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Productive Times on Sun Manufacturing Co., 832-448-http://www.ctemag.com/aa_pages/2012/1201, www.sun-mfg.com. Challenge: Efficiently drill through-holes in 4130 steel parts. Solution: A modular, indexable-insert drill that eliminated pecking cycles. Solution Provider: Kennametal Inc., 800-446-7738, www.kennametal.com.
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Sun Manufacturing Co. is well established at making parts for the oilfield and subsea industries—companies that drill holes for a living. However, when the Houston job shop was drilling holes through the 8 "-thick flanges in a 4130 medium- to high-alloy steel part called a spool, it seemed like drilling holes to China. Each 2.375 "-dia. hole took about 30 minutes and the part has 44 such holes—24 on one side and the remainder on the other. In addition, drilling the holes made Sun’s 30-hp Kuraki KBT11Z CNC horizontal boring mill a bottleneck to accomplishing other work.
Courtesy of Kennametal
Steve Eldridge (right), shop superintendent for Sun Manufacturing Co., discusses the performance of Kennametal’s KSEM Plus modular drill (below) with David Hray, applications engineer at Kennametal.
According to Steve Eldridge, shop superintendent for Sun, the workpiece material isn’t particularly challenging to machine, having a hardness of about 212 to 235 HB and a tensile strength of about 75 ksi.
The holes were mounting holes without threads or a fine surface finish requirement, so Sun initially used a conventional holemaking method and applied a titanium-nitride-coated, 2.375 "-dia. spade drill. Because the spade drill had a single cutting edge, Sun had to run it in pecking cycles, which are usually performed to break chips so they are small enough to flow through the tool’s flutes without damaging the hole surface or drill.
For example, a variable-peck cycle could start with a 1 " peck, the tool would be retracted slightly to break the chips, and the next peck would go 0.50 " deeper, followed by one 0.25 " deeper, with the last peck going 0.05 " deeper than the previous peck. “It keeps continuously going back and forth until you finally complete the drill depth you need,” Eldridge said. “That adds to the drilling time because you’re cutting a lot of air instead of the material.”
The deeper the drill goes, the more difficult it is for coolant to reach the tool/workpiece interface, so pecking is also done to provide more coolant to the tool tip.
“We were certainly feeling pressure to decrease cycle time,” Eldridge said. “This part required both lathe work and mill work, so a complete job was taking in the area of 185 to 200 hours.”
Sun searched for a solution and solicited quotes from toolmakers. After producing four spools with the spade drill applied for drilling the flange hole, Sun switched to the KSEM Plus modular drill from Kennametal Inc., Latrobe, Pa., based on the recommendation of David Hray, applications engineer at Kennametal. In addition, Kennametal’s tool cost less than the other drills that Sun Manufacturing quoted. The KSEM Plus modular drill consists of a steel body coupled to an indexable-insert, high-strength steel head, and a single tool body accepts a range of drill-head sizes.
Like the spade drill, the modular drill has through-coolant capability but that’s where the similarities end. Instead of consuming about half an hour to drill one hole, the KSEM Plus drill was able to produce a hole in 1.6 minutes. Plus, the spade drill caused chips to coil up after 1 " to 3 " of depth, whereas the KSEM Plus geometry generated small C-shaped chips that were easily evacuated. The drill’s differential-helix flutes enhance chip evacuation, according to Kennametal.
Sun was feeding the spade drill at about 1 ipm and was able to increase that tenfold with the modular drill. And feeding faster is possible with the appropriate machine tool. “We could have run at 12 ipm, but it turns out we didn’t have the horsepower,” Eldridge said, noting that a call to the toolmaker’s customer application support line yielded new machining parameters. “I plugged in the new numbers and we were running again in 15 minutes.”
Although the shop only had three more of those spools to produce, Sun found the modular drill is suitable for other applications and continues to apply the tool whenever possible. “It was phenomenal,” Eldridge said. “We hadn’t seen anything that could provide this kind of drilling performance at the hole depths we needed. The KSEM Plus paid for itself on the first part.”
