Compression provides the necessary force for holding the can against the chuck and to feed the flange of the body into the first roller. Every closing machine has a base plate and a chuck. The snugly fitting chuck holds the lid in place and provides support for the seaming rolls pressure. The base plate is spring loaded and pushes the can up against the chuck.
All round cans are classified with diameter x height dimensions, for example 307 x 409 and 307 x 200. Every time the diameter (the first number) changes, a proper chuck must be installed. In the above example the cans have different diameters so 307 and 301 chucks must be used. When a crank handle is turned, a set of gears transfers the movement to the chuck which starts turning. The grooves on the chuck force the lid to turn as well. The chuck fits snugly into the lid. Its disc has many groves on its side and those grooves lock the lid.
Turntable, also known as base plate, is a free spinning disc that supports the can. The chuck propels the lid that sits on top of the body of the can. Without pressure the lid will continue to spin on top of the can and the can will remain stationery. The lid and the can must be compressed together and this is accomplished with a locking lever. There are two designs for applying pressure:
- Ives sealer lever pushes the chuck downward towards the lid.
- All American sealer lever moves the turntable upward against the can.
The result is the same in both cases; there is pressure on a can from both ends and the whole system: the chuck, the lid, the can and the turntable starts spinning as one.
The tallest can may get the correct amount of pressure from the spring alone, however, a shorter can of the same diameter will need a spacer. For example a small salmon can 307 x 22 and No. 2 can 307 x 409. Both cans are sealed with 307 chuck, but they will need a different spacer to raise or lower the turntable.
A few spacers may be placed together, however, there is a limit how much the shaft may be raised before it starts to wobble. The table extension spacer is needed for sealing short cans. When ordering cans with different heights, make sure that you order the correct spacers.