Archive for January, 2012
How to turn bottle stoppers
Thursday, January 12th, 2012I decided to add another class to the TechShop schedule and wrote this one up last week. It’s fairly basic, but I’m hoping it will attract some folks just getting started with turning. Stoppers make an excellent beginner project as they offer more freedom than pens.
In this class, you will learn how to turn decorative wooden bottle stoppers for wine and other glass containers. Each student will leave with their own hand-turned stopper based on their own unique design choices.
Materials cost: $6
Time Required: 2 Hours
Prerequisite: Wood Lathe SBU
Tools Required
- Drill Press*
- Lathe chisels
- Bottle Stopper chuck
- Sand paper
*You can do without one, using the lathe, chuck and a morse-taper drill
SELECTING AND PREPARING THE BLANK
Bottle stopper blanks require very little wood and are a good way to make use of cutoffs from larger projects. Generally 2×2 stock is used at lengths of anywhere from 2 to 5 inches depending on the design you have in mind.
They are by definition spindle projects, meaning the grain will run the length of the lathe and not across. This is mainly to ensure the holding integrity of the screw portion of both the chuck and the finished stopper.
Exotic hardwoods tend to make the best stoppers, but really any wood can be used. A good stopper design takes the wood grain’s appearance into consideration. A particularly elaborate and vibrant grain pattern looks best on a simple design with smooth and sweeping curves. A more plain wood is better suited to some sharp turns/corners and design embellishments. The features should not compete for attention, in other words.
Another option is to glue-up contrasting woods for a more dramatic effect, or to make better use of your more expensive scraps.
The stopper portion itself is sold in several varieties from a number of suppliers detailed at the end of this manual. They range in material, style and price from between $6 and $10 each, or less if you buy them in bulk.
Most use the same size screw thread, but that is something to check before you purchase the pieces only to find they will not fill the holes you drilled. What we will be using for this class requires an 11/32 hole be drilled into the blank for both the chuck and later the stopper kit.
After selecting your blank, locate a center on the flattest plane of end grain. As this surface will be flush with the stopper hardware, you want to be sure the surface is clean, flat and exactly perpendicular to your drill.
The drill depth should just slightly exceed the screw length on the stopper hardware. Always go slightly over so the wood will seat properly when assembled.
MOUNTING THE BLANK
We use a Penn State Industries bottle stopper chuck for this class. It’s designed to screw directly onto the 1x8TPI spindle of both wood lathes at TechShop. The flat surface at the end of the screw thread exactly matches the diameter of the stopper hardware we are using, though you can easily cut a wooden washer of a different size to match other stopper diameters as show in the photo below.
I add painter’s tape to the end of the chuck to avoid accidentally rubbing the metal when sanding these small pieces.
With one hand holding the spindle steady, slowly screw the blank onto the chuck, being careful to keep the piece perpendicular as you twist.
Do not over-tighten or you will damage the wood threads needed to hold onto both the chuck and later the stopper hardware.
When properly mounted, there should be no gap between the blank and the chuck and no “play” in the wood blank. If you don’t have this tight fit, it is still possible to save the wood by removing it and filling the void with a mixture of wood glue and sawdust.
After a day or so of curing, the drilling process can be repeated with more care.
There are other types of mounting chucks for bottle stoppers, including one from WoodCraft that simply mounts inside of a morse-taper drill chuck (at right). While these are quite serviceable, they are more easily bent or damaged by an errant knock with the roughing gouge or tool rest.
ROUGH TURNING THE BLANK
Because the diameters are well below 3”, there is no need to first cut the corners off of a stopper blank.
For the same dimensional reason, it is preferable to bring the lathe speed up from the standard 500 starting position to something over 1000 rpm.
In fact, if you are confident and comfortable you can even skip the roughing gouge and begin with a larger skew chisel or a medium-sized spindle gouge.
But for the less experienced turners we will start with a speed of just over 1000 rpm and use the heavy-duty roughing gouge to at least knock the corners off of our blank. It is also safer for beginners to bring the tail stock up to the piece to further secure it between centers. It can be removed later, when most of the rough turning is complete, to access and complete the top of the stopper.
Because the piece is so small, it’s even more important to first rub the bevel on the roughing gouge so as not to accidentally knock the piece loose from the chuck mounting. Once you hear the bevel rubbing lightly against the corners of the wood, raise the back of the tool handle slowly to find the cut.
