Beyond the Standard Wedge or Scroll Type Chucks with 2, 3, 4 or 6 jaws many specialty chucks and styles have been common in the manufacturing arena for many years. In addition, chucks were often designed with multiple jaws to provide better wrap around gripping…especially on thin-walled parts.

As demands increased, manufacturers looked for ways to increase production via reducing changeover time from one production run to another. Engineers looked at purchasing new or additional equipment, but in most cases were shot down because of costs. Therefore, they had to search out different means of accomplishing better production, without loosing the integrity of the process and having teardown time consuming setups.

One solution was to use a 2/3 Jaw Chuck which provides the ability to clamp round parts with the equally spaced 3-jaws plus allows gripping square or rectangular shaped parts with the 2-jaws opposing each other.

For example, there may be perfectly round parts that can be gripped in a standard 3-Jaw Chuck and then the next job involves rectangular pieces where there are only two surfaces to grip. One consideration would be switching out the chucks. This would be very time consuming in unmounting one chuck and installing another. Also, there are the concerns about the drawbar setting being correct; the chuck being properly seated and how true the process will run each change over time.

One simple method is to stay with the 3-Jaw Chuck and mount a work stop opposite one of the jaws. Then, use the one jaw to clamp the part against the work stop. Unfortunately, this simple method puts a lot of pressure to the one jaw and requires the stationary jaw to be a qualified surface.

The ideal situation is a 2-jaw centralizing mode which is possible with a 2/3 Jaw Chuck. In this mode, square or rectangular shaped parts can be firmly clamped and centralized while balancing the removed stock evenly. Because of the centralizing mode, one of the surfaces does not have to be qualified beforehand as would be the case in using an Anvil Style Chuck or method.

There are some cautions associated with a 2/3 Jaw Chuck. When changing from a 3-jaw mode to a 2-jaw mode, the drawbar pressure must be reduced to eliminate possible damage to the operating wedge because of distributing the pressure with only two jaws versus three jaws. Also, with a 2/3 Jaw Chuck the weight is not evenly distributed and can not run at the same top rpm’s as a standard 3-jaw chuck.

However, the 2/3 Jaw Chuck style definitely has its place in manufacturing by greatly reducing changeover time…allowing operation for round, square or rectangular parts without chuck changeover…and providing more flexibility and opportunities for the machine. Thus, increasing production output by allowing a variety of different parts to be processed on a common machine tool.

Another option to enhance a 2/3 Jaw Chuck versatility is to have adjustable master jaws which allows better gripping control over odd shaped work pieces.

Founded in 1952, Royal Machine & Tool Corporation is ISO9001:2008 & AS9100 Rev.”C” Certified and serves the world’s leading industries from its Berlin, CT corporate offices and manufacturing facilities representing over 30,000 square feet including state-of-the-art CNC machine tools. All services and products are performed and/or produced in the USA and include the designing and building of custom and standard work holding devices from simple manual fixtures to sophisticated hydraulic fixtures with multiple faces. Custom and standard chucks of all types for rotating and non-rotating applications are also designed and built by Royal Machine &Tool…as well as a complete range of Contract Machining options/services from single prototype machining to high volume production requirements.