Thursday, February 22, 2007
Thank you Cyndi! You asked some searching questions that made me really think about things I take for granted in my day to day work.
Thursday, February 15, 2007
Anyone setting out to dry their own lumber will benefit from a basic understanding of the physics involved. The rate of drying is determined by the temperature, relative humidity and air flow. The final EMC is determined by the relative humidity:
Raising the temperature not only makes the moisture more mobile within the wood, but also reduces the relative humidity. If you want to know more about drying wood I highly recommend reading Wood and How to Dry It (Fine Woodworking)
I usually err on the side of caution when seasoning wood to avoid defects such as splits or honeycombing so I try to be patient and let the wood dry slowly. Every piece of green lumber has its end-grain sealed with either paraffin wax or proprietary end-seal.
It is then stickered somewhere cool to air dry to below 20%, preferably 16%. This may take some months, but unless I am in a particular hurry, this is better than risking it splitting. The back room in my workshop is cool, and makes a good starting point. After a month or two I may move it into more normal room conditions until I think it is safe to put it into a 'kiln'.
A moisture meter is an invaluable tool to help you assess how drying is proceeding.
One simple way of drying wood that I have used in the past is to place a table (plywood and folding legs, not a good one) over a hot-air floor register. A cloth is draped over the table top, large enough to reach the floor all the way around. It is weighted down at the back and sides but left free at the front to encourage hot air to pass all the way through the chamber.
Wood is stickered inside, leaving a space above the register to promote even airflow. The advantages of this system are that it is cheap and easy to set up, and costs virtually nothing to run as the heat eventually warms the house. The main disadvantage is that the operating temperature and humidity can only be controlled by adjusting the register or lifting the table cloth. As a rough guide I find that it takes one month for every inch of thickness. The whole contents are removed and checked once a month. Anything dry enough to use is removed. The remainder is returned to the back of the chamber nearest the register and any free space filled with new wood. The temperature can get up to 40°C and the humidity down to 40%, but generally it runs at about 30°C and 55%. This will depend a lot on the humidity in the house and how much the furnace is running. I find that most woods get down to about 8% EMC. It doesn't work anywhere near as fast as a commercial kiln, but is far better than air drying alone.
I have dried 3.5" oak from green to 10% in less than 9 months using the two techniques above..
The 'kiln' described above obviously isn't going to work during the summer months, so I have a simple solar kiln in the back yard. It is essentially a greenhouse, a wooden frame covered in UV stabilized polythene. Black polythene is stapled to the inside of the frame in order to keep direct sunlight off the wood, and to absorb heat.
Sunday, February 11, 2007
My solution is to tie a piece of high visibilty marker tape to it.
In six years of use I haven't lost it yet.
Now, where did I leave the remote?
Friday, February 09, 2007
We might also get more adventurous by using other techniques such as pyrography, painting or carving to add a repeating motif to our work.
I was prompted to bring this subject up by a post by Karl Zipser on Art & Perception titled Is grownups’ art art?. Karl is comparing the design on some eigth century pottery to something made recently by a child, but in doing so shows how the child's work can gain a sense of rhythm and complexity by repetition of the whole design and elements within it. It really is worth taking a look to see how this has been done and the impact it has.
If you want to study this some more, there are plenty of examples of repetition in A Study of Different Modes of Repetition in Art and Design, and a nice little tutorial on the subject at Principles of Design - Repetition.
Do you use repetition in your designs?
Thursday, February 08, 2007
This seems to be a blog with a mission. Philip is critical of the British woodturning scene:
"...the focussing of attention in British woodturning on matters relating to technique and finish, was inhibiting the growth and development of the craft."
So this is what Woodturning Plus is going to be all about:
"This Blog is intended for those in the UK who ...... have found their current sources of information or encouragement either unsatisfactory or unchallenging. I will be adding entries that may help creative thinking and doing, using net and book references. ....... It will be for you ..... to find your own solutions using the same trial and error processes that most makers in other disciplines use to achieve their unique designs for any given project or method of working.I don't think this is an issue restricted to the UK, so I am sure that his blog will be of interest to wood turners from around the world. I don't think that the 'problems' Philip perceives are geographic. There are certainly some fine and creative woodturners in the UK. Wherever we live I think we need to be aware of the woodturning culture that we expose ourselves to, whether it is clubs, periodicals, galleries or shows. This culture is not just about design, but also things such as quality of workmanship, and skills and opportunities for marketing and promotion. Education is another factor. Someone with a degree in fine arts is going to have a huge advantage in terms of design matters over someone who comes to woodturning as a hobby and is just wanting to be able to make things. And there is nothing wrong with this, but I do agree that there is a big distinction between a craftsman and a designer-craftsman.
So if you are reading this and you are a woodturning craft fundamentalist having no wish to see tools used incorrectly, grain abused and alternative materials used with wood, then this is not the site for you."
Long time readers of The ToolRest will know that I am thinking along similar lines to Philip, and have blogged about some of these issues in "Who influences your work?" and "Inspiration for woodturners". In those posts I have attributed some of the blame for these issues on the woodturning press. For example, when Woodturning Design first came out I had high expectations for some refreshingly different content, but unfortunately I now realise that they really meant to call it Woodturning Designs, or maybe Woodturning Projects. Too bad. Anway, I hope that Philip and I can keep some sort of dialogue going between our blogs and provide some content that is lacking in the mainstream press, or maybe even encourage them to change their focus. I am not going to be as radically selective in my content as Philip though, and you can be sure to continue to find tips and techniques here too.
Before I sign off, I should point out that Philip also has a website, woodturningdesign.info, which has some very nicely presented papers, such as 'An Introduction to a Design Method for Woodturners'.
Tuesday, February 06, 2007
The two things that I tend to forget are drill bits and the tailstock. I do a lot of drilling on the lathe, typically several thousand operations a year. I use mainly brad-point bits when making bottle stoppers and weedpots. If the flutes of the drill bit get clogged with wood chips, the drill gets hot, and a lot of effort is needed to feed the drill into the wood. Sharpening a brad-point bit is quite straightforward on the grinding wheel, and uses less skill than sharpening a gouge. After touching it briefly to the grinder, check that both tips project equally far forward by holding the bit up to a try-square. Keep the angles of both bevels the same, and if the brad itself needs attention, be sure to keep its tip central.
I just sharpened my 3/8" bit today, and it now cuts cleaner chips and requires less force on the tailstock hand wheel to feed it into the wood. It feels like it is cutting better, and the chips seem to eject from the hole much easier. While I was in the maintenance mode, I also cleaned the flutes of the drill bit and even carefully gave them a polish with an old buffing wheel loaded with Tripoli. Anything that helps eject those chips is worth doing. I can now run the lathe a bit faster too.
One problem with using the tailstock for drilling is that it puts a lot of stress on the tailstock spindle where it bears on the striker plate. Periodically I strip down the tailstock and clean out all the mess and file away any scarf that has been thrown up. Recently I left it too long between services, and had great difficulty disassembling the tailstock. Its not a pleasant job, but much easier to do before the tailstock jams up. A good indicator that things are not quite right is if the tailstock spindle becomes hard to wind in or out under no-load conditions. I use powdered graphite as a lubricant, the same as I do for chuck maintenance.