Once the large corners are removed (above), or after you are completely round, it’s time to switch to a spindle gouge. If the piece is round and true, you could start with as little as a ¼” spindle gouge. In this photo I chose a 3/8” gouge because 1) the blank was not yet completely round and 2) my design would have only larger, sweeping curves and no tight corners.
TURNING THE FINAL SHAPE
This is where your spindle technique comes into play. It’s one thing to have an idea but another thing to execute it as you envisioned.
The good news is that the only critical dimension is where the wood meets the chuck, and even that can be altered for design effect.
Be patient and think ahead about the shape you want. Like a sculptor, you must remove material gradually to reveal the shape. This is not pottery – you can’t add wood back once it’s been cut away. Watch your shape evolve and amend or correct the design as you go.
Here are some techniques to remember and practice on small spindle projects:
- If you haven’t already, bring the speed up to where you are comfortable (1-2k)
- Rub the bevel before and throughout almost every cut.
- Avoid scraping the wood. You want shavings, not dust, to ensure a quality cut.
- Use your body to move the tool and adjust cutting angles, not just the wrist.
- You are not the motor, the lathe is. Present the tool and let the wood cut itself.
- If you find you are pushing on the tool, change your angle of approach.
- Always cut downhill, from the thickest point (diameter) of wood on your curve.
- Start beads at the top of the hill, end coves in the middle of the valley.
- Stop to clear wood away so your tool can finish a tight curve cut.
- Work both ways sequentially: left/right/left/right, not left/left/left, right/right…
- Sneak up on bead with curving cuts; don’t try to hack off a corner in one pass.
- To round the end, the gouge needs to be completely on its side (photo above)
- On dramatic wood grain, the shape is easier to see while the piece is spinning.
- Try to make your final cut(s) in a single, uninterrupted motion.
- Your hands can judge a smooth surface better than your eyes.
SOME THOUGHTS ON DESIGN
As noted earlier, a general rule is to balance the elegance of the wood itself with the shape and design you select. But there’s even more to it than that.
While these stoppers are made to preserve wine, spirits or other liquids, they probably won’t spend most of their time in the bottle. That’s something to think about when you are determining a shape. For many, I like to create a flat surface or ring at the top so the stopper can sit on the table upright and not roll away.
Some people want the stopper to have a very low profile so the bottle can be stored in a fridge or on a shelf without a massive sculpture protruding. Some manufactures even sell especially low-profile stopper hardware to ensure only the wood portion sits proud of the bottle’s neck.
You can turn basic or elaborate shapes, tight contours or whimsical curves, even themed designs like a top hat or snowman. Practice on cheap scrap wood, then execute them on your choice blanks. Your friends will be amazed and grateful.
SANDING AND FINISHING
Since the wood portion of the stopper never comes in contact with the wine, we need not worry about food-safe finishing. But as this small piece of art is designed to be held, you want to achieve the smoothest possible surface and seal the wood to avoid staining from any accidental contact with spilled wine or spirits.
Sand with small strips of paper used for pens and other small items. A box of various grits will be provided, but you will need to supply your own later.
Start with small (3-inch) strips of 180-grit paper and lower the lathe speed to medium, or about 800-1000. Hold the paper in one hand and rub from behind, as in the photo above. Move your hand from left to right – constantly — and press only lightly. If the paper starts to get uncomfortably warm in your fingers you need to back off. You may also hold both ends of the paper and pull it across the wood, though this method makes it more difficult to judge heat build-up.
This first grit is your only chance to correct any slight ridges or bumps that you failed to turn away. All other grits can only remove scratches left by the previous grit. Keep the paper moving, but focus more on any such areas until they are smooth to not just your eye, but your touch.
Repeat with progressively finer grits, (220, 320, 400, 600) applying less pressure for less time to remove the scratches of the previous grit. Finish each grit with the lathe off by gently rubbing with the grain – along the length — as you slowly rotate the piece by hand.
You can now apply a sealer to the wood while it’s still on the lathe. There are many options, but I like to use EEE Ultra-Shine polishing wax.
You can then use Pen Polish, a wipe-on poly, spray varnish, mineral oil or even shellac. The finish should be applied before attaching to the stopper hardware.
That’s it, simply unscrew the blank from the chuck and screw it onto the stopper hardware. If the fit seems a little too loose, a few drops of CA glue will ensure it won’t twist off down the road.
Bowl turning 1: Wood Selection
Saturday, January 7th, 2012While there are many types of wood that can be turned, there is a major difference in approach based on the freshness of the wood to be used.
