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Productive Times on Tulsa Machine Works Inc., 918-834-0911. Challenge: Reduce tooling costs when milling crankshafts. Solution: Tool repair and modification services. Solution Provider: Carbide Tool Services Inc., 800-243-9577, www.carbidetool.com.
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Machining a crankshaft’s complex features and obtuse angles from solid bar stock is a metalworking challenge. Tulsa (Okla.) Machine Works routinely handles that challenge, producing a variety of crankshafts for pumps used in the petroleum industry. The tempered 4340 steel crankshafts are as large as 74 " long and 19 " in diameter and have as many as five throws.
Courtesy of Carbide Tool Services
Carbide Tool Services re-engineered and repaired damaged toolholding cartridges for Tulsa Machine Works at a fraction of the replacement cost. In addition, the cartridges’ top clamps received a chromium-nitride coating to minimize wear caused by chip flow.
Tulsa Machine performs the milling on a specialized CNC milling machine from American GFM. In the crankshaft milling process, the workpiece is stationary and a milling cutter with teeth on its ID orbits around the part to cut the features. In Tulsa Machine’s mill, the cutter is assembled from 56 segments, each of which supports a cartridge that holds a custom-geometry, coated carbide insert. New cartridges cost about $300 each, so replacing them when they wear represents a significant expense.
Seeking to control tooling costs, Tulsa Machine contacted Carbide Tool Services Inc., Anoka, Minn., which specializes in the repair of damaged indexable tooling, to determine if repairing the cartridges was a cost-effective alternative to replacement. According to Pat Hjelm, Carbide Tool Services’ cutting tool specialist, about 75 percent of the company’s business consists of repairing complex pocketed tools with tight tolerances. The company also provides engineering services for the design of new tools and for tool modifications.
To rebuild a worn or damaged tool, Carbide Tool Services uses a new insert as a gage and builds the tool pocket with proprietary weld materials. The pockets are then remachined, recalibrated and inspected.
During the repair process for Tulsa Machine’s tooling, Carbide Tool Services analyzed the causes of cartridge wear and made recommendations regarding ways to modify the cartridges to improve wear performance. “There was some interference with the cartridge on the workpiece,” Hjelm said. “That’s when we decided to take a look at altering the cartridges themselves. We came up with the idea to add an extra 10° of side and end clearance to the cartridges. That would allow the tools to cut with no possibility of rubbing on the workpiece.”
Further modifications involved the cartridge’s top clamps. “The chips that were coming off the workpiece were hard and abrasive and were starting to chew right through the steel clamp,” Hjelm said.
To reduce the wear caused by chip wash, Carbide Tool Services recommended that a chromium-nitride coating be applied to the clamp. Preparation of the clamp was critical for the coating to be successful. “We polished and blasted the clamp before we did the coating,” Hjelm said. “The smoother we can get that surface, the more evenly the coating will go on.” In addition to providing a higher degree of wear resistance, the coating served to smooth chip flow and lessen the tendency of chips to stick to the clamp and holder.
The per-cartridge repair cost of $95 represented a substantial savings. “We’ve run the repaired cartridges for about 6 months now, and they are holding up real well,” said Forrest Rogers, president of Tulsa Machine.
In addition to saving tooling replacement costs, tool repair can also save time. For complex custom tools, “We can turn a repair around in a day, while it might take 10 to 12 weeks to get a new tool built,” Hjelm said. He noted that in hard economic times, Carbide Tool Services’ business actually grows, “because everyone is looking for cost savings.”
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.
- 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.
- gang cutting ( milling)
gang cutting ( milling)
Machining with several cutters mounted on a single arbor, generally for simultaneous cutting.
- inner diameter ( ID)
inner diameter ( ID)
Dimension that defines the inside diameter of a cavity or hole. See OD, outer diameter.
- metalworking
metalworking
Any manufacturing process in which metal is processed or machined such that the workpiece is given a new shape. Broadly defined, the term includes processes such as design and layout, heat-treating, material handling and inspection.
- 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.
- milling machine ( mill)2
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.
- wear resistance
wear resistance
Ability of the tool to withstand stresses that cause it to wear during cutting; an attribute linked to alloy composition, base material, thermal conditions, type of tooling and operation and other variables.
