Lathes

Basic descriptions of lathes and related equipment. November 11, 2008

Reprinted with permission from MLS Machinery, Inc.

In most cases lathes produce a single piece at a time, example lampshade, billiard cues, gun stocks for rifles, etc. Lathes can be for the small home hobby type operations or for mass production.

How lathes work: a "square" which is a piece of wood that has been glued together to a desired length and width being slightly longer and larger in diameter than the final product, is placed into the machine between holders so that it can rotate. As an example a lamp stand which will eventually be two-inch diameter by ten inches long might start off as an oblong "square" piece, 2-1/2" by 11" long.

Two main systems of lathes are used to produce the finished turned part, they are the back-knife lathe and the copying lathe. The back-knife lathe has a big cutter or long knife running along the full length of the piece to be made (turned). The hydraulically controlled knife in most cases (hydraulic to exert a large amount of pressure) comes down in progressively slow increments and forces itself into the wood while the part is rotating. The knife or knives, which are the exact shape of the piece that is actually being made, will stop once it has reached a pre-determined stopping point. The knife or knives will then retract waiting for a new part to be installed into the machine.

Another method is by using a copying lathe where a pre-made sample or template is installed in the machine. A following or copying wheel follows the original or the template, which has a knife attached to it and will cut out the part as it follows the original pattern. Some machines can make multiple parts of the same at one time. These machines are normally either hopper fed, so that the squares are placed in a hopper and the machine will automatically feed itself as well as kick out the completed parts, or, multiple parts will be placed into separate holders thus allowing 6-24 parts exactly the same to be made simultaneously. These machines are normally for large production.
Once any turned part is completed, the parts have to be sanded. For large production there are some sanders that are hopper fed and will sand multiple complicated turned parts at the same time, normally working very similarly to the lathe with a template and copier. Some less expensive multiple sanding machines use multiple pieces of sandpaper along the length of the part that oscillate while the parts turn around the sandpaper.

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