Shop taps into learning by fabricating science center exhibits

Figure 1
This ball range—which C.W. Shaw manufactured for a Fort Lauderdale, Fla., science center using ¼-in.-wall, 4-in. square 304 tubing—required 1,000 holes

Situation

More than many machinists, Charlie Shaw can arguably reason that his work helps make happy, smart children. Shaw is the president of C.W. Shaw, a St. Petersburg, Fla.-based fabrication shop for science center exhibits. Shaw and his team manufacture the larger-than-life contraptions that children of all ages crank, turn, pull, and press while subtly learning about problem-solving, math, and natural science.

Seeing photos of children learning and laughing while using his products is rewarding, especially since he knows that machining those exhibits is no laughing matter. From concept to construction and installation, C.W. Shaw handles the fabrication, millwork, metalwork, and electronics of large-scale exhibit projects.

Shaw has a machine shop and CNC machine center on-site and a considerable array of tools—he never knows what unique demands the next project will bring. Two years ago an addition to the tool bench streamlined how Shaw taps holes in stainless steel, a very common material used to fabricate most exhibits that come through the shop.

The project was an outdoor ball range for a science center in Fort Lauderdale, Fla. (see Figure 1). Visitors to the exhibit experiment with force and trajectory in two ways: creating air pressure through a plunger and aiming and shooting balls through a nozzle at targets. At 50 ft. long, the sizable length of the range encourages participants to use teamwork as they help the shooter adjust to get balls through the hoops.

The project was straightforward, and Shaw had already built a similar exhibit for a museum in Pasadena, Calif. The California model, engineered to withstand an earthquake, is made of 11-ga., 1-in. square 304 stainless steel tubing. The project required more than 1,000 ¼-in. holes, which Shaw’s crew tapped by hand with a cordless drill—laborious, to be sure, but not out of the norm for the shop.

The Fort Lauderdale model, however, needed to be built to withstand 156-MPH winds, the top speed of a Category 4 hurricane. Shaw’s engineers designed the model with ¼-in.-wall, 4-in. square 304 tubing. Suddenly the 1,000 holes posed a problem: a cordless drill would surely break multiple taps, and that could cause the tapped piece to be scrapped.

Scrapping a piece of material already worth $500 and which took hours of machining to produce because the operator broke a bit while tapping the thousandth hole is a waste of money, material, and production time.

Resolution

Shaw spent some time on the internet doing research and found FlexArm Inc., a manufacturer of hydraulic and pneumatic tapping arm systems. Shaw suspected a mounted tapping arm could handle the project, so he purchased a GH-18 electric tapping arm with a tilt head and steel stand.

Figure 2
This bed of nails project, designed to teach children about pressure distribution, required C.W. Shaw to tap 4,000 holes.

The tapping arm has a 110-V green power motor with #6-5/8-in. tap capacity.

Its adjustable gas counterbalanced springs allow the operator to position the tap over a hole without straining or fatigue. The tool absorbs the torque created by the motor to help increase tap accuracy.

An adjustable-torque clutch allows the tap to stop turning when it encounters any obstruction that might cause breakage, reducing the likelihood of breaking a tap. According to the manufacturer, the unit typically produces more than 3,000 holes without breaking a tap.

But tapping ¼-in. holes in 1/8-in. steel is a lot easier than tapping ¼-in. holes in ¼-in. material. When the aspect ratio approaches 1-to-1, the likelihood of breaking a tap skyrockets, particularly in 304-grade stainless steel, Shaw explained. When the material is closer to ½ in., a tapping arm or electrical discharge machining unit would be required just to get the broken taps out. But even after the thousandth hole, the FlexArm didn’t break a single tap, and the $500 components were saved from the scrap heap. As a result, Shaw’s tapping arm paid for itself in the first job.

While some pieces are still best tapped in the vertical machining center, Shaw found an unexpected use for the tapping arm in pieces that don’t fit in the machining center or pieces that demand exacting precision. He was pleasantly surprised how easy it was to tap holes in his welding table for special fixtures.

There’s no doubt Charlie Shaw has a fun job. He and his team build exhibits that capture children’s imaginations and sense of fun, while subtly teaching them skills and facts about the natural world. When it comes down to machining some of those exhibits, the job gets a little less fun. Broken taps that scrap expensive material and cause costly production downtime are a buzz kill. The tapping arm has put a little of the fun back into production by decreasing the likelihood of tap breakage and making the tapping process easy and efficient.

Shaw doesn’t use the unit on every project that comes into his shop, since projects change so drastically from one to the next. For large-scale projects, or projects that demand precision, the tapping arm has allowed Shaw to bid with more confidence, rather than being concerned about one broken tap sucking all the profit out of a project—which can suck all the fun out of the job. On a recent project that involved more than 4,000 holes for a bed of nails designed to teach children about pressure distribution (see Figure 2), the unit helped make production a little less like … well, lying on a bed of nails.

FlexArm Inc. www.flexarminc.com