Wheel formed from abrasive material mixed in a suitable matrix. Takes a variety of shapes but falls into two basic categories: one that cuts on its periphery, as in reciprocating grinding, and one that cuts on its side or face, as in tool and cutter grinding.

The development of the tool began with a missed opportunity. When a long-time automotive OEM customer informed West Ohio Tool that it wanted to change from solid-carbide to PCD-edged tools for drilling holes in die cast aluminum transmission cases, some West Ohio Tool team members were skeptical. They understood the impetus: As good as carbide tools are, they still require regrinding after 20,000 to 25,000 holes, and after about 10 regrinds, they become too short to use.

With the solid-PCD tool project in mind, West Ohio Tool invested in the Walter Helitronic Power Diamond with both grinding and EDMing capabilities. With copper rotary erosion/electrode wheels, the machine EDMs the PCD portions of tools, then conventionally grinds any carbide areas.

“Whether formed from high-speed steel, cobalt, or tungsten carbide, uncoated tools can be used on non-ferrous and ferrous materials,” said Harvey Patterson, product development engineer at Scientific Cutting Tools Inc. “That being said, they typically work better on non-ferrous materials that create less heat and pressure, both of which deteriorate the cutting edge during the cutting process. The cutting edge pressure is dictated by the strength of the material being machined.”

Kerry Buchenroth, owner and founder of West Ohio Tool, acknowledged that using the right formulation of PCD was important – but not most important – in the drill’s development. “The real trick was not so much the material,” he said, “but instead figuring out how to braze the PCD onto the carbide, how to optimize the tool geometry and other such issues.” He credits his team and the shop’s high-precision CNC combination tool grinding/eroding technology as the key to overcoming the new drill’s development challenges.

“Another reason to use uncoated inserts is to avoid putting too much cutting pressure on thin-walled parts. With thin-walled parts, too much pressure can cause them to cave in or move. In these applications, you want to use an uncoated insert with a real sharp edge.”

When the customer went to another tool supplier, Buchenroth realized it was time to hone its expertise in PCD tooling and make sure the shop had the advanced technology on hand to work efficiently with both solid carbide and PCD. In addition to acquiring two high-precision wire EDMs, the shop now has seven Walter 5-axis grinders, an Ewag PCD grinder, a Studer S31 and two Helicheck CNC inspection and measurement systems, as well as a Helicheck Pro fully automated measuring system – all from United Grinding.

“The challenge with the outboard tip is that the outside PCD edges hold up great but the center of the chisel is still carbide, and it still eventually breaks down,” Buchenroth explained. “The goal for the new tool was to find a way to get solid PCD all the way across the center and effectively marry it to a carbide tool shank.”

“The heat can be reduced by using coolant. Coolant can be easy to apply if machining the outside of a part. When machining an inside, such as when boring or drilling, getting coolant directed to the tool to keep it cool can be more difficult, and coolant-through tools may be needed.”

Available in two major types: tungsten high-speed steels (designated by letter T having tungsten as the principal alloying element) and molybdenum high-speed steels (designated by letter M having molybdenum as the principal alloying element). The type T high-speed steels containing cobalt have higher wear resistance and greater red (hot) hardness, withstanding cutting temperature up to 1,100º F (590º C). The type T steels are used to fabricate metalcutting tools (milling cutters, drills, reamers and taps), woodworking tools, various types of punches and dies, ball and roller bearings. The type M steels are used for cutting tools and various types of dies.

A lower cutting speed that produces less heat helps reduce the risk of built-up edge that eventually breaks off and takes a part of the tool with it. Photo courtesy of Scientific Cutting Tools Inc.

It took six years of experimentation and trial and error along with tool grinding know-how for West Ohio Tool Co., a specialty cutting tool shop in Russells Point, Ohio, to develop its own commercially available cutting tool. The revolutionary tool is a solid PCD drill that generates from 800,000 to 1,000,000 holes in die cast aluminum without regrind or re-tipping required. That durability means a lot less downtime for today’s manufacturers, and it’s why the shop guarantees this tool will provide a lower cost per hole drilled than any other tool.

