One of the great benefits of solid round cutting tools is the ability to resharpen them after heavy use. Done right it’s like having a cat with nine lives: Dull…then like new. Dull again…and like new again. And since the cost to recondition solid tools is generally lower than the cost to replace them, there’s an economic benefit. The question then becomes what’s the best way to achieve the greatest possible benefit?
The easiest option for reconditioning cutting tools is sending them to an outside regrind shop. A number of companies specialize in reconditioning tools and an even greater number both manufacture and regrind solid round tools. You might even find a local firm that offers regular pick-up and delivery service, with the obvious benefits of fast turnaround time and the ability to readily consult with the team refurbishing your tools.
At the other end of the spectrum are big, centralized firms and none is bigger than US Tool Group (Farmington, MO). As you might expect, a large centralized firm has the advantage of being able to assign teams to specific tasks, like QC or grinding a particular type of tool. And that leads to higher levels of expertise and efficiency. As Bruce Williams, US Tool’s president, put it, “We process half a million tools per week so we can have operators that specialize in nothing but endmills, or counterbore tools, or high-performance drills… and they get really good at it.” Williams added that their high volumes also enable them to amortize setup costs over more tools, lowering cost per tool.
US Tool’s size also supports an in-house development team and machine shop that designs and builds its own equipment. A key example (and Williams’ own brainchild) is an automated drill sorting machine that picks tools from an unsorted pile, removes build-up and burrs on the shank and tip, and puts them onto a conveyor that carries them under two lasers.
“The lasers take a detailed profile of the drill. Software then performs a feature recognition routine based on diameter, back taper, number of margins, helix angle, flute length, overall length, and type of adapter,” explained Williams. “It compares this to a database of the drills used by the customer and matches it to a particular material code for that specific customer. A robotic arm then deposits the drill into any one of 300 bins. The machine cycles every 3.5 seconds.”
From there the drills are pointed and split, inspected, packaged, and shipped. Thanks to this automation, a customer can send US Tool thousands of drills in varying styles and sizes—having spent no time sorting them—and get them back sorted, labeled, and in like-new condition in three weeks.
The automation just cited covers standard twist drills and US Tool is close to fielding a solution that will also speed the processing of high-performance drills. But for US Tool or anyone else trying to identify and then recondition more complex geometries, there’s no escaping the need for a human expert. In some cases, it’s also important to work closely with the cutting tool OEM to really understand what’s required. US Tool maintains such relationships with a number of the OEMs and Williams argued that their large size and team of specialists gives them the ability to handle anything that comes in the door.
At the same time, virtually all the OEMs recondition their own tools. Some, like Kennametal and Komet, also license outside regrinders to do so. There’s a case to be made for sending tools back to the manufacturer, particularly if they have specialized coatings. Eaven Sims, manufacturing supervisor at Emuge USA (West Boylston, MA) is one such proponent. Sims explained that although top inspection equipment makes it possible to come very close to reverse engineering a tool’s geometry, coatings are another matter.
“Unless it’s something basic like TiN, the OEMs use different names for their coatings and trying to mimic it can be hit or miss,” he said. “We come close. But even if you can identify it as a TiN TiAlN multilayer, there are three or four manufacturers that apply it differently and with different thicknesses, so you’re never 100% sure. Whereas when we recondition our own tools we know exactly what the coating was and how to apply it.”
Sims added that it’s important to clean the tool properly before re-coating to ensure good adherence and that adding about 3 µm per coating layer to the unground surfaces on the tool will not be a significant change in size for most applications. On the other hand, it’s difficult if not impossible to re-coat a molybdenum based “non-stick” coating no matter what you do. And diamond coated tools present a serious challenge to regrind, so it’s often not economically viable to do so.
