Keeping concentric: General Industry Coverage

Shrink-fit toolholders minimize runout to no more than 0.0002 ” and, as a result, extend tool life, provide a consistent chip load and enable the cutting tool to impart a fine surface finish. But if a part manufacturer using thermal-grip holders doesn’t have through-coolant cutting tools and has to use external coolant, the coolant does not effectively reach the tool/workpiece interface where it’s needed, according to Timothy Fara, managing director for Bilz Tool Co. Inc.

Therefore, the manufacturer of tool clamping systems developed the JetSleeve coolant delivery system, which is comprised of a shrink-fit chuck encompassed by an aluminum sleeve, or housing. Coolant pressure is created within the sleeve and delivered to the cutting edge via coolant holes in the face of the gold-colored sleeve.

Initially, Bilz equally spaced 16 coolant channels around the holder face, made all the holes for the channels the same diameter and positioned them on one bolt circle, and directed the coolant at the same angle, Fara noted. This design caused the coolant to be applied at the same point for every tool, regardless of whether the tool, for example, extended 1 ” or 6 ” from the holder. “Therefore, coolant wasn’t necessarily getting down to the cutting tip,” Fara said, “and centrifugal force was pulling the coolant away.”

Courtesy of Bilz Tool

Bilz Tool reports that its JetSleeve through-coolant, shrink-fit chuck reduces coolant consumption by up to 70 percent.

In addition, putting coolant holes through the holder body or coolant grooves along its ID changes the concentric expansion and contraction of the bore, Fara pointed out. “Those holes or grooves create voids and change the heat path, so the holder tends to open and close elliptically,” he said. “That means you’re not gripping your tool with the full force 360° around the shank.”