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Deburring/Finishing

Right tool for the job

By Nick Wright

Tool manufacturer saves time and salvages parts with a versatile grinding machine

November 2012 - With virtually all metal fabrication, finishing is an integral part of the job. Whether it’s for surface preparation, polishing or deburring a rough edge, fabricators need to be confident their parts are ready to move on to further processing or customer delivery. For the latter, cosmetic condition is equally important for the top dollar customers pay for top-shelf products.

At L.S. Starrett Co., Athol, Mass., the difference between shipping a finished product and scrapping it completely hinges on its ability to add a grain finish quickly and consistently on its firm joint calipers. Calipers are one of the myriad metrology and measuring devices for assessing material thickness that Starrett manufactures and sells via catalog. The company is also known for its high-performance band saw blades and other tools.

Firm joint calipers are simple devices. With minimal hardware, they measure distances from one point to another with great reliability and accuracy; for example, the outside diameters of tube, pipe or other construction materials. 

ffj-1112-deburring-image1Starrett’s firm joint calipers, manufactured from steel, leave the warehouse with an induced grain finish to give them a consistent appearance, according to Laurence Perry, chief engineer at Starrett. Occasionally during material handling or assembly of certain caliper arms, which can be from 1 ft. to about 3 ft. long, unintended scratches, blemishes or dings can occur. While not necessarily compromising the integrity of the caliper’s basic measuring function, Starrett’s customers won’t accept anything short of a perfect product—the car on the lot with a hairline scratch will still run, but not likely sell.

“Quality is important to our customers,” says Perry. “If there’s an imperfection, the customer will pick up on it and it’s not acceptable.”

To achieve the required finish for blemishes that would otherwise render calipers as rejections, Starrett turned to the Multi-Max machine made by CS Unitec, Norwalk, Conn. The Multi-Max is a stationary multipurpose grinder intended for both linear and rotary finishing and blending operations. CS Unitec is a manufacturer of portable power tools with a specialized product line for deburring and finishing.

Reducing labor

Before Starrett sourced the Multi-Max grinder, the company’s operators would buff out any scratches by hand—a time-consuming endeavor that, if it didn’t remedy the finish, would result in the part being scrapped. It could take a worker a half hour or more to rework a part, whereas the Multi-Max can do it in a matter of minutes or less.

“The reduction in scrap is the biggest benefit because we don’t have to scrap the part,” Perry explains. “Salvaging those parts is the biggest difference in our operation.”

Production of the calipers entails either shearing or laser cutting free machining steel, usually C1010 cold-rolled sheet with a No. 1 temper, following a straightening operation depending on the specific caliper. For example, on some of the longer calipers, 24 in. to 36 in., Starrett runs the arms through an abrasive belt to create a grain finish. Edges then get polished. After the arms are bent and straightened to a half-moon shape, the calipers are assembled and tested to ensure the tips touch each other instead of “going astray,” Perry says. The half-moon shape makes it particularly tricky to finish the contoured shape.

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 While scratch removal is not a regular occurrence, it’s part and parcel of production. If a small scratch appears across the radius of the caliper arm that doesn’t match the rest of the piece, the operators at Starrett turn to the Multi-Max.

The machine features two spindles that protrude from opposite sides, effectively giving operators two shaft mounting options from one motor. The 5⁄8-in. 11 UNC mounting shafts accommodate CS Unitec’s full range of PTX abrasive wheels on one side and FIX discs in diameters from 4 in. to 7 in. on the other side. It runs on 220 V three-phase power with a top speed of 2,800 rpm, according to CS Unitec. It can be mounted to a bench or other surface for stability. Starrett has its Multi-Max secured to a 2-ft. by 3-ft. bench that operators can move around the shop as needed.

“It’s totally portable,” says Perry, noting that Starrett bought its Multi-Max in March this year.

Starrett’s manufacturing facility is about 450,000 sq. ft., of which approximately 3,150 sq. ft. is dedicated to its finishing department.

Because a fully expanded 3-ft. caliper becomes 6 ft. long, Starrett has provided room to maneuver parts to the Multi-Max.

“That’s the good part about the machine, we just use the top of the wheel,” Perry adds. “With the flip of a switch, the operator can see what he’s doing and just pulls the part along the top of the wheel against the rotation to lay a grain lengthwise.”

With two spindles, Starrett can rough out a scratch with CS Unitec’s 60-grit flap wheel, then turn to the obverse spindle equipped with a 180-grit fleece wheel to finish up. 

“The flap wheel takes out all the scratches and imperfections we’re looking to remove, and the fleece wheel lays a nice grain,” he says.

 

FFJ-1112-deburring-image3

Switching out consumables is easy as well, says Scott Saunders, technical sales representative at CS Unitec. With the FIX Hook and Loop system, a Velcro-like disc mounting system for quick consumable changes, operators can quickly swap discs without tools (CS Unitec’s discs and wheels are compatible with all of its deburring and polishing tools). This makes the finishing process faster for fabricators, saving precious time.

“They can slide the whole part through the Multi-Max in a matter of seconds and create a consistent finish across the board,” Saunders adds.

Linear plus rotary

The Multi-Max’s two spindles capture the multi-dimensional forms of finishing underlying CS Unitec’s products: linear and rotary. This is effective for smaller parts that can be manipulated by hand, says Saunders.

When using a handheld linear or rotary  blending tool, operators are taking the tool to the workpiece. That’s appropriate for larger pieces such as sheet metal or larger fabricated parts. But for smaller components, like Starrett’s calipers, it isn’t possible to bring the tool to the workpiece.

“The Multi-Max system allows for one side of the machine to be used as a linear finishing tool and the other side as a rotary finishing tool,” says Saunders. “So you have the best of both worlds in one stationary, multipurpose tool.”

The Multi-Max also can be equipped with a flexible drive shaft, which allows operators to blend and polish tight and hard-to-reach spots. With this feature, operators can essentially add another complete dimension to the Multi-Max.

Perry says that since Starrett began using the Multi-Max, he and his shop foreman are no longer burdened by the prospect of minor scratching rendering salvageable parts useless.

“Those parts are pretty expensive,” says Saunders. Some of Starrett’s larger calipers can cost hundreds of dollars. “Starrett can get a consistent quick finish, and their workers aren’t complaining of a sore wrist.”

While the Multi-Max is used on an as-needed basis, it’s become an indispensable complement to Starrett’s finishing process.

“Time is money in finishing,” says Saunders. “In a fabrication shop, if the estimation on the finishing time isn’t accurate, then the majority of profit for the whole job can be lost. Having a Multi-Max in the shop has helped increase both production and the profitability for several companies.” FFJ

Interested in purchasing reprints of this article? Click here

Sources

  • CS Unitec
    Norwalk, Conn.
    phone: 800/700-5919
    fax: 203/853-9921
    www.csunitec.com
  • The L.S. Starrett Co.
    Athol, Mass.
    phone: 978/249-3551
    fax: 978/249-8495
    www.starrett.com


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