A groovy new quick-change cutter

Tried and true snap rings make bushing retention a snap.

Ingersoll Cutting Tools (Rockford, IL) has commercialized a special toolkit based on a time- and cost-cutting bushing retention idea originally thought up by some savvy Midwestern moldmakers, an idea that reportedly saves machining and assembly time, while at the same time strengthening molds. The moldmakers asked themselves, "Why use socket-head screws to secure ejector and guide pin bushings? Why not use snap rings? Yeah, why not? We could just machine a snap ring groove in the counterbore for the bushing’s lip, insert the bushing, and snap it in the retaining ring. Yeah . . .

"There would be just one machine step, one done on the same centerline as the bushing bore itself . . . no measuring, no offsetting. Yeah . . ."

When the folks at Ingersoll heard about it, they said "Yeah," too. But they added, "With the right toolkit, there’d be no need for tool changing or machine repositioning, either.""The new practice should save U.S. moldmakers millions of dollars a year in machining and assembly time," says Chad Meyer, the Ingersoll application engineer who helped develop the toolkit.

Yeah . . . sounds like a plan.

Ancient History

The old way was much more tedious and tricky. It took about four times as long for each bushing and involved drilling, counterboring, tapping a screw hole just at the edge of the bushing counterbore, and then threading in a screw. The underside of the screw head engaged the top of the bushing to secure it. Locating that retaining screw was tricky. The offset had to be radially accurate or the screw’s underside wouldn’t catch enough of the edge of the bushing lip to secure it.

Also, the screw had to be in the right place on its offset circle, or it could interfere with the moldset’s assembly and operation.

The Midwestern moldmaker who pioneered the development of the new method used to machine the grooves with a four-flute, high-speed steel grooving tool after completing the bushing counterbore. Cutting the slot was faster than opening the screw hole, but it still left room for improvement.

Although the spindle and mold block remained in position in the x, y, and z directions for both operations, changing from the boring tool to the groove slotter still took time. Sometimes it also involved raising the spindle, or lowering the table to make room for the exchange.

And, making the actual cut was slow going. They didn’t want to overload and deflect the cutter with lateral forces. That’s when Ingersoll’s Meyer came to the rescue.

Cutting Time

Meyer saw that the two operations were coaxial. He suggested switching to an Ingersoll Chipsurfer tool, which features interchangeable tips on a common shank.

All the moldmaker had to do was bore the bushing hole, counterbore with a boring tool, and then change to a grooving tip for the snap ring groove—all with the spindle, table, and tool shank in the same position. Cutting the groove then became a simple matter of making an orbiting cut.

Since everything is left in place, and since the interchangeable Chipsurfer tips hold both axial and radial positional repeatability to within ±.0005 inch, the snap ring groove location accuracy is as sure as death and taxes.

The mold shop tried it and reportedly has found that tool changes average 10 to 15 seconds. Actual machining of the slot took 12 seconds—half the time it used to take. They ran with depths of cut up to 1/8 inch in a 1¾-inch bore. Other mold shops nearby heard about it, got on board, and reportedly have enjoyed similar results.

Stronger Molds

Ingersoll calls its new toolset the Kit-Pak. Each Kit-Pak contains four slotters with widths of .056, .068, .086, and .125 inch, covering the four most common slot sizes. Each grooving tool features six flutes. No sweat. Molders more familiar with the old four-flute HSS slotters report a doubling of cutting rates with the Chipsurfers.

The cutters are carbide and the 3/8-inch shank is in tough high-speed steel. When the cutters go dull, they can be replaced rather than reground. It’s cheaper.

OK, but what about making molds more robust, you ask? Ingersoll sources tell us their customers say that forces are more uniformly distributed around the ring, instead of being concentrated on just one point of the bushing lip. They add that mold servicing goes faster, too.