Related Glossary Terms
- Brinell hardness number ( HB)
Brinell hardness number ( HB)
Number related to the applied load (usually, 500 kgf and 3,000 kgf) and to the surface area of the permanent impression made by a 10mm ball indenter. The Brinell hardness number is a calculated value of the applied load (kgf) divided by the surface area of the indentation (mm2). Therefore, the unit of measure of a Brinell hardness number is kgf/mm2, but it is always omitted.
- boring
boring
Enlarging a hole that already has been drilled or cored. Generally, it is an operation of truing the previously drilled hole with a single-point, lathe-type tool. Boring is essentially internal turning, in that usually a single-point cutting tool forms the internal shape. Some tools are available with two cutting edges to balance cutting forces.
- computer numerical control ( CNC)
computer numerical control ( CNC)
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.
- coolant
coolant
Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.
- flutes
flutes
Grooves and spaces in the body of a tool that permit chip removal from, and cutting-fluid application to, the point of cut.
- hardness
hardness
Hardness is a measure of the resistance of a material to surface indentation or abrasion. There is no absolute scale for hardness. In order to express hardness quantitatively, each type of test has its own scale, which defines hardness. Indentation hardness obtained through static methods is measured by Brinell, Rockwell, Vickers and Knoop tests. Hardness without indentation is measured by a dynamic method, known as the Scleroscope test.
- inches per minute ( ipm)
inches per minute ( ipm)
Value that refers to how far the workpiece or cutter advances linearly in 1 minute, defined as: ipm = ipt 5 number of effective teeth 5 rpm. Also known as the table feed or machine feed.
- lathe
lathe
Turning machine capable of sawing, milling, grinding, gear-cutting, drilling, reaming, boring, threading, facing, chamfering, grooving, knurling, spinning, parting, necking, taper-cutting, and cam- and eccentric-cutting, as well as step- and straight-turning. Comes in a variety of forms, ranging from manual to semiautomatic to fully automatic, with major types being engine lathes, turning and contouring lathes, turret lathes and numerical-control lathes. The engine lathe consists of a headstock and spindle, tailstock, bed, carriage (complete with apron) and cross slides. Features include gear- (speed) and feed-selector levers, toolpost, compound rest, lead screw and reversing lead screw, threading dial and rapid-traverse lever. Special lathe types include through-the-spindle, camshaft and crankshaft, brake drum and rotor, spinning and gun-barrel machines. Toolroom and bench lathes are used for precision work; the former for tool-and-die work and similar tasks, the latter for small workpieces (instruments, watches), normally without a power feed. Models are typically designated according to their “swing,” or the largest-diameter workpiece that can be rotated; bed length, or the distance between centers; and horsepower generated. See turning machine.
- milling machine ( mill)
milling machine ( mill)
Runs endmills and arbor-mounted milling cutters. Features include a head with a spindle that drives the cutters; a column, knee and table that provide motion in the three Cartesian axes; and a base that supports the components and houses the cutting-fluid pump and reservoir. The work is mounted on the table and fed into the rotating cutter or endmill to accomplish the milling steps; vertical milling machines also feed endmills into the work by means of a spindle-mounted quill. Models range from small manual machines to big bed-type and duplex mills. All take one of three basic forms: vertical, horizontal or convertible horizontal/vertical. Vertical machines may be knee-type (the table is mounted on a knee that can be elevated) or bed-type (the table is securely supported and only moves horizontally). In general, horizontal machines are bigger and more powerful, while vertical machines are lighter but more versatile and easier to set up and operate.
- spade drill
spade drill
Flat end-cutting tool used to produce holes ranging from about 1" to 6" in diameter. Spade drills consist of an interchangeable cutting blade and a toolholder that has a slot into which the blade fits. In horizontal applications, universal spade drills can achieve extreme depth-to-diameter ratios, but, in vertical applications, the tools are limited by poor chip evacuation.
- tensile strength
tensile strength
In tensile testing, the ratio of maximum load to original cross-sectional area. Also called ultimate strength. Compare with yield strength.