“A positive rake cuts with less pressure than a neutral or negative rake,” he said. “Think of whittling wood. If the knife blade is at 90 degrees to the wood, it is hard to cut; if the blade is at a slight angle, the cut becomes much easier.”

“Uncoated carbide is used a lot in the mouldmaking industry because the moulds are usually one-offs. They are high-value parts, some produced from difficult materials like titanium, and may be worth $20,000 before machining begins. The finished product has to be perfect.”

The EdgeX4 has another advantage, Buchenroth noted. Along with being extraordinarily slow to wear, the tool is relatively quickly made to order. The company’s expertise and advanced Walter cutter grinding machine technology enables West Ohio Tool to provide the new drill within a four to six-week delivery time – about four times faster than average for other specialty PCD tools – to help its customers get the “edge” on the competition.

Magee said, “Some new coatings can have 26 layers and keep a sharp edge. These are good for production parts that typically won’t be as tight a tolerance as a mould and die. In practical use, manufacturers producing very difficult parts will choose a sharp, uncoated insert because it can hold the size and tolerance that are needed.

Image

Sharp, uncoated inserts like the VK2 from Vargus are designed for processing non-ferrous material, aluminum, high-temperature materials, and titanium alloys. Photo courtesy of Vargus USA.

Image

“Everyone wants to cut faster and quicker, but I don’t know that it is better when you need perfection. There is still a place in manufacturing for uncoated, highly polished, fully ground inserts.”

Using inferior PCD leads to a breakdown similar to what eventually happens with outboard tips on carbide – outer cutting edges would be fine, but the center eventually fails or the PCD is too brittle to hold up to aggressive machining. Buchenroth likened the phenomenon to the children’s game of crack the whip.

This was also about the time that the shop invested in its fully automated Helicheck Pro measuring machine that can handle tools with a diameter range from 1 to 150 mm in the macro area, a machining length up to 330 mm and a tool weight of up to 25 kg. The CNC-based system is well-suited for fully automatic measurement of complex tool geometries such as with the new PCD drill.

Easily access valuable industry resources now with full access to the digital edition of Canadian Fabricating & Welding.

“In a production shop, a coated insert that will last for the predicted wear is needed, but when you are making a one-off part that takes a lot of skill, you need to be able to project what the tool is going to do every time you put it in the machine. No room for error.

These continuous improvements make it possible to identify a coated insert for almost any application.

Sue Roberts, associate editor, contributes to both Canadian Metalworking and Canadian Fabricating & Welding. A metalworking industry veteran, she has contributed to marketing communications efforts and written B2B articles for the metal forming and fabricating, agriculture, food, financial, and regional tourism industries.

Image

Boring or drilling with uncoated inserts may create enough heat that coolant-through tools should be considered. Photo courtesy of Scientific Cutting Tools Inc.

OSG’s master class of advanced performance tooling solutions for drilling, milling and threading. Unsurpassed performance for an extensive range of materials and applications. Quality, reliability and satisfaction. Bring your A Game with OSG’s A-BRAND®.

Reducing that pressure, according to Patterson, is best accomplished by using tools with a positive rake. How positive depends on the material. For example, cutting aluminum will require a very high positive rake; for HRSA or titanium, the rake doesn’t need to be as high as long as the edge remains sharp to avoid placing too much pressure on the part.

Some applications or materials, however, or even the desire to increase speed for faster material removal, can generate enough heat that the use of coolants should be considered.

Buchenroth knew that to develop and produce such a cost-effective, durable solid PCD tool, they would need an even more efficient solution for working with PCD materials.

Inserts sans coatings, however, still have their place.An unadorned insert with no coatings that could dull its cutting edge is often the choice when a manufacturer is faced with producing a component that has little to no room for variance from specifications from tough materials like cast iron, high-temperature materials, and heat-resistant superalloys (HRSA).

A highly polished, uncoated insert like the VK2P from Vargus can produce high-quality surface finishes in aluminum. Photo courtesy of Vargus USA.

