Quick-change-jaw systems for chucks offer multiple benefits

To compete, high-mix, low-volume parts manufacturers are well-aware that they need to spend as much time as possible in the cut rather than setting up. Chucks with quick-change jaws let them do just that.

In addition, quick-change jaws help shops overcome the skills gap, according to Steve Hartung, group product manager for rotational workholding at SCHUNK Inc., Morrisville, N.C. Shops can easily train less-skilled operators to quickly and accurately change a chuck’s soft jaws, also known as top tooling or inserts, via a simple-to-use tool and, in many cases, avoid having to rebore the jaws.

For example, Hartung said the SCHUNK PRONTO quick-change-jaw system (shown) only requires an operator to turn a T-wrench 90° to remove an insert and turn another 90° in the opposite direction to install a new insert for a new job. The process consumes about 5 seconds per jaw and provides a repeatability of 25µm (0.00098″). And to further enhance productivity, a robot can easily be programmed to swap the PRONTO inserts.

“That’s another advantage of the system,” he said.

Saving Time and Money

Moreover, reducing the time it takes to change the workholding setup on a chuck from one job to the next provides a fast return on investment for a quick-change chuck jaw, which has a higher acquisition cost than a standard soft top jaw.

A quick-change-jaw chuck with fixture from Pratt Burnerd America. Image courtesy of Pratt Burnerd America.

Lee Chase, CEO of QCS Workholding LLC, Houston, said the nominal setup time for a proficient worker to change standard jaws is 15 to 20 minutes. The process typically involves breaking the bolts, finding the required jaws, removing the jaws from the previous job and replacing them with the ones for the new job. “And usually, for accuracy, you’re going to have to rebore them,” he added.

Chase knows the process well because he ran a lathe when the company started as a job shop. “About the fourth time we changed our standard jaws in a day, I said, ‘There’s got to be a better way,'” Chase recalled. “The next day, the owner had the first prototype made.”

In contrast to changing standard jaws, a jaw change takes 10 seconds with QCS’ J-LOC quick-change chuck jaw when the master jaws are on a chuck, Chase said. To show the cost savings that the reduced setup time can achieve, the company provides a cost comparison between standard soft jaws and J-LOC C-style quick-change jaws mounted on a 10″ (254mm) 3-jaw Kitagawa chuck. (Visit tinyurl.com/ydz8auww.) The comparison shows the cost of acquiring 10 sets of standard soft jaws ($630) versus one set of J-LOC quick-change chuck jaws ($780) and 10 sets of J-LOC quick-change inserts ($1,350), or $1,500 more.

However, according to the company, the estimated cost for 10 repeated usages of 10 sets of standard soft jaws is $5,630 compared with the estimated cost of $2,737 for 10 repeated usages of 10 sets of the quick-change inserts—a savings of $2,893.

Chase explained that the company’s inserts, which are made of mild steel, are bored like soft jaws. After a shop initially bores the inserts, they are placed back on the master jaws for repeat jobs, the program is changed and the job is run. To achieve a repeatability of 0.0005″ (12.7µm), an insert must be placed back on the same master jaw it was bored on, which requires properly numbering the master jaws and their inserts.

A J-LOC C-style quick-change chuck jaw from QCS Workholding. Image courtesy of QCS Workholding.

“You just take your standard jaws off and replace them with our master jaws,” Chase said. “Theoretically, you don’t ever want to remove the master jaws once you bolt them on. All your adaptation is done with the inserts.”

To make the inserts more economical, they are reversible, he added. “You can bore each end of a set of inserts for a different diameter.”

Force Factor

It’s important that the chuck maintains as much jaw force as possible at the lathe’s maximum speed.