Modular units are often the best choice for flexibility and cost compared to solid tools
When weighing the choice of replaceable-tip mills and drills or solid-carbide tools, consider this succinct statement from one industry expert: carbide equals cost.
“Clearly, a small replaceable insert or tool head made of carbide costs less than an entire solid drill of the same diameter,” noted Andrew Pisorn, solid carbide product manager at Allied Machine & Engineering Corp., Dover, Ohio. And, by extension, using a range of replaceable-tip tools with a smaller number of steel body holders greatly improves operational and cost efficiencies by cutting down on one’s inventory of unique solid-carbide tools. “If your shop can minimize the amount of carbide in your tool cribs and drawers, you’re minimizing inventory costs.”
Jim White, national sales manager for Carmex Precision Tools LLC, Richfield, Wis., concurred. “The reason most customers go with indexable is versatility—using one holder for multiple pitches—or cost,” he said, adding that “indexable thread mills are more cost effective in large-thread diameter applications or low-volume jobs where cycle time is not a consideration.”
Another inventory factor to consider: Shops that routinely send solid-carbide tools for regrinding must keep an adequate supply of solid tools in reserve to maintain production, said Patrick Loughney, a product manager at Sandvik Coromant, Fair Lawn, N.J.
Replaceable-tip tools can also provide users with a significant reduction in setup times, Loughney added, for instance on transfer lines for automotive manufacturing. And, with the ever-pressing shortage of experienced manufacturing labor, quick and easy tool switchouts instead of more intensive setups help ease that burden.
However, any time an operator makes changes in the machine, something can always go wrong. For instance, they must take care not to drop wrenches and screws into the machine while replacing tools.
When to Use Replaceable Tips
But what about performance? Ultimately, using replaceable-tip drilling tools generally does not mean sacrificing much penetration rate or tool life—to a point—experts assert.
“For example, if I would expect to get a thousand inches of tool life with a solid, then I would expect the same from a modular tool—but of course exceptions apply,” said Bill Pulvermacher, director of marketing for YG-1 Tool Co., Vernon Hills, Illinois. “I would expect the overall penetration rate of the solid to be just a little bit higher.” Furthermore, some users say replaceable-tip drills over 0.5" (12.7 mm) tend to perform better in lathe applications “because they are much more tolerant of the misalignment that lathes tend to have.”
The current crop of replaceable-tip milling and drilling tools features a host of new substrates, geometries, PVD coatings and coolant solutions geared for a range of applications across numerous industries and materials. As always, the decision to use a particular tool is application specific.
When drilling difficult-to-machine materials like stainless steel or titanium, steel bodies for replaceables might torque too much, Pulvermacher cautioned. For that reason, fabricators have tended to split their use of solid and replaceable tools for those materials about 50-50, depending on the diameter. For that to change, he said, replaceable-tip tools would have to outperform solid in the 0.5-0.75" (12.7-19.05 mm) range. Replaceable-tip drills might get the nod in larger diameters, where solid drills could cost up to $750; however, replaceables struggle under 7/16" (11.11 mm) because they are somewhat expensive relative to solids—and the small tools, screws and inserts tend to get lost.
The Designated Drilling Tool
In terms of drilling, the number and type of holes to be made is generally the key determinant for opting to use replaceable-tip tools, according to Allied’s Pisorn. The more holes (from 1,000 to 50,000 or more) and the shallower (up to 13×D) the better.
YG-1 touts its 7×D drill as the only one of its type on the market, Pulvermacher noted. “People really like it because 8×D gives up so much rigidity.”
These drills are being used heavily in structural steel applications like beams and bracketing in areas such as bridge towers, Pisorn said. Planetary gears with flanges might feature 20 to 50 shallow holes; bearing rings for wind energy can feature 50-100 holes. Tube sheets for heat exchangers is another sound application. And, a filtration system plate for the paper industry might feature thousands of shallow holes.
