust to just anyone.