69 - Bench Top Storage System, страница 32

It may not be glamourous,

but cast iron is still your best

bet when buying wood

working equipment

cast iron is that it's still cheaper than many of the alternatives. The manufacturing start-up costs for cast iron are a lot less than for other materials. Since most woodworking tools are built in small numbers (thousands rather than millions), cast iron is often the most cost-effective choice.

There are places where you may notice manufacturers cutting back on cast iron. These areas are not as important from a functional standpoint. Knobs, hand wheels, and tool bases that used to be made out of cast iron are now usually plastic or stamped steel. But cast iron continues to be used on the parts where it really counts - machined tops and beds, trunnions, and gears.

Cast Iron Process - In the past, tool manufacturers typically cast machine parts in their own foundries. But with modern specialization, this is now the exception rather than the rule. Most manufacturers find it cheaper and more efficient to have their castings made by an outside source. But the process is still the same. First, a patternmaker

Seasoning, i

A stack of jointer fences is left outside for several months. This allows the castings to stablilize before being machined.

When it comes to woodworking equipment, many woodworkers will tell you that the more cast iron in a tool, the better. But have you ever stopped to wonder just why this is? What is it about cast iron that makes it so great for power tools?

Why Cast Iron? - When you think of all the modern metals and plastics that are available today, cast iron seems like an outdated relic from the industrial age. After all, manufacturers started using cast iron for woodworking equipment over a hundred years ago. But the truth is that no other material is better suited for this purpose.

Cast iron has several things going for it. First, ifs heavy, so it absorbs and dampens any vibrations from the machine. Second, cast iron is stable. It's much less likely to expand, contract, or warp than other materials. This means that a tabletop milled out of cast iron will likely stay flat for years to come.

Although it may be hard to believe, one other reason for using

▲ Pouring. White-hot, molten cast iron is being ladled into molds. After the cast iron has cooled, the parts are removed from the molds and then allowed to "season."

creates a pattern of the desired part.' Next, a mold is made to match the pattern. Then, white-hot, molten iron is poured into the mold. Once the casting has had a chance to cool off, it is removed from the mold and allowed to "season" (more on this later). Eventually, the casting is machined and finished.

Types of Cast Iron - There are several different types of cast iron. Most of the cast iron you'll find in woodworking equipment is gray cast iron. This type of cast iron is tough, stable, and machines well. The main drawback of gray cast iron is its brit-tleness. It can break or crack if subjected to a sudden shock or impact.

For tools or parts that are going to be getting a lot of abuse, manufacturers may use ductile cast iron instead. This is a more elastic form of cast iron that is less prone to breakage. You'll also see ductile cast iron used in hand tools, such as planes and clamps.

Even among gray cast iron, there can be differences in quality. To start with, some manufacturers are

32

ShopNotes

No. 69