From machines to putting greens

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

Not many machine shops serve as broad a variety of customers as Rayco Machine & Engineering Group Inc., Indianapolis. Rayco makes parts for Indianapolis racecars, builds assemblies for U.S. troops overseas, machines aerospace components and manufactures 292 part numbers for Allison Transmission Inc. 

The shop’s work also includes oddball one-offs. “A chocolatier brought a broken brass piece to us from an old German chocolate-making machine,” said Greg Cox, company president. “We reverse-engineered the part, made it and got their machine back up and running. It never ceases to amaze me how many different projects we get into.” 

One out-of-the-ordinary project evolved from prototype work to production. Rayco machines more than half the components for the RG3 robotic greens mower from Precise Path Robotics, which is engineered to boost golf course labor productivity.

A typical part is a roller drive rear spindle. More than 3 " long with a major diameter less than 3 ", the part is machined from 3 "-dia. 4140 steel bar prehardened to 28 to 32 HRC and sawed to 3.560 " lengths. 

To begin the machining process, the sawed bar is chucked in a 4 "-dia. Hardinge step chuck in a Hardinge Talent SV 150 lathe. Facing is the first step, using a Sumitomo CNMG 432 coated carbide insert, followed by axial drilling with a No. 2 center drill. The part is roughed via a V71 canned cycle at a 0.075 " DOC, 0.012-ipr feed rate and 600-sfm cutting speed. The operation cuts three diameters, leaving 0.010 " of excess stock for finishing. 

The first 2.198 " of bar length is turned to a diameter of 0.760 ", the 0.484 " length is turned to 1.010 " and the 0.130 " length is turned to 1.450 ". “We blend off of the part at that point to create a radius at a 2.950 " diameter,” Cox said, explaining that when the part is later flipped in the chuck and finished, blending into the radius assures there will be no sharp edge on that corner. 

The finishing insert that’s applied next is a CNMG 431, which has a smaller nose radius than the CNMG 432 to make the resulting shoulders as small as possible. For the 0.010 "-deep finish pass, Rayco increases the speed to 750 sfm. Finished diameters of the segments are 0.750 ", 1.00 " and 1.440 ". Cox said the pass produces a finish of 37 µin. Ra. This first set of operations consumes 2 minutes and 36 seconds. 

After the tailstock is removed and a 0.257 "-dia. cobalt tap drill makes a 0.910 "-deep axial hole, a 90° countersink puts a chamfer on the hole mouth. Then a 5⁄16-18 tap threads the hole 5⁄8 " deep. These four operations take 1 minute. The part is then turned in the chuck and gripped on the 1.00 "-OD segment, locating against the face of the 1.440 "-dia. segment. 


Courtesy of Rayco Machine & Engineering Group

Among the parts that Rayco Machine & Engineering Group machines for the Precise Path RG3 robotic greens mower is this steel roller drive rear spindle (above). Below: The Precise Path RG3 robotic greens mower, with a guidance beacon in the background. 

Courtesy of Precise Path Robotics

The next operation employs a G72 canned cycle to face the part and rough turn a 0.248 "-long 1.260 " diameter, again leaving 0.010 " of excess material. A Kennametal NG2031 RK Top Notch grooving tool then puts an undercut at the back of the 1.260 " diameter next to the part face to provide a place to turn into during finishing.

After a ¾ "-dia. drill creates a 0.625 "-deep hole in the end of the bar, a Sumitomo ½ "-dia. boring bar, tooled with a TCNP221 coated carbide insert, bores the hole to a diameter of 0.644 ". The CNMG 431 turning tool with a 0.015 " nose radius is again employed to finish bore the back face, the 1.250 " diameter and the part’s overall length. Final size of the large diameter is 2.940 ", and part length is 3.331 ". These three operations consume 1 minute and 35 seconds. 

Then Rayco moves the part to its Hurco VM20 vertical machining center, chucking it vertically on the 1.0 " OD in a Hardinge indexer, to drill four bolt through-holes. Before a standard cobalt jobber drill produces the 0.332 "-dia. holes, a 90° spotfacer cuts a 0.350 "-dia. chamfer at each hole site. 

When the holes are done, the indexing head is tilted 90° and the bar is clamped horizontally in a collet that has locating pins located to match two of the bolt holes. The pins assure the keyway to be machined next will be positioned correctly in relation to the holes. 