Allied’s new GEN3SYS XT Pro drills feature dual gundrills with four outlets for increased coolant flow and material-specific inserts with coatings developed in-house. “A unique connection design offers superior torsional loads while still allowing the convenience of insert swaps while the tool remains in the spindle,” Pisorn said.
XT Pro carbide inserts have a combination of substrate coating and geometry engineered to survive the wear of high-penetration drilling, which “inherently produces significant heat,” Pisorn noted. “Combating that heat well is critical to extending tool life and increasing drilling rates. We have worked closely with our coating team and partners to develop several new material-specific, proprietary, multilayer coatings designed to withstand increased heat thresholds.”
Slated for release midyear is YG-1’s I-One drill. “We’re performing extensive testing with it in the energy industry, with very good success,” Pulvermacher noted. It will exist alongside the company’s well-established I-Dream drill, which currently has several geometries: Dream Drill General for general purpose (carbon steel, iron); one for stainless (Inox); Dream Drill Alu (aluminum), High Feed (carbon steel, iron); and High Hard (up to 70 HRC).
The initial release of the I-One will feature a single grade for the energy industry, with general-purpose grades and geometries to follow. I-One’s multilayer coating is geared to high or low speeds and is designed to tolerate heat and abrasion and prevent sticking. It is fully coolant-through.
Another drill that’s been on the market a while is the CoroDrill 870 series by Sandvik Coromant. But since its introduction in 2012, numerous refinements have been made. “We found that the body material was wearing, so we made it more wear-resistant, making the drill more rigid,” explained Loughney.
“The biggest thing we’ve done is introduced new grades optimized for steel, stainless steel and cast iron,” he continued. “Our Zertivo technology uses a PVD process, and we are able to achieve better bonding between the substrate and coating to where we have significant improvements in edge line security—resulting in longer, predictable tool life.” Grades include –PM 4334 for low alloyed and carbon steels, –MM2334 for stainless and –KM3334 for cast iron. While there is no grade specifically for heat-resistant materials, Loughney added, “we can cross over our geometries into those areas” for multiple industries.
Toolholding is vital to precision holemaking with replaceable-tip drills, he continued. “You have to remember that you have collective tolerances—of the body itself and then a tip on top of it.”
At Mitsubishi Materials U.S.A. Corp., Schaumburg, Illinois, the company’s DIAEDGE STAW indexable drills “are unique in that they have cutting edge geometry that is the same as the edge geometry on our DIAEDGE WSTAR solid-carbide drill,” said Barry Griggs, assistant business development manager of cutting tools. “The wave designed cutting edge and center point gash is aimed at improving machined hole accuracy.”
As a result, the DIAEDGE STAW demonstrates “excellent chip disposability and achieves high-efficiency machining,” Griggs noted. “STAW replaceable carbide tips/inserts are designed for extreme sharpness, precision, positioning and rigidity in our unique clamping system. The wavy edge design delivers a sharp peripheral edge to enhance cutting performance, complemented by a strong center point geometry for initial cutting at entry. A high helix offers a low-resistance drill pocket design that improves chip breaking for superior chip disposal.” The STAW’s clamping system has more material behind the tip for added strength and durability.
Inserts are available in sizes from 10-18.1 mm, and the VP15TF and DP5010 PVD coated grades feature tough carbide substrates and proprietary crystal coating technology. For machining a wide range of materials, from alloy steels to various types of stainless steel and cast iron, the VP15TF grade ranges from 100-400 sfm, Griggs added. “The drill body is made resistant to corrosion and abrasion by using a superior high-heat resistance alloy and a special surface treatment suitable to counter new hard-to-machine work materials.”
Milling Tools Double Down on Depth
To more than double the depths of cut previously available in its Multi-Master line of end mills, Iscar Metals Inc., Arlington, Texas, added replaceable-tip mills capable of reaching depths up to 1.5×D, said Tom Raun, chief technical officer.
