In modern tooling or machining, the work holding system is needed to hold a part or a work piece still and firmly to be worked. The major work holding systems that are applied in a machining or working procedure is clamping vises, fixtures and chucks. They are all useful in holding parts in the lathe and they have their own roles to play in the working operations.
A scrolling chuck is one of the work holding chucks with self-centering or self-closing jaws to clamp a part. Unlike a vacuum chuck or a vacuum table, the mechanism of the scrolling chuck to secure work pieces is more identical to that of a vice. The configuration of the jaws on a scrolling chuck is like a claw and it literally grabs the piece in the center of the claw. Typically there are three jaws on a scrolling chuck, but there are multi-jawed models of scrolling chucks on the market as well.
The body of a scroll chuck is a round, plate-like base. The center of the chuck body is hollow so that it looks like a ring. There are keyways crossed from the outskirt of the ring to the hollow center of the base. The keyways are the grooves for the jaws to be centered. The jaws of a scroll chuck contain two pieces: the bottom jaws and the top jaws. There is a part called rack on the bottom jaws; the scroll base engaged the rack to close or open the jaws at the same time. The bottom jaws and the top jaws are interlocked, so when the bottom jaws close, the top jaws close too. The top jaws are the parts that actually clamp a work piece.
The jaws of a scrolling chuck are sometimes called dogs. The numbers of jaws, or dogs, on a scrolling chuck determine what kind of pieces it can clamp the best. With more jaws, a chuck is considered more powerful to secure the work piece. For example, a four-jaw scrolling chuck provides easy clamp to a square piece; however, it is more likely to mar the piece. Just like the vices, the jaws of a scrolling chuck can be made with different materials and designs to hold different pieces.
The properties of a scrolling chuck and a vice are alike in many ways. The mechanism of a scrolling chuck is a bit more complicated than a vice but the clamping approach is similar. They both clamp a work piece by closing the jaws together. However, what makes them substantially different is the clamping mechanism as well. A scroll chuck is the most idealistic option for bowl turning. In a bowl turning, the clamping of the work piece is not to close the jaws but to open the jaws instead. The opened jaws can push firmly against the recess of the bowl to its bottom so that the bowl is secured still.
In addition, the open and close of the jaws on a conventional scroll chuck is performed in unison. To be exact, the open or close level of each jaw is the same and the force to each jaw is the same, too. The advancement of a modern scroll chuck makes it possible for the jaws to have different degree of opening and closing in order for the chuck to fit as many measurements for work as possible. For the works that involves bowl-turning, the four-jaw scroll chucks are the most preferable. The four-jaw scroll chuck is suitable for most measurements for work holding. Four-jaw design also provides the best clamping to both round and square work pieces.
A scroll chuck is useful not only in bowl turning, but also applicable in lathe machining or lathe operation. It has been incorporated as a part of CNC machining in the manufacturing industry nowadays and has further developed into different subtypes to meet more requirement in the tooling and machining to date.
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