by Valerie and Paul Carter |
November 19, 2014
Many turners have walked into their favorite woodworking store, checked the price tag on a beautiful bowl blank, and nearly fainted. Why is wood so expensive and how can you find, and turn, free wood?
For spindle work most turners look for seasoned wood. You can find inexpensive chunks of seasoned wood for your spindle work from several sources:
- Narrow pieces of wood that wood dealers have a hard time selling.
- Discarded wood from cabinet or furniture makers. Oftentimes called 'drop.'
- Firewood
- Skids and pallets are a great source of thick timber. Pallets coming from the orient are oftentimes made of beautiful exotic woods.
Faceplate work is generally quite pricey because thick seasoned wood for bowls and the like is considerably harder to dry. There are some places that you can look for great wood for faceplate work, however.
- Road crews that cut down trees are often willing to give away wood.
- Private tree trimming companies are also a great source for free or inexpensive wood.
Most wood you'll find from these sources, however, will not be seasoned. Rather, it will be green wood. A felled tree is about 60% water. As the tree dries water slowly drains from around the cells of the tree until, at last, the cells themselves begin losing water. As it loses water the wood will begin to shrink. This is when the green wood cracks.
Perhaps you're thinking, what's the point of finding free green wood if it will just crack? Thankfully, there are several ways you can avoid cracking.
First of all, the portion of the log that you cut your blank from is critical. It is necessary that, as Ernie Conover, a well-known turner states, "no chunk [of green wood] contains a complete annular growth ring." As shown in this image:
Once you've cut your green wood, it is important to keep the elastic limit in mind. The elastic limit is basically how much a piece of wood can bend before breaks or cracks. As you can imagine, a thinner piece of wood will be able to bend much further before it breaks. That is why large and thick green bowls are more likely to crack while they are shrinking and losing water. Ernie Conover talks about wall thickness, advising that, "a good rule of thumb for wall thickness is to make it no more than 10% of the largest diameter. For a 8" diameter bowl, make the wall 7/8" or less."
After you have roughed out your bowl, allow it to dry for at least 3 months before giving it it's final shape. A good idea is to wrap your bowl in paper while it is drying. This will slow the loss of moisture and help prevent cracking.
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by Paul Carter |
September 09, 2014
Steel is an amazing material. It comes in an array of types, from stainless to high speed. However, it is often the heat-treatment process that makes steel usable for hundreds of applications.
Steel is shipped from suppliers to machine shops around the world in an annealed state. Because this is the steel's softest and most relaxed state, machining the steel in this form is much easier. Heat-treatment always takes place on annealed steel. Once a steel has been heat-treated, it can be returned to it's annealed state. Steel cannot be re-heat-treated without first being annealed.
Once the steel has been machined, it moves onto heat-treating. The steel is hung on wires and then heated to hundreds of degrees Fahrenheit. Different types or grades of steels can be heat-treated to different harnesses. The steel used for our tools, M42 high speed steel, has a 10% cobalt content. This cobalt allows us to heat-treat our tools harder than most high speed steels, to a hardness of 68 HRC.
After the hardening process, the steel is very brittle and pressured. This is why tempering is the next step in heat-treating. Tempering reduces the internal stress of the steel and increase the steel's robustness.
Once the steel has been tempered it is ready for use in a huge warehouse, machine shop or at your lathe.
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