Made in America: repeatable precision

Author Cutting Tool Engineering
Published
March 01,2010 - 11:00am

Henry Repeating Arms Co., Bayonne, N.J., sells collectable repeating rifles and vows its products “will only be made in America or they won’t be made at all.” Helping fulfill that pledge is Lesleh Precision Inc. (LPI), Belle Vernon, Pa., which machines aluminum-bronze receivers and trigger plates for Henry Repeating Arms’ version of the 147-year-old-design, lever-action rifle that “won the West.”

LPI has been providing CNC machining services to the electrical, mining, military and other industries since 1999. About 2 years ago, following a reference from PIAD Precision Casting, Greensburg, Pa., which makes castings for the receivers, LPI began machining the castings. 

The machining process that LPI developed for the approximately 7.5 "×1.8 "×1.3 " receivers emphasizes efficiency and quality. Kevin Yuhas, LPI’s manufacturing engineer, programmed the parts in GibbsCAM, noting that the aluminum-bronze casting material “makes pretty nice chips, but it is abrasive.” As a result, most of the machining is done with coated carbide tools, primarily from Iscar Metals. “We’ve had good luck using their tools with carbide shanks and screw-on cutting heads for milling,” he said. 

Much of the machining is accomplished in two groups of operations performed on two Doosan Daewoo horizontal machining centers. To maximize throughput in the first set of operations, LPI designed a fixture to hold eight castings at a time. The shop enlisted PRZ Technologies, Lancaster, N.Y., a builder of hydraulic and manual workholders, to engineer hydraulics for the fixtures, which LPI’s machinist built in-house.

Key operations performed in the first fixturing include drilling an axial 0.681 "-dia. hole for the cartridge magazine and using a custom solid-carbide, through-coolant drill applied at 2,000 rpm and 10 ipm. Then, to accept the threaded end of the octagonal rifle barrel, a 0.702 "-dia. hole is drilled above the magazine hole and threaded with an Iscar ¾×20 thread mill. Project Engineer Tom Lofink said making the thread “is a little tricky” because it must be timed, or started, at a certain location to assure that when the barrel is screwed into the receiver at a specified torque, the flats on the barrel line up with the receiver’s top and side surfaces. Yuhas said Henry Arms provided a reference point at which he programmed the thread to begin. 

Other operations performed in the first fixturing include milling of various contours, drilling and tapping. Tolerances are generally ±0.002 ".

When the operations on the first machine are complete, the receivers are loaded into a vibratory deburring unit where they are tumbled in a ceramic medium for about 30 minutes. 

LelsehPrtT3-10.tif

Courtesy of B. Kennedy

In a process that includes custom fixtures and tools, Lesleh Precision machines an aluminum-bronze casting (right) for the receiver of a lever-action rifle. 

In the second HMC, a fixture holds four receivers at a time. Contours of the receiver sides are milled with an Iscar 1¼ "-dia. endmill tooled with two inserts and run at 4,000 rpm and 33 ipm. Yuhas said the cutting parameters are “not particularly fast” and were chosen to minimize vibration generated by the relatively large tool and thereby preserve surface finish. Next, a ½ "-dia., solid-carbide, ballnose mill radiuses the edges of the receiver at 9,000 rpm and 120 ipm. The tool runs fast “because we can,” Yuhas said. “We just kept pushing it and settled on something where we weren’t getting a lot of tool wear and it was getting done fast.” Other operations in this fixturing include drilling and tapping bolt holes in the sides of the receiver. 

Depending on demand, LPI makes about 500 receivers a week, including one version for 0.30-30 cartridges and another to accommodate 0.357, 0.44 magnum and 0.45 caliber rounds. 

After the operations on the two HMCs, the receivers move to a vertical machining center with three different fixtures on the machine table. Three sets of operations take place on the machine, and the operator moves the receivers in sequence from fixture to fixture as the operations are completed. 

In the first fixture, an Iscar 5⁄16 "-dia. interchangeable-head milling cutter plunges into the part to cut a 0.530 "-wide × 2.90 "-long ejection port slot and put a 0.040 "×45° chamfer on the slot edge. The endmill also machines some details in the receiver interior. 

