Drilling without catastrophe

Author Cutting Tool Engineering
August 01, 2011 - 11:15am


END USER: Three Sigma Manufacturing Inc., (253) 395-1125, www.threesigma.net. CHALLENGE: Improve cycle times and prevent catastrophic failure when drilling a hole in a complex aerospace part. SOLUTION: A replaceable-tip drill that reduced cycle times and provided progressive failure indicators. SOLUTION PROVIDER: Allied Machine & Engineering Corp., (800) 321-5537, www.alliedmachine.com


Three Sigma Manufacturing Inc. is a Tier 2 supplier that has been in the aerospace supply chain since the 1980s and has 21 employees. Commercial airplane parts is its primary line of work, but the Kent, Wash.-based company also makes parts for the firearms industry and marine industry, including hydraulic actuators and propellers for race boats. 

One aerospace part Three Sigma was looking to produce more efficiently was a guide fitting made of 15-5 PH solution annealed-condition stainless steel. Three Sigma has been making the part since 1997. “It is a reasonably complex part that goes in the overhead exit wing door of an airplane,” said Ken Frankel, company president. “It is a guide fitting with deep counterbores.” Three Sigma makes about 2,500 of these parts per year.

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Courtesy of Three Sigma Manufacturing

With the GEN3SYS replaceable-tip drill from Allied Machine (seen below), Three Sigma Manufacturing reduced drilling time by about 75 percent and tripled tool life compared to a previously used spade drill. GEN3SYS drills are in the No. 9 position of the Okuma lathe’s upper turret and in the No. 4 position of the lower turret. (Position numbers are visible in the photo above.)

Allied GEN3SYS(300).psd

Courtesy of Allied Machine

The part starts as a 15-lb. workpiece and weighs 2 lbs. when finished. The largest diameter on the 9.5"-long part is 2.5". 

One operation requires the part to be drilled and turned at the same time to produce more than one feature. In addition, the part requires four different turning operations, a milling operation and a few manual processes. The turning and drilling is performed on an Okuma LU300 lathe, with 80-psi through-coolant capability.

The part requires a 0.9843"-dia., 5.0"-deep blind-hole. Previously, the company applied a spade drill with a TiAlN-coated HSS bit at 329 rpm and 0.005 ipr, which calculates to 1.645 ipm.

Drilling, including spot drilling, took more than 4 minutes. Tool life was 30 parts.

Looking for performance improvement, Dave Fitzpatrick, vice president of Three Sigma, asked Allied Machine & Engineering Corp., Dover, Ohio, about the GEN3SYS replaceable-tip drill he saw at IMTS. 

Three Sigma was able to run the drill at 679 rpm and 0.008 ipr, which calculates to 5.43 ipm. It finished a hole in 55 seconds, tool life increased to more than 90 parts, and spot drilling was eliminated.

While Three Sigma appreciated the reduced cycle time and increased tool life, the company also required a tool that progressively wears rather than suddenly fails. According to Frankel, GEN3SYS predictably wears. “The nature of the failure is a key criterion that determines to what extent you can use the tool,” he said. “Can you use it to 90 percent of its life, or do you get scared at 50 percent and change it out?”

Frankel explained that Three Sigma tried various drills over the years and found one that produced a hole as needed, but when it failed, it was catastrophic. That failure not only damaged the tool body and insert beyond repair but also affected the machine, “forcing us to do a 5-hour realignment,” he said.

Predictable tool behavior provides the machinist with wear indicators. These include sounds, chip size and machining load, which Three Sigma’s machines monitor.

“Another indicator is visual,” Fitzpatrick said. “We see deterioration of the point and where it chips on the outer margins.”

In addition, GEN3SYS effectively evacuates chips. “Sometimes with the old drill we would have some chip wrap,” Fitzpatrick said. “This one tends to do less of that.”

According to Greg Torres, AMEC’s sales manager, 15-5 stainless steel is difficult to machine. “Sometimes it’s hard to break the chip, or the chips are stringy,” he said. “The GEN3SYS has the right kind of geometry to make it work.”

To reduce downtime, a machinist can change the drill’s replaceable tip without removing the holder from the machine. To extend tool life, the AM200 multilayer coating provides lubricity. “The resulting finish was also a success,” Torres said. “The drill produces a very good finish and keeps the hole concentric. It doesn’t require lot of thrust like a spade drill does.” 

Overall, the GEN3SYS met Three Sigma’s requirements for performance and productivity improvement.

“More than cycle times, we want to know what we yield per shift or per day,” Frankel said. “If the machine is running and the machinist can be doing something else 10' or 20' away, then yield for the shop goes up dramatically. Our question isn’t how much is it costing to make this hole, but how much more is our shop producing a day by using this drill.”

Related Glossary Terms

  • blind-hole


    Hole or cavity cut in a solid shape that does not connect with other holes or exit through the workpiece.

  • gang cutting ( milling)

    gang cutting ( milling)

    Machining with several cutters mounted on a single arbor, generally for simultaneous cutting.

  • high-speed steels ( HSS)

    high-speed steels ( HSS)

    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.

  • 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


    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.

  • lubricity


    Measure of the relative efficiency with which a cutting fluid or lubricant reduces friction between surfaces.

  • milling


    Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.

  • sawing machine ( saw)

    sawing machine ( saw)

    Machine designed to use a serrated-tooth blade to cut metal or other material. Comes in a wide variety of styles but takes one of four basic forms: hacksaw (a simple, rugged machine that uses a reciprocating motion to part metal or other material); cold or circular saw (powers a circular blade that cuts structural materials); bandsaw (runs an endless band; the two basic types are cutoff and contour band machines, which cut intricate contours and shapes); and abrasive cutoff saw (similar in appearance to the cold saw, but uses an abrasive disc that rotates at high speeds rather than a blade with serrated teeth).

  • 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.

  • turning


    Workpiece is held in a chuck, mounted on a face plate or secured between centers and rotated while a cutting tool, normally a single-point tool, is fed into it along its periphery or across its end or face. Takes the form of straight turning (cutting along the periphery of the workpiece); taper turning (creating a taper); step turning (turning different-size diameters on the same work); chamfering (beveling an edge or shoulder); facing (cutting on an end); turning threads (usually external but can be internal); roughing (high-volume metal removal); and finishing (final light cuts). Performed on lathes, turning centers, chucking machines, automatic screw machines and similar machines.