The fully automated Helitronic Power Diamond provides complete machining in single clamping cycles. It changes from grinding to eroding, or vice versa, on-the-fly and automatically. In addition to PCD and carbide, the machine processes tools from HSS, cermet and ceramics in diameters from 3 to 320 mm, lengths up to 350 mm and weights as heavy as 50 kg.

A constant stream of advanced insert coatings flows from tooling manufacturers to offer increased tool life, better surface finish, characteristics to effectively cut a variety of materials, or custom layers engineered to provide ideal material removal for a very specific material or application.

The initial formulations of PCD the shop tried eventually crumbled and broke at the drill center while the outer edges were fine. This is when the shop realized that only the highest concentration of PCD would work for the new tool, so West Ohio Tool spent a total of six years of trial and error, working with different PCD materials as well as developing a proprietary brazing process to marry the PCD to carbide and tweak the tool’s geometry.

Machining operation in which material is removed from the workpiece by a powered abrasive wheel, stone, belt, paste, sheet, compound, slurry, etc. Takes various forms: surface grinding (creates flat and/or squared surfaces); cylindrical grinding (for external cylindrical and tapered shapes, fillets, undercuts, etc.); centerless grinding; chamfering; thread and form grinding; tool and cutter grinding; offhand grinding; lapping and polishing (grinding with extremely fine grits to create ultrasmooth surfaces); honing; and disc grinding.

Superhard PCD is difficult to grind, and the diamond grinding wheels used to do so wear out quickly – every amount of PCD material removed from the workpiece equates to the same amount of PCD that’s worn away from the grinding wheel. This makes grinding PCD an expensive endeavor. However, because PCD contains cobalt, it conducts electricity and therefore is well-suited for EDMing.

Customers have whole-heartedly embraced these outboard-tipped drills, including the automotive OEM customer whose PCD tool business they’d lost earlier. However, that same OEM was fighting the industry-wide battle for faster throughput and lower total cost of production and insisted on more. According to Buchenroth, the customer said drilling 350,000 holes without interruption was good but asked if we could make it even better in terms of output, so the West Ohio Tool team got to work.

Among the shop’s most recent grinders also from United Grinding are a Walter Helitronic and Walter Helitronic  Power Diamond, a two-in-one system that performs both grinding and EDMing. The shop complements its machines with Walter Tool Studio software for faster, easier programming.

“It’s about cobalt and tungsten carbide and a few other additives—how much a manufacturer puts into what I call pressed dirt. Then it’s about the finish and polish.” Uncoated inserts may lack extra layers of coating, but they are ground to accept a special polish, in some cases to a mirror finish.

Cutting tool material consisting of natural or synthetic diamond crystals bonded together under high pressure at elevated temperatures. PCD is available as a tip brazed to a carbide insert carrier. Used for machining nonferrous alloys and nonmetallic materials at high cutting speeds.

Substrate for uncoated inserts, Magee said, should be ultra-fine or nano-fine with a grain that is less than 1 µ. “Probably, there should be a 3 per cent cobalt binder to keep the very sharp edge. Fewer voids between the grains where the cobalt or another binder can melt keep the edge sharp.

Patterson said, “Pressure on the cutting edge combined with heat from friction caused by the material flowing across the surface of the tool can cause built-up edge. This buildup will eventually break off taking part of the tool with it which leads to tool failure.

Joe Magee, product manager for gear milling at Vargus USA, said, “Uncoated inserts are good for finishing, projects where you don’t want to put any stress into the part, and avoiding work hardening in the materials. If you cut high-temperature materials too hot or too fast, they will work-harden and cause trouble down the road.