The Mini-Mill series of tools—including Nanmill, Nan3feed, Heli4mill, Heli3mill and Micro3feed—complement Iscar’s solid-carbide tools with diameters starting at 0.312-0.75" (7.92-19.05 mm) with multi-edged inserts for 90o milling and fast-feed milling, he explained.
“Various grade options allow better flexibility and optimization vs. solid carbide tools” and feature proprietary Sumo Tec PVD post-coating technology that provides “improved toughness, improved flaking, and chipping resistance, which in turn provides very reliable and repeatable results.” Those grades are:
- IC810: AlTiCrN+TiN PVD coated for milling nodular cast iron at medium to high cutting speeds,
- IC808: TiAlN PVD coated, which has a hard, submicron substrate with excellent chipping resistance and high wear resistance for a wide range of materials, and
- IC830: AlTiN+TiN PVD coated for high toughness and wear resistance, which makes it ideal for interrupted cuts and heavy operations in steel, stainless steel and high-temperature alloys.
Also for hard-to-machine materials, Sandvik Coromant’s recently introduced CoroMill 316 exchangeable milling heads are optimized for titanium and nickel-based metals. For titanium, grade 1745 with its 1.5×D cutting edge “is a little bit longer of a replaceable-tip end mill compared to our standard 316s,” explained Scott Lewis, aerospace industry specialist for Sandvik Coromant. To be released in the near future is grade 1710 for nickel alloy, which will also have 1.5XD capabilities. Both grades feature unique substrates and geometries and are currently available in the company’s solid-carbide end mills. These replaceable-tip end mills “can run, cutting data wise, quite close to what a solid is, with a solid being perhaps more rigid because it is shorter—a stouter setup,” Lewis said. “We also have very short, stout adapters for our 316s.”
Diameters Large and Small
Fabricators seeking smaller diameters can look to Iscar’s SumoCham line, now available down to 4 mm in up to 5×D applications, said Craig Ewing, national product specialist for Iscar Metals.
SumoCham is available from 4-32.9 mm diameter in 0.1 mm increments, Ewing explained. Heads are offered in 10 geometries for various material groups and applications, and bodies are offered in 1.5×D, 3×D, 5×D, 8×D and 12×D through most of the diameter range. Each body accepts a range of head diameters: from 4-14.9 mm, bodies come in 0.5 mm increments, and from 15-32.9 mm, bodies come in 1-mm increments.
“Some smaller sizes come in smaller shank diameters and shorter OAL (overall length) without a flange for Swiss lathe and live tool applications,” he added. “There are also drill bodies with integrated chamfering inserts.”
On the larger side, Iscar’s LogIQ-3-Cham is a three-flute, interchangeable-head drill in 14-23.9 mm diameters, in 0.1-mm increments and bodies in 1.5×D, 3×D and 5×D. “Eventually, the line will include all head sizes from 12-25.9 mm. The three-flute design will provide extended tool life and/or increased feed rates,” mostly for ISO-P and ISO-K materials, Ewing said.
For deeper, large-diameter applications, the Iscar ModuDrill is a combination of replaceable head and indexable insert drills in larger diameters for depths beyond 12×D. The ChamIQ 700 family is offered in a diameter range of 33-40 mm in 0.5 mm increments and “some common fractional-inch increments,” he said. “The HFP carbide blades, which look more like a spade drill, fit into a range of steel adapter heads (MD-DFN), which also mount onto a long steel drill body (MD-BODY). A combination of two drill bodies and seven adapter heads cover the entire diameter range.”
The modular part of the system “is that there are indexable insert heads that also mount onto the two drill bodies,” said Ewing. They are offered in eight metric sizes (33-40 mm) and two inch sizes (1.375" and 1.5") and use standard SOMX inserts from the DR Twist line. “They also use guide pads from the BTA Deep Drill line. The drilling depth of this system is in the 16.5-17" [419-432 mm] range.”
