Today’s Workholding Demands Provide Manufacturers a Whole New Challenge
Ever since the beginning of lathes and the turning of round stock, the 3-Jaw Chuck has been the norm for every shop. Initially, there was the Manual Chuck. For years this was the staple for workholding on lathes. Eventually this led to the Power Actuated Chuck which came in various Master Jaw styles – with or without thru holes.
Similar to the path of the auto industry, various chuck models entered the shops designed for particular manufacturing needs just as Car Models were made to suit people’s needs. All were arguably improvements…Self- Centering Chucks, Compensating Chucks, Pullback Chucks, and Anvil Chucks.
Special Automatic Index Chuck is used for machining Elbows and Tees in the Valve Industry
These also came in an assortment of Master Jaw designs such as Tongue & Groove, Acme Serrated, Square or “Vee” Serrated. Others came with extended jaw strokes.
There are still many chucks manufactured fifty years ago that are still working today in making quality parts.
With the demand for higher speeds and feeds, improved surface finishes and tighter tolerances came changes in manufacturing. Manual Lathes were replaced with CNC Controlled Machines. The tooling industry developed Coated Carbides to attain the higher demanded speeds and feeds. To reach these goals, chuck manufacturers had to respond with workholding devices that could meet the situation and its demands.
Today, the situation for workholding has taken on a whole new meaning.
High Speed Counter-centrifugal Chucks, Index Chucks, Chucks with shifting Centers, Compensating Chucks with Collets or Mandrels are becoming the norm on lathes.
As the lathes take on the look and capability of a “Universal Machine”, the situation requires versatility in the way a part is gripped. To meet today’s demands, manufacturers have a whole new challenge.
Originally, production requirements were high volume. The situation allowed multiple operations over a number of machines. Each machine was somewhat specialized in the sense that achieving changeover required much downtime. Therefore, when a changeover was required, it was limited so as to not disturb the production. This, in turn, caused machines not to work efficiently at the available speeds or feeds because the tools were “OK” or the chucks could hold a variety of parts efficiently.
Multi-Spindle Chucks in a variety of 2 and 3 jaw configurations are most commonly used in lathe work
These lathes I speak of not only have the capability to turn parts at high speeds and feeds with better accuracy and repeatability, they also have the capability for drive tools, milling capabilities, automatic gaging, tool offsetting, automatic load/ unload, spindle positioning and backworking. All these options allow for many parts to be completed in a single operation, with one setup and one clamping.
Now, let’s look how the above can be accomplished and go through the thought process in determining the best possible method to hold our part.
The obvious goal is to make your product in a single setup… in the fastest time …at the least cost… and of the best quality.
It sounds simple. However, that is one loaded objective. In most situations, all the ingredients are not available. The machine may not have all the needed capabilities. The costs may not be justifiable, or the required quantities may determine the process. The variables go on and on.
Initially, the chuck size has to be established. You want to make sure the part will fit safely and securely within the envelope of the chuck. Like everything else, there may be exceptions. The part may not always be round, or may have an extended arm, which will require a counterbalance.
Next, the type of chuck has to be determined. A common 3-Jaw Chuck is appropriate for most turning applications. However, if the part is rectangular in shape, a 2-Jaw Chuck may suit the part better for gripping.. Another option may be a Collet Chuck or Mandel to maintain concentricity requirements between operations.
Review the part print and the tolerance requirements to define the process method(s) and to obtain your objective…a consistent quality part in the least time. To accomplish this goal is to establish the process suited to the dimensional and finish requirements of the part. Datums are established for a reason. Know where they are and use them accordingly in your setup.
Production will dictate the process and tooling more than anything. If you have a job of major volume, you will want a power actuated fixture that allows the ease and quickness to load/unload in the shortest possible time. On the hand, if you are going to make only one or two pieces, you would use a manual chuck with top tooling capable of holding the part at the speeds and feeds necessary to cut the part. However, this is probably not the most efficient method.
Selecting the proper workholding method is just as critical as determining the correct cutting tools, speeds & feeds, and process. Like the aforementioned items, there are references, recommendations and many vendors with expertise to assist in the selection process. It would be to your benefit to use these knowledgeable and experienced resources to guide you.