Finish Line

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

Related Glossary Terms

  • barrel finishing

    barrel finishing

    Mass finishing process that involves low-pressure abrasion resulting from tumbling workpieces in a barrel (usually of hexagonal or octagonal cross section) together with an abrasive slurry. See finishing.

  • black oxide

    black oxide

    Black finish on a metal produced by immersing it in hot oxidizing salts or salt solutions.

  • 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.

  • 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.

  • corrosion resistance

    corrosion resistance

    Ability of an alloy or material to withstand rust and corrosion. These are properties fostered by nickel and chromium in alloys such as stainless steel.

  • 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.

  • galling

    galling

    Condition whereby excessive friction between high spots results in localized welding with subsequent spalling and further roughening of the rubbing surface(s) of one or both of two mating parts.

  • 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.

  • hard turning

    hard turning

    Single-point cutting of a workpiece that has a hardness value higher than 45 HRC.

  • just-in-time ( JIT)

    just-in-time ( JIT)

    Philosophy based on identifying, then removing, impediments to productivity. Applies to machining processes, inventory control, rejects, changeover time and other elements affecting production.

  • lubricity

    lubricity

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

  • 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.

  • polishing

    polishing

    Abrasive process that improves surface finish and blends contours. Abrasive particles attached to a flexible backing abrade the workpiece.

  • toolholder

    toolholder

    Secures a cutting tool during a machining operation. Basic types include block, cartridge, chuck, collet, fixed, modular, quick-change and rotating.

  • turning

    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.

  • 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.

  • web

    web

    On a rotating tool, the portion of the tool body that joins the lands. Web is thicker at the shank end, relative to the point end, providing maximum torsional strength.

When applying finishes to parts, shops have a key choice: outsource or DIY.

Many manufacturers apply finishes such as black oxide, metal plating, adhesives and sealants to their parts. One key question is whether to apply those finishes in-house or outsource the operation. For many shops, the decision is based on part volume, cost of capital and practical considerations. 

For example, toolholder manufacturer Briney Tooling Systems Inc. has chosen to finish its products in-house. The Bad Axe, Mich., company produces conventional, HSK and shrink-fit holders in a variety of configurations and sizes.

100_0645.tif

Courtesy of KC Jones Plating

Machined aluminum receivers for automatic rifles run through an electroless nickel-boron plating line at KC Jones. The company reports that its process provides wear-resistant deposits harder than 68 HRC after heat treatment.

“Our toolholders come with one of two finishes: black oxide or polished,” said Justin London, sales engineer. “Do toolholders need to look pretty? Honestly, no. But it’s about aesthetics—trying to eliminate turn marks and other cosmetic issues and make the parts look nice.”

The company’s standard toolholders, such as shell mill adapters, side lock endmill adapters and collet chucks, are made from 8620 steel and receive a black-oxide finish. Previously, these parts were heat treated and hard turned prior to finishing, London noted. However, Briney recently changed its process to replace hard turning with centrifugal barrel polishing to prepare the surface for application of the black oxide. Parts are finished by grinding the spindle mating surfaces and other areas where black oxide is not required.

Shrink-fit and HSK toolholders, which now make up about 60 percent of Briney’s sales, are a different matter. “Those are made from H-13 tool steel, and black oxide won’t stick to H-13 without some extra processes,” London explained. “So our HSK and shrink-fit toolholders only get polished and then are sent to finish grinding.”

According to London, Briney was able to justify installation of the centrifugal barrel finishing process by comparing costs for hard turning to the investment needed to install and operate the finishing process. “That’s standard procedure,” he said. “Whenever there’s a finishing process that we don’t have in-house, we source it until the demand becomes large enough to make sense. That means it would increase profits by adding the process to our plant.”

Plating Pitfalls

Briney’s toolholder manufacturing operation is more the exception than the rule. Most part manufacturers simply don’t have the part volumes, the floor space for a finishing line or the in-house expertise to efficiently run a finishing operation. Still, many machined components use plated finishes to improve wear and corrosion resistance and to enhance aesthetics. And, there’s money to be made by supplying customers with parts that have more value added.