A 4-flute, 3⁄16 "-dia., solid-carbide endmill then machines a 1.090 "-long, 0.106 "-deep, 0.118 "-wide keyway, beginning at the 0.750 "-dia. end of the bar. The operations on the VMC take 3 minutes and 30 seconds. With machining completed, the shaft is sent out for zinc plating with yellow hexavalent chromate. 

“This is a pretty simple part,” Cox said, noting that Rayco’s participation in the project began about 2 years ago with the machining of prototype parts. Many of the parts were changed during the product development process, and Rayco provided engineering and design-for-manufacturing assistance during that time. First-year production quantities for the RG3 mower are targeted at 250 units, Cox noted, with volume expected to increase. 

For more information about Rayco Machine & Engineering Group Inc., visit www.ray or call (317) 291-7848. To learn more about the Precise Path RG3 Robotic greens mower and its manufacturer, visit CTE

About the Author: Bill Kennedy, based in Latrobe, Pa., is a contributing editor for CTE. He has an extensive background as a technical writer. Contact him at (724) 537-6182 or

Related Glossary Terms

  • 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.

  • boring bar

    boring bar

    Essentially a cantilever beam that holds one or more cutting tools in position during a boring operation. Can be held stationary and moved axially while the workpiece revolves around it, or revolved and moved axially while the workpiece is held stationary, or a combination of these actions. Installed on milling, drilling and boring machines, as well as lathes and machining centers.

  • canned cycle ( fixed cycle)

    canned cycle ( fixed cycle)

    Subroutine or full set of programmed NC or CNC steps initiated by a single command. Operations are done in a set order; the beginning condition is returned to when the cycle is completed. See CNC, computer numerical control; NC, numerical control.

  • center drill

    center drill

    Drill used to make mounting holes for workpiece to be held between centers. Also used to predrill holes for subsequent drilling operations. See centers.

  • chuck


    Workholding device that affixes to a mill, lathe or drill-press spindle. It holds a tool or workpiece by one end, allowing it to be rotated. May also be fitted to the machine table to hold a workpiece. Two or more adjustable jaws actually hold the tool or part. May be actuated manually, pneumatically, hydraulically or electrically. See collet.

  • collet


    Flexible-sided device that secures a tool or workpiece. Similar in function to a chuck, but can accommodate only a narrow size range. Typically provides greater gripping force and precision than a chuck. See chuck.

  • countersink


    Tool that cuts a sloped depression at the top of a hole to permit a screw head or other object to rest flush with the surface of the workpiece.

  • cutting speed

    cutting speed

    Tangential velocity on the surface of the tool or workpiece at the cutting interface. The formula for cutting speed (sfm) is tool diameter 5 0.26 5 spindle speed (rpm). The formula for feed per tooth (fpt) is table feed (ipm)/number of flutes/spindle speed (rpm). The formula for spindle speed (rpm) is cutting speed (sfm) 5 3.82/tool diameter. The formula for table feed (ipm) is feed per tooth (ftp) 5 number of tool flutes 5 spindle speed (rpm).

  • 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.

  • feed


    Rate of change of position of the tool as a whole, relative to the workpiece while cutting.

  • grooving


    Machining grooves and shallow channels. Example: grooving ball-bearing raceways. Typically performed by tools that are capable of light cuts at high feed rates. Imparts high-quality finish.

  • 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.

  • machining center

    machining center

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

  • outer diameter ( OD)

    outer diameter ( OD)

    Dimension that defines the exterior diameter of a cylindrical or round part. See ID, inner diameter.

  • robotics


    Discipline involving self-actuating and self-operating devices. Robots frequently imitate human capabilities, including the ability to manipulate physical objects while evaluating and reacting appropriately to various stimuli. See industrial robot; robot.

  • spotfacer


    Tool, guided by a pilot, used to machine a recess around a hole.

  • tap


    Cylindrical tool that cuts internal threads and has flutes to remove chips and carry tapping fluid to the point of cut. Normally used on a drill press or tapping machine but also may be operated manually. See tapping.

  • 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.

  • undercut


    In numerical-control applications, a cut shorter than the programmed cut resulting after a command change in direction. Also a condition in generated gear teeth when any part of the fillet curve lies inside of a line drawn tangent to the working profile at its point of juncture with the fillet. Undercut may be deliberately introduced to facilitate finishing operations, as in preshaving.