The fix is in: Inspection Efficiency

Indexable-insert tool repair can require a lot more than a manual machine. CNC machines and inspection equipment are often needed to effectively refurbish tools.

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.”

Courtesy of Carbide Tool Services

The quality department at Carbide Tool Services uses Parlec presetters and other inspection equipment to verify tool dimensions 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.”

Courtesy of GKI

Before and after repair samples of common indexable tools: lathe tools, drills and mills.