Chuck aids retention knob work

END USER: JM Performance Products Inc., (800) 322-7750, www.jmperformanceproducts.com.
CHALLENGE: Enhance precision and shorten changeover time when machining retention knobs.
SOLUTION: Quick-change collet chucks.
SOLUTION PROVIDER: Hainbuch America Corp., (800) 281-5734, www.hainbuchamerica.com.

Competitive manufacturers continually seek new and innovative ways to improve product quality while cutting costs, and a logical starting point involves methods to increase tool life.

JM Performance Products Inc., Fairport Harbor, Ohio, offers a retention knob that has quickly gained acceptance as a means of extending tool life and improving tool performance. The company, which started as the job shop J&M Machine in 1966, developed a high-torque retention knob that prevents the toolholder taper from expanding, thereby reducing the harmonics responsible for premature tool failure.

“In conventional milling machine operations, 70 percent of the toolholder taper does not contact the spindle,” explained Andrew Rowley, president of JM Performance Products. “This results in an uneven wear pattern capable of causing tolerance problems, as well as (negatively) impacting the tool. The spindle opens and the expanded toolholder becomes lodged, creating the characteristic ‘thump’ frequently heard during tool change. Our design stops the toolholder from expanding so it does not become lodged.”

Since production of the retention knobs began 5 years ago, the line has grown to encompass about 400 different versions for virtually every type of toolholder. The variety offered continues to expand and currently ranges from ¾ ” (19.05mm) for a 30 taper holder to 2¾ ” (69.85mm) for a 60 taper holder, with a maximum length of 45⁄8 ” (117.48mm) for the 60 taper holder, machined from 2¾ “-dia. stock.

The knobs are made from 9310 tool steel or 8620 steel. Plant Manager Craig Fischer noted that 9310 has a higher chromium content and is about 40 percent stronger than 8620. “Everything will eventually be made out of 9310,” he said. The knobs are heat treated and shot peened to enhance rigidity, and most are equipped with coolant holes.

As the number of configurations grew, so did the need for faster changeover times and improved manufacturing capability to maintain precision when cutting materials with a hardness up to 225 HB. This led to a search for better workholding methods.

The company was using 3-jaw chucks with soft jaws, but the workpieces would cause the jaws to wear and reboring the jaws took up about 20 minutes every day—sometimes every 12 hours, Fischer said. “And that’s if you got it right. It took a good setup guy to get the jaws bored right.”

In addition, the company experienced pushback, where the bar stock slides in the collet during machining, when running at the toolmaker’s recommended speeds and feeds. “I couldn’t compensate because sometimes it would slide back 0.050 ” and sometimes it would slide back 0.100 “. I don’t have that type of tolerancing in my parts,” Fischer said.