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Keep the Pressure On H


igh-pressure coolant has been around for decades. Machine tool builders have long recognized its tremendous benefits, and most now offer through-the-tool coolant and high-pressure pump options on their machining centers and lathes. Cutting tool providers have likewise seen the light, and the majority of solid-carbide end mills and drills, slotting cutters, face and shell mills are now available with internal channels to bring cutting fluid where it’s needed most: into the work zone. Not only does this keep tools and workpieces cool, it lubricates cutting edges and improves tool life. What’s more, high-pressure (HP) coolant greatly aids with chip evacuation—anyone who’s ever cringed at the grizzly bear sound of metal being recut can attest to the importance of effective chip clearing. So why aren’t you doing it? Studies suggest that less than half of all machine shops utilize high-pressure coolant in their metalworking operations. For those shops with newer equipment, there’s simply no excuse, but even for those with- out the latest and greatest machine tools, retrofitting older equipment with through-the-tool coolant is a straightforward matter of bolting on an adapter block and buying coolant-capable toolholders. If management balks at the price tag of a high-pressure pump, consider this: HP cutting fluid creates a hydraulic wedge be- tween the chip and the cutting surface. This reduces crater wear and lowers cutting temperatures, extending tool life by 50% or more even in difficult-to-machine materials. And since HP breaks even long-chipping materials such as Inconel and titanium, there’s no more stopping the machine to extract dangerous bird’s nests of razor sharp chips, or adjust coolant nozzles. Best of all, cutting speed increases of 30% and higher are possible with HP, substantially reducing cycle times. Simply put, an HP cool- ant strategy means predictable processes, more metalcutting, and a smaller tooling budget. It’s time to get cool.


Using a less than perfect tool for any given operation might be an expedient choice, but most would agree that making a hole with a center cutting end mill is nowhere near as efficient as drilling one with an actual drill bit. Some of these bad habits evolved from the days of manual tool changers and 200 ipm (5080 mm/min) rapid traverse rates, when swapping out tools was a painfully slow process, but today there’s absolutely no reason to skimp on cutting efficiency to save a second or two on a tool change. And if you’re worried about the time needed to touch off a few extra cutters, thinking it’s easier to use what’s already in the carousel, then you’re not taking advantage of offline preset- ters and quick-change tooling. Shame on you.


Today there’s absolutely no reason to skimp on cutting efficiency to save a second or two on a tool change.


Some of this “get ’er done” mentality extends to car- bide as well. A low-volume job shop might get by with a general-purpose PVD-coated grade to cut Inconel one day and aluminum the next, but this less-than-optimal approach invariably leads to longer cycle times and poor tool life. For example, improvements in carbide molding and grinding techniques are producing unorthodox insert


shapes with a dozen or more cutting edges, promising to greatly reduce tooling costs. Coating chambers are getting smarter, as are their own-


ers, providing us with such innovations as unidirectional CVD to increase wear resistance, and edge-line secure PVD coatings that resist flaking and chipping. TiC and TiN have evolved to multiphase TiAlN, AlTiN, ZrN, TiAlCN, MT-TiCN, Al203, and a host of application specific grades able to tame even the toughest of materials. Carbide itself has improved as well. Grain sizes have become progressively smaller, going far beyond the now blasé micrograin carbides introduced decades ago. Cobalt rich, submicron substrates are now common, as are dual property “gradient” substrates that pair cubic carbonitrides for hot hardness at the cutting edge with tungsten carbide binders beneath, offering a best of both worlds solution to cracks and chip hammering. The message here is that cutting processes in any shop should be carefully analyzed. The right tool, the right geom- etry, the right grade and chipbreaker—perhaps perfection is out of reach, and in some cases unnecessary, but there’s no reason to settle for a solution that’s not at least darned good. With most cutting tool manufacturers boasting dozens of grades and literally hundreds of insert shapes, styles, and sizes, huddling with a knowledgeable application engineer for some fine-tuning can lead to big payoffs downstream.


May 2016 | AdvancedManufacturing.org 91


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