Powers a grinding wheel or other abrasive tool for the purpose of removing metal and finishing workpieces to close tolerances. Provides smooth, square, parallel and accurate workpiece surfaces. When ultrasmooth surfaces and finishes on the order of microns are required, lapping and honing machines (precision grinders that run abrasives with extremely fine, uniform grits) are used. In its “finishing” role, the grinder is perhaps the most widely used machine tool. Various styles are available: bench and pedestal grinders for sharpening lathe bits and drills; surface grinders for producing square, parallel, smooth and accurate parts; cylindrical and centerless grinders; center-hole grinders; form grinders; facemill and endmill grinders; gear-cutting grinders; jig grinders; abrasive belt (backstand, swing-frame, belt-roll) grinders; tool and cutter grinders for sharpening and resharpening cutting tools; carbide grinders; hand-held die grinders; and abrasive cutoff saws.

Substance used for grinding, honing, lapping, superfinishing and polishing. Examples include garnet, emery, corundum, silicon carbide, cubic boron nitride and diamond in various grit sizes.

Main body of a tool; the portion of a drill or similar end-held tool that fits into a collet, chuck or similar mounting device.

“In the old game of ‘crack the whip,’ the child at the center basically rotates around very, very slowly in one spot while the person at the tip of the human whip is sent flying around. PCD is great at the ‘flying around’ part, as it cuts away at material at the edge of the tool,” Buchenroth said, “but at the center of the drill, where there’s zero surface footage, it doesn’t react well to being under that kind of pressure.”

According to Buchenroth, the Tool Studio software on the Walter machines significantly helped to speed up the trial and error process. The Windows-based software, which Walter developed with input from the team at West Ohio Tool, allowed the shop to simply fill in the required information fields for the latest iteration and run the job. The software’s 3D simulation capabilities provided visualization of both the grinding and EDMing processes and allowed the shop to make adjustments as needed before any material was actually removed.

This is the tool grinding technology that first helped West Ohio Tool to develop an interim PCD tool – a specialty PCD outboard tipped drill, capable of drilling 350,000 holes in die cast aluminum without the need for regrind or re-tip of PCD.

“Each regrind costs money and means downtime,” Buchenroth said. “PCD offered the possibility to minimize all of that, but it’s expensive and notoriously hard to work with.”

The aerospace industry, shops producing plastic moulds and dies, and applications that require tight tolerances, like ± 0.0005, and fine surface finishes are preserving the niche for uncoated inserts among their coated counterparts.

Since heat generation is reduced by the lower cutting speed, uncoated inserts can be run dry for most applications, which offers some advantages. “If you are finishing a part with a very tight tolerance, you get a better result cutting it dry. Cutting slow with an uncoated insert gives you controlled insert wear,” said Magee. “With the slow surface feed or speed you really don’t need to use coolant.”

After a total of six years of continuous testing, the tool was ready. Released in 2019 and called the EdgeX4, the patent-pending PCD tool drills from 800,000 to 1,000,000 holes in die cast aluminum thanks to a significantly stronger, faster, longer and more efficient design than competing tools. Although aluminum transmission cases for the auto industry were its earliest workpieces, the EdgeX4 continues to prove a boon to the aerospace industry as well, as it is able to drill through highly abrasive carbon fiber reinforced polymer materials with minimal wear as it does with aluminum.

Easily access valuable industry resources now with full access to the digital edition of Canadian Metalworking.

Keep up to date with the latest news, events, and technology for all things metal from our pair of monthly magazines written specifically for Canadian manufacturers!

Cutting tool materials based on aluminum oxide and silicon nitride. Ceramic tools can withstand higher cutting speeds than cemented carbide tools when machining hardened steels, cast irons and high-temperature alloys.

In addition to their very sharp edges, uncoated inserts contribute to needed perfection by slowing down the production process. A slower surface feed provides more control, and lighter cuts can be taken with the sharp cutting edge.

“The whole idea is to keep the sharp edge as long as possible,” said Magee. “For example, aluminum is very abrasive and it will wear off an insert corner when the process is run at high RPMs or high surface feeds. But if you can keep the sharp edge, you can continue the cut and keep a good tolerance.

Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.

Crucial to the drill development process was working with different formulations of the PCD material. PCD is measured by grain sizes that range from nanometers to hundreds of micrometers, usually referred to as nanocrystalline and microcrystalline. Smaller particles in higher concentration provide higher grade tooling, according to Buchenroth.