Edge prep has emerged as another important “secret sauce” for high performance tools, and since it’s difficult to measure and duplicate edge prep, it’s another factor to consider in sourcing your reconditioning. As Sims put it, controlling hone sizes and geometries has “become the new frontier in the industry. We’re very protective of that here and I’m sure other manufacturers are as well.” Emuge even has their own proprietary honing equipment, one type specialized for drills and another for endmills.
Emuge also regrinds taps, albeit only their own complex taps. Sims explained that larger diameter Emuge taps are relatively costly, making them a good target for regrinding. But when “end users have tried regrinding [these taps] themselves or getting regrinds from other vendors it is not done correctly. We know the geometry, the edge prep, the coatings, and so forth. For example, grinding the flute face requires a particular form wheel. If you don’t know the wheel form you will change the rake angle in the flute, which will impact the tool’s performance dramatically. There’s also a special relief on the chamfer to help guide the tap. I’ve never seen a re-grinder even try to do that, but we do.”
Sometimes even the original manufacturer can’t efficiently regrind the tool. Emuge’s own circle segment endmills are one example. “It is such a difficult tool to make that we’re finding the cost to regrind is almost as much as a new tool,” said Sims. “Not to mention the fact that it’s a proprietary form that can only be applied correctly using sophisticated CAM software. Since regrinding it would create a slightly smaller diameter and other small changes, the user would have to enter a new profile into the CAM system. But once this program is well established we will be regrinding some of these tools.”
We said at the outset that the cost to recondition tools is generally lower than the replacement cost. In fact, Williams and others say the cost to regrind is typically about half the cost of a new tool. When you consider that an endmill can be reground three times, on average, the numbers become even more compelling.
Take the example of a $50 endmill that can be reground for $25. Buying the tool and using it four times (with three regrinds) would cost $125 versus buying four new endmills at $200. That’s a 38% reduction in tooling costs, or 4 tools for the price of 2 1/2. The cost to recondition more expensive tools can often be a smaller fraction. Guy Suchecki, vice president and director of manufacturing at Accurate Regrind (Grand Rapids, MI) pointed to a Titex drill that costs over $400, yet can be sharpened and recoated for $29, a savings of over 90%.
But reconditioning also makes sense if the numbers are at the other extreme. Putting aside the rare cases where the regrind can cost more than the new tool, Williams said some customers question the wisdom of regrinding a tool at 90% of the cost of the new tool. “I ask them if they’d buy the new tool for 10% less and of course they answer ‘yes.’ That’s what you get with the regrind, so why not do it? Plus it’s the environmentally better thing to do.”
Note that Williams said the regrind was effectively a “new tool.” That’s because US Tool, Accurate Regrind, Better Edge (Scottdale, PA), and others say their reconditioned tools will indeed perform as well as the new tool. They’ll go a step beyond and say that if you consult with them on your particular application they can recondition the tool to perform better than the new tool.
“The OEMs do a phenomenal job of designing new tools,” Williams said. “But they typically develop them for a range of applications to meet the demands of a number of customers. We can tweak these tools to suit the needs of a specific application. The OEMs can do that too on the regrind, but not on the new product.
“The only wrinkle in whether a properly reground tool can perform as well as a new tool is if the tool had been abused in such a way that it affected the metallurgy, and we inspect for that,” he continued. “If a tool comes in with burn marks showing it’s been overheated, we scrap it. Our job isn’t to return every tool, it’s to return every tool that will perform as well as a new tool. If a customer has a good program in which they remove a tool before smoke starts coming out the cut, they will get a lot more life out of the tool.”
Williams added that while you can literally just throw your unsorted tools into a box, it’s always best to protect carbide tools by wax dipping them or putting them into tubes before shipping.”
Finally, US Tool offers another clever way to save money: “Dull inventory.” In this approach, US Tool takes in your tools, cleans them, and identifies them, but doesn’t refurbish them. Instead they list them on a secure server only you can access, from which you can “shop” for the tools you want reground. Williams added that from an accounting perspective it’s storing inventory in the least cost position. Plus you get reports listing tools which had no activity, suggesting it might be better to recycle the carbide.
