As parts and materials have advanced, tools and methods that were once standard have been replaced by better, more advanced technologies. It is important to recognize the advancements essential to your operation.
An example of this can be found in workholding for rotational parts. For more than a century, the standard implement has been the three-jaw chuck. Most likely, your CNC machine came equipped with one. Most machinists train with three-jaw chucks and, because it is all they have ever used, they are comfortable with them. Even today, when it comes to the production of a large quantity of parts that do not require a high degree of precision or concentricity, the three-jaw chuck is an excellent tool—provided that it is well-tuned and not worn.
These chucks work well for general tolerance machining in the 0.001-0.005" (0.025-0.127 mm) range of parts that vary in size from 0.5-7.5" (12.7-190.5 mm) in diameter. They also work well for clamping on raw cast or forged parts.
Advanced Machining Needs More
With more improved materials, more complex parts and faster cycle times, a better workholding system is vital. The quick-change collet chuck delivers superior performance on all fronts.
Brian Zimdars, a CNC machinist for Hainbuch America Corp., Germantown, Wis., said: “When I was in training more than 30 years ago, the only workholding option for turning was three-jaw chucks. Ten years ago, when I was introduced to the quick-change collet chuck, I was hesitant—perhaps even a little unwilling—to make the change.”
He quickly recognized the many advantages of the quick-change collet chuck. He found they are a fast, efficient way to change over when machining various stock sizes. The greatest advantage for machinists is the fact that they have an infinite amount of end-stop positions. There is no need to bore new jaws with every use.
“You no longer need to worry about what jaw size you have to switch to, and concentricity is no longer an issue due to 360º clamping of the diameter,” he said. “Plus, collet chucks are more efficient when used with bar feeders. You can work with less waste due to the fact that you can turn right up to the clamping head (collet).”
Rigidity is Essential
For surface quality and longer tool life, nothing is more important than rigidity in workholding. Recently, Walter USA LLC, Waukesha, Wis., switched from the three-jaw chuck that was formerly used in its Technology Center to a Hainbuch 100-mm collet chuck.
According to Brad Roddy, training manager at Walter USA, “When it comes to machining in a lathe, workholding is paramount. In running machine demonstrations using three-jaw chucks here at our Technology Center, we are constantly battling to ensure tool forces aren’t too high to force the chuck open and throw the part. We have the same challenge running with high rpms, as the centrifugal forces also open the chuck jaws with similar results. Switching to a collet chuck is a complete game changer with regard to rigidity and clamping forces. Being able to push our tooling to the limit and as fast of an rpm as we want is why I am an advocate for collet chucks.”
Essential to today’s manufacturing environment is not just improved technology but improved economy. That’s why one of the great advantages of high-precision collet chucks is found in the ease with which they can be retrofitted to older turning equipment. This not only increases machine capability but does so at a fraction of the cost of a new unit. In other words, today’s machinists should never settle for “this is the way we’ve always done it.”