Thursday, June 21, 2007
I have steered many clients away from the idea of keeping their chairs outside. The type of joinery and the thickness of the wood in a Windsor chair doesn't lend itself to weathering. But I have so many kicking around that I keep a few on the porch year round. They get hours of direct sunlight, snow, rain and constant use (wet swimsuits and all). It has been a great testing ground for the weak points of the construction. The chair you see in the images has been outside for about 5 years. As you can see, the knuckle is cracked ( I no longer glue on hands, preferring to make them integral to the arm), the legs are split and the bow has suffered a catastrophic break.
The amazing thing about it is that we use this chair, cracks and all, and it doesn't even creak. I take it as a tribute to the brilliant technology in the Windsor chair. Each piece is a part of a web and the minor failures shown don't affect the whole. Of course, at some point in the future, I expect the chair to break, I'll be curious to see where. But it does give me confidence in the longevity of the pieces that are kept indoors.
This will be my last post for a while, I am heading down to teach at Penland until early July. I could have my house sitters post about my dogs misbehavior (Lily has learned to rip through screens, 4 and counting), but I'm sure you have better things to do. I am looking forward to posting images of the projects and ideas the come from the class. Going to Penland always seems like a vacation, until I get there and work harder than I do all year!
Monday, June 18, 2007
I've been working more with my forge in preparation for my teaching engagement at Penland. It has been as fascinating as it has been humbling. Pictured are my first attempts at making froes. The rough looking one on top is my initial try. As crude as it looks, it gave me a first crack at many new skills, such as, localized heating, forge welding, tapering an edge, creating a round eye and not burning myself.
After a conversation with my blacksmith partner, I was ready to give it another go. Much better. This improvement is a great example of the learning process as I've come to understand and enjoy it. When I attempt so many new skills at once, I focus on the huge leap that occurs between knowing nothing and knowing something. Often the end result is only pleasing as a representation of this learning process (hence the ugly froe). I am looking forward to going down to Penland and watching the experienced blacksmiths move the metal around, now that I've tried it, I can appreciate their skill all the more.
Saturday, June 16, 2007
There is nothing wrong with sandpaper. It is a cutting tool and used with skill can be effective. There are also times where difficult grain, raised fibers, or wood under compression (such as the inside of a steam bent curve) may need some sanding to achieve the desired surface. With that said, I try to eliminate sanding as much as possible.
To me, sanding is a slow and dusty way to arrive at a surfaces that have a "sameness" that I don't find appealling. Nothing can match the surface left by a razor sharp tool used in the correct manner. I like to think of the tools that I use and the process as being clearly represented on the surface of the piece. Every time that I reach for the sandpaper (and at times I must), I feel like I am mumbling to cover something up. But I try not to avoid sanding on some "purist" level, just to recognize that it generally points to areas in my process or ability that need deeper exploration. I simply find the challenge more fun and the end results more interesting.
I don't use sandpaper to create shapes, I use it to correct surface issues. At this point, my sanding is generally limited to areas where I have used a scraper. After scraping (a sharp scraper is vital), I wet the area and let it dry thoroughly. Then a light cutting with 220 grit knocks off the raised fibers. Learning to do without sandpaper has often slowed my works down substantially, but I have made it up many times over in the speed that I now work and the crisp surface that I can achieve.
Sanding is often necessary and sometimes very good, but I think that it should be employed sparingly and always questioned as an opportunity for better work and understanding.
Thursday, June 14, 2007
I've had a number of responses for the open July 30 class date. I've had at least one individual confirm that he'd like the date, so while I haven't figured out who is going to be in the slot (a couple of first come maybes), I know that it has been taken. I haven't posted anything about my schedule on the blog up until now, which I now realize may be a disservice. My goal has been to keep the blog as commerce free as possible, but the imposition of waiting more than a year for a class opening has changed my mind. I will post future unexpected openings as they come up and fill them on a first come basis.
Wednesday, June 13, 2007
I recently had a student reschedule his class for a later date, leaving my teaching schedule open for the week of July 30. Besides a couple of openings in the early part of 2008, my classes are full until August 08. If anyone is interested in the July week, please see my web site for details and contact me to reserve the spot. This is also open to students who are already signed up for a later date and wish to skip forward in the line.
Tuesday, June 12, 2007
The photo above shows a continuous arm bow with a bead detail. I use a simple scraper blade that I grind to the desired shape and hold in an L shaped block of wood that rides against the side of the bow. The block and blade are pictured below.
The unshaped blades can be purchased separately from any of the companies that sell the more expensive beading tools (the bronze tool shown is a Lie-Nielson beader). These tools are best suited to cabinet type work. I find them a bit bulky for the curves of a chair. I made the rough looking wooden holder about 5 years ago, thinking that if it worked well, I'd make a pretty one. It works so well that I've never bothered.
Scraping blades need to be everybit as sharp as any plane blade or chisel to function properly. The only difference is that I sharpen my beading scrapers so that the edge is 90 degrees to the polished sides. After shaping and polishing all of the surfaces, I turn a small burr to do the cutting.
The scraper in use will take shavings just like a plane, however, it compresses the surface fibers a bit, so I wet the finished piece, let it dry and then knock down the raised grain with 220 grit sandpaper. Sharp scrapers and a light touch can reduce the need for sanding a great deal. After the initial groove is established, using the wooden holder, I remove the blade and use is freehand. I find that this gives me much greater control over the depth of cut and pressure exerted.
Thursday, June 7, 2007
There are a number of factors that can create vibration and the telltale chatter on a workpiece, but most of the time, I turn to my tools and technique for the answers. I always use a shearing cut when turning, as opposed to a scraping. Scraping in spindle turning leaves a coarser surface, takes longer and encourages vibration. When scraping, the only part of the tool that makes contact is the cutting edge, unlike shear cutting where the bevel of the tool is in constant contact.