However, plating is a mysterious process to many manufacturers. To the uninitiated, a plating line can look like a giant chemistry experiment run amok. Plating processes require multiple tanks of hot chemicals, a means to move parts between the tanks and, for optimal results, tight control of process parameters such as temperature, time in the tank, chemistry of the various solutions and (for electroplating processes) amperage. Factor in increasingly stringent environmental regulations, and plating is a process that most shops are wise to outsource.

briney shrinkers.tif

Courtesy of Briney Tooling Systems

Produced from H-13 tool steel, Briney’s shrink-fit toolholders receive only a polish in a centrifugal barrel finishing system before finish grinding. The company’s 8620 alloy steel conventional toolholders, however, are blackened in-house.

The issue then becomes vendor selection, and it’s no longer good enough to simply send parts to the nearest plating shop that offers the needed process, according to Brian Harrick, vice president of operations for KC Jones Plating Co., Hazel Park, Mich. 

The company has about 100 employees and also operates plants in Warren, Mich., and Columbia City, Ind. Its 35,000-sq.-ft. Hazel Park plant is mainly for high-volume zinc, electroless nickel and bronze plating of automotive components. Workers at a 30,000-sq.-ft. facility in Warren apply adhesives and sealants to fasteners and other parts, while the 30,000-sq.-ft. Columbia City plant provides plating and electropolishing services. 

Harrick noted that many potential customers find his operation based on Internet searches. “Like a lot of shops, we relied on word of mouth to generate new business, but that wasn’t getting us very far,” Harrick said. “So when the economy hit the skids, we took the opportunity to update our Web site.

mbp-3-l.tif

Courtesy of KC Jones Plating

KC Jones’s proprietary Miccrolloy bronze plating process creates deposits 0.0001" to 0.1" thick on steel and cast iron parts, providing strength and wear resistance.

“Now, 25 percent of all our new leads come directly via the Web site,” he continued. “Of those, we’re converting about 70 percent into new business.”

According to Harrick, customers and prospects visit KC Jones’s Web site seeking information about specific coatings or properties, such as wear and corrosion resistance. “We don’t post coating specifications,” he said. “Instead, people are looking for keywords, such as nickel boron or zinc nickel, that their customers are asking about.”

Quality Factors

That brings Harrick to his next important selection factors: quality and delivery. Those are just the price of entry into many markets for plating shops like KC Jones, especially in the automotive market. “Customers and potential customers take for granted that you are ISO 9001 certified and can turn around parts on a just-in-time schedule,” he said. “Other markets require other certifications. For example, it’s hard to make much headway in the aerospace market without Nadcap certification (National Aerospace and Defense Contractors Accreditation Program) for your processes.”

Perhaps more important than quality certifications is a willingness to work with customers to define their needs and select the right plating deposit for the application. “We still see a lot of prints that say ‘plate to spec.’ We prefer to work with the customer to understand the part function and go from there,” Harrick said.

BC Automated Line.tif

Courtesy of Birchwood Casey

Birchwood Casey supplies complete systems for in-house blackening, including a CNC system that automates the process for higher volumes.

“Our ideal situation is, we sit down with customers and find out what they really need,” he added. “Where are the problems? What do they really need the part to do? We take the part, go into our lab and determine what the best coating is and develop the process. Ideally, our customers will allow us to do a bit of engineering work and become more of a partner. Some platers will just ‘dip it and ship it,’ but most want to understand the application and what the customer is looking for in terms of part performance.”

Harrick said an example of where manufacturers may not know the best plating choice for their parts is hard chromium—long the standard finish for wear and corrosion resistance. “Hard chromium is still viable—it’s the cheapest and easiest, and it does the job,” he said. “Now hexavalent chromium plating is being replaced by trivalent processes, which are not as highly regulated. But companies, a lot of OEMs in particular, are just hearing ‘chrome’ in general and are starting to ask what else is out there.” Electroless nickel and nickel-boron deposits are two potential replacements for hard chrome, depending on the application, he added.