If you’re a big tool consumer who’s sold on the economics of reconditioning, you might consider doing it yourself. After all, if the re-grinders are making money there must be a margin you can recoup by doing it yourself. But it’s a big step, not least because you can easily spend $250,000 on a CNC tool grinder. Plus there’s the cost of grinding wheels, workholding, coolant, utilities, floor space, and of course, the operator.
Today’s CNC tool grinders are easier to use than ever, but tools are also more complex than ever. What’s more, it’s probably fair to say that regrinding requires more skill than manufacturing. In any case, it’s definitely a niche field, so finding and keeping qualified operators can be a challenge. Then there’s inspection equipment. A CNC tool measuring machine will easily be six figures as well. Edge prep equipment is not cheap. Coating systems are another ball game entirely, such that even some major tool manufacturers sub-contract that service.
If your motivation is simply to save money on cutting tools, your annual expenditures for solid round tools should at least exceed the cost of the tool grinder, according to Markus Stolmar, vice president for tool grinding and measuring for United Grinding (Miamisburg, OH). But for some companies, the primary motivation isn’t the cost of tools per se, but the loss to production if the right tool isn’t available at the right time.
As the tool grind supervisor for a Tier 1 automotive supplier put it, “For us the added value for in-house support is reaction time, especially when there are issues. We are here anytime the lines are running. Seven days per week if needed. It’s hard to get that kind of commitment from an outside source.”He also pointed out that the time delay inherent to outsourcing the regrinds means you need more tools to cover the flow. But again, the main benefit is the ability to absolutely ensure the main production runs smoothly, because an outage there runs into hundreds of thousands of dollars per hour.
While Williams insisted that “production regrinding” should be turned over to an expert, he agreed that many manufacturers should have an emergency grind shop within their plant or readily available in the community to “address immediate needs, like adding a chamfer, or changing a radius.”
If you’re leaning toward building your own refurbishing operation, rest assured that the makers of CNC tool grinders and measuring machines have pushed each other to deliver truly remarkable technology. For example, auto-probing capabilities have “grown dramatically over the last few years” as Stolmar explained. “The more complex the tool the more you need to orient many details in order to effectively regrind it.” Of the 79 operations in the tool grinding software of United Grinding’s Walter brand, 21 are dedicated to probing.
The major players have also introduced various systems that automate regrinding mixed batches of tools. For example, an updated U-Grind machine from Strausak (Mundelein, IL) uses a modified pick-up gripper and cost-effective clamping sleeves for different shank-diameter tools. Walter and ANCA (Wixom, MI) have introduced RFID tags into similar systems to further enhance automation.
ANCA’s co-founder and co-director, Pat Boland, said the information required to resharpen the tool is recorded on the RFID tag at a central programming station, then affixed to the sleeve that carries the tool.
“When the machine picks up the tool it reads the RFID tag and automatically calls up the grinding program, the appropriate collet diameter, and the right wheels to produce the part. We have customers that classify the tools during the day, creating the RFIDs, then regrind unmanned at night.”
Boland also pointed to internal laser measuring systems that are so accurate “we’ve been successful regrinding drills down to 0.2 mm in diameter. I don’t know how commercially practical it is, but we can do it.”
Use a lot of two-flute drills? It may make sense to re-sharpen them yourself. Darex (Ashland, OR) offers several economical bench-top sharpening systems, including a four-axis CNC drill grinder for as little as $33,000. Although these systems can’t handle gundrills or twist drills with three or more flutes, the higher end models can handle high-performance carbide drill geometries fully automatically (except for loading and unloading the drills).
Darex has over 45 years of drill sharpening experience and they typically provide canned programs for any high-tech drills you need after reverse engineering your tools. Cycle times average under a minute. So, as Darex puts it, “For the price of a couple hundred premium carbide drills, you can sharpen in-house for only pennies a drill.” These machines are a definitely worth a look.
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