Boring, drilling for aerospace and job shop.

Whether producing "one offs" or parts in production runs, precision cutting tools that can meet critical tolerances are required, ensuring the quality of performance-critical parts. In the case of NASA's Mars Exploration Program, two "one-off" (the twin rovers: Spirit and Opportunity) depended on decidedly earth-based boring tools from BIG Kaiser to bore holes in the titanium structure of the spacecraft lander.

By now, the twin rovers' exploits on the Martian surface have dramatically whetted the appetites of earth-bound scientists for still more data. The long-term effort of robotic exploration with the goal of unraveling the secrets of the red planet's past environments, the history of its rocks, the many roles of water, and, possibly, evidence of past or present life is well kinder way.

The preparation leading up to the successful mission involved precision metalworking processes as shown in the machining of the spacecraft lander, the protective "shell" that houses the rover and protects it from the forces of impact. The lander is a strong, lightweight structure, consisting of a base and three sides in a pyramid shape. In effect, each rover is time mechanical equivalent of a geologist walking the surface of Mars.

Precision holemaking

Several 0.826" diameter holes had to be bored in the titanium structure of the lander to accept a most critical component of the landing vehicle. The depth of the bore was 0.300" with a reach of 1.3" through a tool plate. The bore tolerance was [+ or -] 0.000050" (just over 1 micron). To fail and scrap the expensive lander structure was not an option. The machine tool available was a horizontal boring machine with CAT 50 spindle.

Members of the JPL machine shop team and Ed Schenk, BIG Kaiser application engineer, developed the process and selected the boring tools for the job, a KPT 112.116 precision boring head with a short projection carbide bar and standard insert for titanium machining. The trial bores allowed some fine-tuning of time machining parameters and when time bores showed consistent results within the required tight tolerance band, the process was approved and the actual holes success fully bored.

In a more earthly application, K&A Machine, Jackson, MI, solved a problem for a customer in drilling holes in connecting rods used in a major manufacturer's refrigeration and cooling compressors.

"We were having trouble meeting the customer's production demands of 50 parts per shift," explains Jim Hitt, operations manager. Both the customer and the job were new for K&A.

The operation begins with a cored pocket on each side of time pin end of a connecting rod. K&A and its customer had been using a spade drill in a pecking process to drill the hole. It required 18 pecks to complete the difficult interrupted cut required for each part.

BIG Kaiser representative John Kaplinski of H&N Associates Inc., Jackson, MI, proposed dispensing with the pecking operation and using Kaiser's durable indexable insert drill. Unlike the spade drill, the indexable insert drill is not so sensitive to interrupted cutting and does not need the pecking cycle.

Now K&A uses a Kaiser indexable drill for the job, saving 1.0 minute on each of 25,000 parts or 416 hours annually, says Hitt. "We had to hold a certain size, and the indexable drill brings it right to size on the first pass," he says.

"With the Kaiser boring heads and the indexable insert drill, we are doing 55 parts per shift," says Hill. "The customer is pleased, and we are ecstatic." Total annual savings from the process improvement come to nearly $50,000.

The Kaiser indexable insert drill, 10.336.012, will produce a drilled hole of diameter 1.094" when used in a standard KAB shank on center. In this case, however, it was important for the finishing processes that would follow that the drilled hole be cut to a large size, but still smaller than the next drill of 1.125" diameter. Kaiser indexable drills can be used off-centerline, and when used in this way, they will produce drilled holes tip to +0.040" diameter from nominal size.

Using the indexable drill off-centerline saves the cost and lead time that would be required to make a special diameter drill. The KAB6 connection of the adjustable drill holder has an eccentric built in, which, when rotated, will move the centerline position to any specific size in increments of 0.004"/diameter, which can be split for 0.002"/diameter.

Using a Kaiser 10.336.012 indexable drill with 11.658.644 carbide insert, a CAT 40 adjustable drill holder 11.336.311 and the KAB6 connection, K&A adjusted the standard 1.094" diameter to more than 1.10" diameter. Drill depth is 1.437" in ductile cast iron.

The tool ran at 500 sfm (1,736 rpm) and a feedrate of 0.006"/rev (10.4 ipm).

Kaiser TWN twin cutters were used for rough boring and balanceable finish boring head 10.112.117 for both pin and crank bores, using different insert holders and balancing for each component assembly and diameter separately.

Founded in 1980, K&A Machine currently operates a 12,000- square-fool plant with a planned 8,000-square-foot expansion. Its equipment includes Haas Automation machining centers and Mazak turning and milling centers. It specializes in short to medium run jobs and accepts mostly aerospace jobs with tight tolerances. BIG Kaiser, www.rsleads.com/ 406tp-224