According to Harrick, another consideration when evaluating potential plating suppliers is their ability to handle the required part volumes. KC Jones can handle daily part volumes of thousands of pieces, but small-volume jobs are more common. Therefore, Harrick recommends machine shops ask specifically about the plater’s ability to process low part volumes and provide quick turnarounds. He asked: “Are there additional charges for running small quantities versus larger lots? Can you turn around parts in 24 hours or less? And, what other services do you offer that I may need in the future?”

Dedicated to DIY

While many shops outsource part finishing operations, under some circumstances, in-house finishing can be beneficial, according to one supplier of blackening processes for ferrous and aluminum parts. Mark Ruhland, vice president of finishing equipment manufacturer Birchwood Casey, Eden Prairie, Minn., noted that in-house, black-oxide finishing, for example, can effectively control quality, scheduling and costs.

“Manufacturers that ship parts to an outside plant for black-oxide finishing incur extra costs and turnaround times that make it difficult to satisfy customer demands,” he said. “Outsourcing also requires higher in-process inventory levels and makes it impossible to have direct control over quality.”

According to Ruhland, in-house finishing can streamline work flow and lower inventory levels, thereby freeing up capital for other uses. The ability to finish parts in-house also enables shops to machine the part, finish it and move immediately to assembly or shipping. “Manufacturers can focus on part fabrication—the highest value contribution—then quickly and efficiently handle black-oxide finishing without disrupting the smooth flow of parts through assembly, packaging and shipping,” he explained. 

Cs Birchwood Casey.tif

Courtesy of Birchwood Casey

Birchwood’s Tru Temp low-temperature, black-oxide process contains no EPA-regulated metals and reportedly provides a durable, corrosion-resistant finish that doesn’t alter part dimensions or interfere with assembly or operation.

Black oxide produces a durable, corrosion-resistant finish that adds value to many fabricated parts without altering dimensions or interfering with part assembly or operation, according to Birchwood Casey. The process’ low temperature reportedly eliminates the energy costs and operator hazards of hot-oxide processes, making it safe and relatively easy to operate in-house. Like other finishing processes, it involves multiple tanks: ones for cleaning, surface conditioning, blackening and sealing, with rinse tanks between each process stage.

“Potential users of in-house blackening should consider the volume of parts to be finished per shift, handling method required, the need for cleaning parts that are heavily contaminated with oils or scale and the performance requirements of the final finish,” Ruhland said.

The company supplies systems for low-temperature blackening, including all tankage, process chemicals and training. Its latest products include a CNC blackening system that automates the process for higher volumes and a blackening process for aluminum parts that is said to provide an alternative to black anodizing.

According to Ruhland, Lumiclad is a 30-minute process that creates a smooth, electrically conductive coating on aluminum alloy parts. Coating thickness is 0.000060" (1.5µm), and the coating has good adhesion, he added.

“Lumiclad is an ideal finish for precision machined components with critical dimensions or for mating surfaces that require break-in lubricity and galling resistance,” Ruhland said. “It has a uniform thickness that will not close down hole diameters or change critical part dimensions, and its inherent lubricity make it an ideal choice for sliding wear applications.”

The patent-pending process has a slightly porous structure that absorbs an optional topcoat, such as clear polymer, light oil or dry-to-touch sealant, Ruhland noted. The resulting finish is well suited for fixtures, sliding assemblies, electronic subframes and decorative surfaces. CTE

About the Author: Jim Destefani, a contributing editor for CTE, has written extensively about various manufacturing technologies. Contact him by e-mail at jdstef2001@yahoo.com.

Contributors

Birchwood Casey 
(800) 328-6156
www.birchwoodcasey.com

Briney Tooling Systems
(800) 752-8035
www.brineytooling.com

KC Jones Plating Co.
(248) 399-8500
www.kcjplating.com