Retention knob reduces polishing

END USER: Briney Tooling Systems, (800) 752-8035, www.brineytooling.com.SOLUTION PROVIDER: JM Performance Products Inc., (800) 322-7750, www.jmperformanceproducts.com.CHALLENGE: Reduce post-machining polishing time.SOLUTION: Tooling toolholder assemblies with high-torque retention knobs.

Briney Tooling Systems is well-known as a toolholder manufacturer, but the Bad Axe, Mich.-based company also has a sister facility that performs job shop work. The shop often machines workpiece materials hardened to 50 HRC or harder and manually polishes the parts after machining to achieve the required surface-finish specifications, noted Justin London, sales engineer for Briney.

One such job involved producing punches made of H-13 tool steel hardened to 50 to 55 HRC that had a complex profile on one end. London said each punch required 1 to 2 hours of manual polishing using angle-head pneumatic tools to impart the specified 8-rms finish. In addition, workers had difficulty achieving a consistent surface finish.

A toolholder from Briney Tooling Systems is tooled with a high-torque retention knob from JM Performance Products. Image courtesy Briney Tooling Systems.

JM Performance Products Inc., Fairport Harbor, Ohio, then informed Briney about its high-torque retention knobs. According to JM Performance Products, a conventional retention knob, when installed in a toolholder, will deform the precision taper because of the elastic nature of a toolholder’s thin walls. This taper deformation prevents a toolholder from properly mating with the spindle of a CNC machine. When the toolholder expands, taper contact can be reduced by as much as 70 percent. When properly installed with a retention knob socket and torque wrench, the patent-pending design of the high-torque retention knobs prevents toolholder deformation.

London concurred that a conventional retention knob changes the taper form of a toolholder and creates a permanent deformation that, however small, negatively impacts machining performance, toolholder rigidity and tool and spindle life. “We have done our own internal study and found torque on toolholders as low as 15 ft.-lbs. could cause warpage,” he said.

Briney switched to the high-torque knob and ran the program, London said. “At first it didn’t visually look like there was much of a difference.” However, it only required 15 minutes or less of polishing to impart the required surface finish rather than 60 to 120 minutes.

In another application on the same machining center, polishing time to achieve an 8-rms finish went from 28 to 2 minutes for a part made of YXR-33 HSS hardened to 50 HRC after switching to the high-torque retention knob. Again, London pointed out that the shop did not see the difference the knob made until an operator began to hand polish the part. “This reason alone was enough to switch over all of our milling centers to high-torque retention knobs,” he said.

After realizing the benefits the high-torque retention knobs from JM Performance Products had on its job shop applications, Briney began offering those knobs with the toolholders it produces, as well as JM’s standard retention knobs. The company stated that its standard knobs, for example, have radius thread points to help increase knob strength.

London noted Briney sells about 15 to 25 percent of its toolholders with a high-torque retention knob, and expects the percentage to increase as more end users begin to understand the knob’s critical role as the interface between the toolholder and machine spindle. “They are moving towards the high-torque knob so they can minimize the expansion that happens at the small end of the taper when they over-torque it,” he said.

The price premium for the high-torque version is about 10 to 20 percent, depending on the type of knob, London added. JM manufactures BT-, DIN-, ISO- and CAT-style knobs in sizes from 30 to 60 taper.

“It’s a very small investment to protect equipment that you spent hundreds of thousands of dollars on,” London added.