In the second fixture, LPI employs a custom T-shaped, 2-flute keyseat cutter manufactured by Custom Tool and Grinding, Washington, Pa., to cut an interior slot that provides clearance for the rifle lever. The flutes span a diameter of 0.750 " but are only 0.480 " wide × 0.188 " thick, enabling them to fit through the 0.530 "-wide ejector slot cut in the previous fixturing. The tool is stationary when it is moved down through the ejector slot, spins to cut the clearance feature and then is stopped for withdrawal. Yuhas, who designed the cutter, said, “It doesn’t run real fast–1,000 rpm and 7 ipm–due to its small 0.250 "-dia. shank.” A 3mm-dia., 2-flute endmill with a relatively long 1¾ " reach then finishes interior details. 

In the last fixture on the VMC, a 0.156 "-dia., solid-carbide endmill machines a 0.050 "-deep × 1.0 "-long × 0.156 "-wide pocket where the serial number will be engraved. 

A locking bolt slot inside the receiver features square shoulders that can’t be cut with a round endmill, so the receiver next goes to a punch press, where it is clamped in a hydraulic fixture for broaching. “We get the slot as close as we can with the endmill, but broaching is the only way to make the square shoulders,” Lofink said. “We go down in one shot with an M-2 steel broaching tool from Anchor Danly Co.” The tool cuts the square corners and 0.005 " to 0.006 " from each side of the slot. 

Finally, the receivers are put in a programmable Pannier Corp. engraving machine, where each one is marked with an individual serial number. 

Total cutting time per receiver is 44 minutes, but a part is completed every 18 minutes because of the way they are cycled through the HMCs. CTE

For more information about Lesleh Precision Inc., call (724) 489-4538 or visit www.lesleh.com.

Related Glossary Terms

  • abrasive

    abrasive

    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.

  • broaching

    broaching

    Operation in which a cutter progressively enlarges a slot or hole or shapes a workpiece exterior. Low teeth start the cut, intermediate teeth remove the majority of the material and high teeth finish the task. Broaching can be a one-step operation, as opposed to milling and slotting, which require repeated passes. Typically, however, broaching also involves multiple passes.

  • centers

    centers

    Cone-shaped pins that support a workpiece by one or two ends during machining. The centers fit into holes drilled in the workpiece ends. Centers that turn with the workpiece are called “live” centers; those that do not are called “dead” centers.

  • clearance

    clearance

    Space provided behind a tool’s land or relief to prevent rubbing and subsequent premature deterioration of the tool. See land; relief.

  • 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.

  • endmill

    endmill

    Milling cutter held by its shank that cuts on its periphery and, if so configured, on its free end. Takes a variety of shapes (single- and double-end, roughing, ballnose and cup-end) and sizes (stub, medium, long and extra-long). Also comes with differing numbers of flutes.

  • fixture

    fixture

    Device, often made in-house, that holds a specific workpiece. See jig; modular fixturing.

  • 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.

  • gang cutting ( milling)

    gang cutting ( milling)

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

  • grinding

    grinding

    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.

  • 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.

  • machining center

    machining center

    CNC machine tool capable of drilling, reaming, tapping, milling and boring. Normally comes with an automatic toolchanger. See automatic toolchanger.

  • milling

    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.

  • milling cutter

    milling cutter

    Loosely, any milling tool. Horizontal cutters take the form of plain milling cutters, plain spiral-tooth cutters, helical cutters, side-milling cutters, staggered-tooth side-milling cutters, facemilling cutters, angular cutters, double-angle cutters, convex and concave form-milling cutters, straddle-sprocket cutters, spur-gear cutters, corner-rounding cutters and slitting saws. Vertical cutters use shank-mounted cutting tools, including endmills, T-slot cutters, Woodruff keyseat cutters and dovetail cutters; these may also be used on horizontal mills. See milling.

  • 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.

  • shank

    shank

    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.

  • tapping

    tapping

    Machining operation in which a tap, with teeth on its periphery, cuts internal threads in a predrilled hole having a smaller diameter than the tap diameter. Threads are formed by a combined rotary and axial-relative motion between tap and workpiece. See tap.