Grinding it out: No job is too big or small for 548th PMXS Machine Shop Published Oct. 2, 2015 By Kimberly Woodruff Staff Writer TINKER AIR FORCE BASE, Okla. -- Deep in the recesses of Bldg. 3001 sits a shop that works on the intricate parts that make up aircraft engines. Dan Sharp, supervisor with the 548th Propulsion Maintenance Squadron Machine Shop, said the shop keeps busy with big and small jobs coming through. "The smaller jobs aren't as glamorous," he said, "but they're no less important to the mission." For the last 25 years, the Machine Shop has been home to Big Blue, a large blade tip grinder, used primarily to finish grind blade tips on jet engine turbine motors. Mr. Sharp said Tinker used to be the only place in the Air Force with the machine, but now there are some others. With Big Blue, a precision laser accurately measures each blade tip under the rotational load. After the grinding, a felt brush is used to remove the burrs. It takes about six hours to rough grind, brush and finish grind. Mr. Sharp said there are only three people at Tinker who are authorized to run Big Blue. The newest one being Chris Cunningham, who has been with Blue for the past five months and is "good at what he does," said Mr. Sharp. Mr. Sharp said that once a month a master part is brought in to compare the precision dimensions. "Big Blue is kept pretty busy. It runs quite often up to 12 hours a day," said Mr. Sharp. Big Blue isn't the only power horse machine in the shop, however. According to Mr. Sharp, Tinker AFB is the only base that uses spark erosion machining. In spark erosion machining, a desired shape is obtained using electrical discharges, such as the case when cutting a honeycomb as part of the inside duct airflow system. The F-119 engine cooling duct is a honeycomb design that allows for only so much air to flow through the engine. Material is removed from the work piece by using rapid current discharges between two electrodes separated by dielectric liquid or a coolant of sorts. Another thing Tinker does that no one else does is grooving using the vertical turning center. "We can cut a groove so the other parts can catch and hang on," Mr. Sharp said. "The groove holds it in place." The VTC also mills, drills, turns parts and cuts metal with a carbine insert tool. Of course, Mr. Sharp said not everything in the machine shop is automated. Some of the work is done the old fashioned way -- skilled handiwork. "My guys are a great group of guys -- not only in the shop and the work they do, but they're also great people to know," said Mr. Sharp.