Quick connection: Drilling Performance

Making a simple-looking part sometimes requires a complex series of operations. That was the case when Falcone Precision Machine Inc. had to produce 8,000 pieces of a 0.916 “-long × 0.247 “-wide × 0.056 “-thick electrical connector made of Kovar, an iron-nickel-cobalt alloy. True position for a series of 18 holes in the connector was to within 0.002 ” of the holes’ centerlines, and specifications required part edges to be sharp with no burrs. The parts had to be burr-free because the customer intended to fill some of the holes with glass and set in 0.018 “-dia. wires and gold-plate the entire connector to enhance conductivity.

Falcone Precision Machine created a workholding setup and machining processes to maximize productivity, repeatability and economy in producing 8,000 of these electrical connector components.

Falcone Precision, Latrobe, Pa., created a workholding setup to maximize productivity, repeatability and efficiency. In one vise on the table of a Fadal 3016 vertical machining center, a 6 “×⅜ “× 0.l00 ” Kovar blank was clamped for machining of one side of the connector. A second vise had fixtures to hold five connectors cut from the blank after machining the first side.

According to Mark Falcone, co-owner of the shop with his brother, Kevin, the part thickness dictated that the parts be cut apart for the operations in the second vise. “Otherwise, if you turned the blank over and put it in the second vise, you couldn’t keep it flat enough,” he said.

In the first operation in vise No. 1, an Atrax ¼ “-dia., square-shoulder, TiAlN-coated carbide endmill run at 6,000 rpm and a 36-ipm feed rate roughed the perimeters of five parts and facemilled the tops. Then the same endmill moved to the second fixture and roughed the second side’s perimeters of the then-separated parts. Next, an identical but fresh ¼ “-dia. endmill finished the top and perimeter of the parts in the first vise and finished the parts in the second vise.

Those parts already featured holes created on vise No. 1. There, 18 hole positions were spotted with a 0.046 “-dia. center drill run at 7,300 rpm and 3 ipm. Twelve of the spots, for through-holes, were 0.010 ” deep, “If you went too far, then the drill would chamfer the hole too much,” said Kevin. The six remaining hole positions were to receive a 0.070 “-dia., 0.004 “- to 0.007 “-deep spotface with a 0.028 “-dia., 0.020 “-deep counterbore in its center. Those six locations were spot drilled to a depth of 0.020 “. “If we didn’t go to that depth, the 0.028 “-dia. endmill we used to make the counterbore would break because it was just plunging straight down,” Kevin said.

The through-holes were drilled with a 0.062 “-dia. cobalt drill run at 5,000 rpm and 2 ipm. When through-drilling was completed, an M01 command stopped the program to enable visual verification that the tool wasn’t broken. “That’s how high maintenance the part was,” Mark said. “We had to watch for broken tooling on every run.”