Meanwhile, Kyocera Precision Tools Inc., Hendersonville, N.C. is noting increased demand for smaller, modular indexable end mills, said Technical Center Manager Brian Wilshire.
“These screw-in heads are available from 8 mm up to 32 mm in diameter and can be mounted on extensions of various lengths,” he explained. “The smaller diameters have replaced solid-carbide tools in many instances. The advantages of both the replaceable-tip drills and modular, indexable end mills are similar: lower replacement costs, because instead of the entire tool being composed of carbide, only the portion actually doing the cutting contains carbide; less variability in position after indexing; the ability to easily change grades or geometries when cutting different workpiece materials; and less downtime when replacing worn tools.” However, he added, solid-carbide tools still provide better rigidity, deep-hole drilling and greater depth of cut capabilities when milling.
The option of smaller diameter, high-feed end mills is “a popular option for harder tool and die steels, especially in the aerospace and mold industries,” Wilshire continued. “Customers tend to run the replaceable-tip drills and indexable end mills faster than their solid-carbide counterparts to shorten cycle times because the replacement costs are less and the time to index is shorter.”
PVD coatings are most common for smaller diameter tools, he added, “because they help maintain sharper edges than thicker CVD coatings. Kyocera’s R&D efforts in PVD coating technology have resulted in our Megacoat coatings. With high oxidation temperatures and high hardness, they are ideal for running at higher speeds, resulting in reduced cycle times.”
For large-diameter applications, true helical flutes are the key to the success of the SRH series of replaceable mills by Carmex, said White. Helical flutes cut freer than straight-flute tools, he explained, although “solid thread mills are still the most efficient choice for anything under 1" (25.4 mm) thread diameter because you get more flutes in the cut and the geometry allows for higher cutting speeds and faster feed rates.” The SRH has been most successful in the oil and gas market, threading buttress and Acme threads in large diameters, he added.
Carmex recently introduced new coatings for its Slim MT line. “This nano coating can handle temperatures 30 percent higher than TiAlN and is 25 percent harder than other coatings typically used for indexable cutters,” said White. “These coatings outperform others in high-temperature alloys like inconel and titanium.”
Studies in Success
Replaceable-tip cutting tool suppliers offer numerous examples of how those tools surpassed solid-carbide versions. For instance:
- Firearms: A customer producing cast aluminum upper receiver castings for AR rifles switched from a solid-carbide twist drill to Allied’s GEN3SYS XT Pro holder (HXT1024S-100F) and insert (XTN24-25.3) and reduced cost per hole by 108 percent while increasing tool life by 233 percent.
- Automotive: A major automotive manufacturer was using a solid-carbide drill to cut eight holes 12.4 mm in diameter and 10.7-mm deep in a carbon steel transmission part. Switching to Iscar’s replaceable-tip DCN 120-036-16R-3D with an ICP 0488 IC908 insert and IC908 grade reduced per-part costs by 46 percent, from 31 cents to 17 cents each. “There was also improved chip control, which eliminated tangled chips interfering with the automation equipment,” Ewing said. “There was no more downtime to remove chips from the tool.”
- Aerospace: An Iscar customer was using a 0.5" (12.7-mm), four-flute, solid-carbide end mill for a slotting/roughing operation on Inconel 718 at 50 units per month. By switching to Iscar’s HM390 ETPD.50-03-C.50-05C replaceable-tip end mill and grade IC808, total tooling cost dropped $8,343 per batch, Raun said.
- Tube sheet: A customer using a solid-carbide drill on duplex stainless steel was experiencing chipping due to inefficient plate support, causing the plate to flex, Griggs recalled. “When the drill would exit the hole, the plate would spring, causing the corners of the drill to chip and break.” By switching to Mitsubishi’s STAW, with its unique corner radius to strengthen the drill edge, the customer saved more than 10 times the cost of each solid drill.