When shear cutting, the bevel rubs against the surface behind the cutting edge. This offers several advantages. The pressure applied can actually help steady the workpiece and reduce vibration. The freshly cut surface is smooth and as the bevel rides on it, the cutting edge can pare away any surface chatter, much like a regular chisel pares. This paring action also helps to create fluid shapes because it relates the already cut surface to the surface being cut. Bevel contact also reduces the chance of any nasty catches. Catches happen when the cutting edge is unsupported and is overcome by the force of the spinning piece.
In order to keep the bevel in constant contact, I've found that the shape of the metal behind the cutting edge is crucial. The hollow grind and a small flat help keep a low clearance angle, and the bevel in easy contact. If the metal behind the edge gets rounded, from repeated buffing etc... the bevel must be lifted off of the workpiece to get the edge to cut, and CATCH!!!
So anytime that I am getting chatter that I cannot seem to get rid of, I sharpen up my skew and take a light cut with solid contact. (The other thing to remember with the skew is to keep moving forward, any attempts to back up can lead to a catch.) I rub the bevel on the smoothly cut surface while "paring" away all the nasty chatter. I will often use my hand behind the workpiece to steady it as I cut with the skew, always keeping my thumb on the tool. It does take some practice and a light touch, if your hand gets too hot, you're holding too tight. After a while, you'll sense the trouble arising, adjust accordingly, and the chatter won't get there in the first place. The difficulties in learning to turn should not be underestimated. Early on I set the goal of not sanding my turnings, this led to many a botched leg as I worked to master the more difficult techniques involved. Luckily I heat my house with wood and hard maple burns like coal! The reward of this effort is the ease and speed that I now enjoy, though I never forget that I am always a tiny bevel away from disaster.
Tuesday, June 5, 2007
I generally turn green wood, although lately I've been turning some parts air dried. There is definitely a difference in the way that they turn. I do all of my green rough shaping and parting tool sizing at a higher speed and then slow down when it comes time to do my detail gouge work or skewing. Air dried wood also seems to turn nicely at higher speeds, but once vibration starts, it can be even more difficult to eliminate. Once again, slowing down can help.
One factor that may affect chatter is the pressure exerted by cranking in the tailstock. Green wood is flexible and too much pressure may not make a difference until you turn the thinner detail, at which point the wood can spring and vibration follows. I apply just enough pressure to capture the piece firmly, remembering that the headstock spurs may sink in as I work and require further tightening.
Adjusting the order in which you turn may quell some problems. I try to leave as much mass on the head stock side of the turning and finish it last so that the torque is transferred through the largest possible area. A smaller section may encourage vibration. Once you have cut a thin detail in the middle of a piece, you can probably expect chatter in the surrounding areas. When I was learning to turn baluster legs, I got in the habit of roughing out the leg and then cutting the lower cove area first. I figured that it was the toughest area and if I was going to screw up, I'd rather it be right away. Now, although I don't have so much trouble with that area, I still cut it first out of habit, bad habit. But I've learned that if the rest of the leg is roughed in and only clean up cuts remain, the vibration is manageable. Also, the relative size of details can make a difference. A tiny cove next to a huge bead may cause issues, as well as looking weird!
One of the pleasures of green wood is the size of cut that I can take cleanly without chatter, but at some point, I can always expect it to creep in. While I'd love to blame the machine or the wood, I have less control over them than I do over my tools and skills. Soon I'll address the tooling and skills that may help eliminate (or more likely manage) this problem.
Sunday, June 3, 2007
I have been thinking about a recent question that I got about lathe chatter. It seemed so simple at first, Do I use a steady rest to reduce vibration? I don't, I use my hand to steady the spinning workpiece. But that is just the tip of the iceberg of the steps and trials that I have had on my path to reducing vibration. One of my goals with this blog is to make woodworking more approachable, you don't need any mystical skills. There are just lots of mistakes and lessons, generally easy ones, that need to be had before things seem "simple". Often, once you know something, it is difficult to remember what it was like before you knew it or the path you took to knowing it.
Vibration is one of the largest obstacles to turning wood. And vibration begets vibration. Once a piece starts vibrating, the turning becomes rough and patterned, control and surface quality are difficult to regain. There are many factors that need to be addressed. The machine, the wood, the tool in hand and of course, the operator skill.
Today I'll talk about the machine. Lathes vibrate. I have an old (late fifties) benchtop Rockwell lathe with a belt that must be manually moved to change speeds. This is a perfect testing ground for vibration! The first thing to address though is the floor. I used to work out of my basement, not good. But I had my lathe on a concrete floor and bolted to a concrete wall, good. This, along with some sandbags on the lower shelf helped to steady my old lathe pretty well. Now, in the new shop, with its lovely wood floor (better on the legs and tools) my lathe absolutely rumbles. Not having the time to deal with the floor (a concrete pad seems in order), I have turned my attention to the other variables.
The motor should be checked for undue vibration. Undo the belts and let it spin on its own. A glass of water on the lathe bed is a good indicator. I have tried just about everything to reduce the transfer of motor hum. Rubber washers, motor on a hinge, tighter belts, looser belts, new bearings, you name it. One thing that I know helps, is the link type belts, with the proper length. I've used them ever since they stopped a bandsaw from walking across the shop. Checking the bearings and alignments of pulleys etc... can go a long way toward the goal of silencing vibration. There is good literature available about tuning up your lathe, after all, it's a great opportunity to blame the tool!
Honestly, I've sort of given up on further machine tinkering. Being an instructor and travelling to different schools to teach puts me in an awkward position. If I can only get results from a perfect machine, I risk being less than impressive on the rest of them! So I have turned my attention to the other factors, which I will cover soon.