Green turning
- A fresh cut log has high moisture content; usually anything over 12% moisture is considered wet wood suitable only for roughing or purposely misshapen pieces. A moisture meter can be used to determine the percentage, but experience allows some to judge simply by the weight and type of wood.
A fresh log can be cut and the ends painted with wax or Latex paint to retard drying, which leads to cracks. Logs left completely round are also more likely to crack from shrinkage, so it is best to split them in half immediately before applying a coating to the cut ends. It is important to remove the central pith from most split logs before turning, as pith left on the finished piece will most certainly turn soft or punky and crack in time.
Normally a blank is cut from a half-log segment and first mounted cross-grain on the lathe with the bark or outer curve pointing toward the tailstock. This allows maximum depth and use of the wood as the outer curve becomes the rounded bottom.
An effect known as natural-edge bowls can be accomplished by reversing this mounting, placing the outer bark against the headstock and later hollowing the bowl to leave a bark or natural edge to the lip of the bowl, which will necessarily have low and high sections rather than a flat circle across the horizontal plane.- Fresh or green wood turns easily with little dust. Often long, curly shavings are produced as the softer wood is more easily sheared from the blank.
- But as moisture leaves the wood, what was once a perfectly round bowl will soon begin to change to an uneven elliptical shape as the wood along the grain loses moisture at a slower rate than at the ends of the grain.
- The impact can be dramatic and will often cause splits and cracks in the wood unless steps are taken to even-out the moisture loss — mainly making all of the wood roughly the same thickness and leaving enough wood on the shape to allow it to be later turned round again.
This process is known as roughing out, and generally means creating the general outer and inner bowl shape while leaving at least 5/8″ or more thickness in the wood. These roughed blanks are then left to dry for a period of months in the hopes that the wood will maintain its integrity enough to allow remounting and turning to completion. The larger the diameter, the more warping will occur so the rough blank should be left thicker.- There are various techniques to the drying process, but the most common is to periodically note any weight changes in the piece. The bowl will become lighter as it loses moisture, and when it stops losing weight it is ready for final turning. This process can take several months depending on material and climate variables. By then it will be far from round and will require reshaping between centers to round a suitable foot for chuck-mounting.
- Turning a green/wet bowl in one session is possible, but you run a great risk the piece will split and crack within days or hours — or even minutes while you are sanding it to completion. That said, some turners have created interesting warp shapes by turning wet wood and drying it quickly in a microwave.
Dry turning
Often a commercially prepared or purchased blank is used for bowl turning. These are usually covered in wax to limit moisture loss and generally are per-cut as circles ready for mounting. They are also sold as squares and need to be cut into a circle using a band-saw just prior to mounting on the lathe.- While the circle need not be perfect, you will save time, wood and energy by getting as close to round as possible. NEVER use a roughing gouge to make your bowl blank round. This is a spindle tool intended to work in-line with wood fibers and never cut across the grain. This gouge will aggressively tear out the wood fibers and leave your blank anything but round.
- Dry wood turning requires especially sharp tools and may generate more dust than shavings at different points in the turning process. No wood is perfectly dry and will always move or change its shape as you turn away its bulk. With dry wood there is little moisture to allow the wood fiber to flex with pressure, so care must be taken as the bowl thickness diminishes.
Woods to use or avoid
- Opinions vary, but generally any kind of wood can be turned with varying difficulty and success. Woods with more course grain, such as Oak and Ash, are a challenge to turn as the grain makes it very difficult to achieve a smooth surface. Pine is perhaps the least preferred turning wood as the wood fibers are too large and provide little structural integrity when mounted across the grain. There are far more exceptions and opinions on these matters as there are types of wood in the world.
- A good wood for beginning turners on the East coast is Poplar, since it has a fine grain, is relatively soft and inexpensive due to its availability. Another local favorite in the southeast is Maple, particularly the spalted variety with its color variations and distinctive markings.
Turners also like to refer to FOG wood – Found on Ground – which usually means just that the turner has little idea of the actual species. Any wood should be free of checks, voids or excessively soft and “punky” areas. While some cracks may be visible on a face, use a band saw to cut some of the cracked surface away to ensure it does not continue deep into the wood. Once mounted and spinning on the lathe, you want ensure the block has structural integrity as you remove large sections.- If you are unfamiliar with a particular wood, take care to use breathing protection and watch for skin reactions to the dust or shavings. While people can have or develop all kinds of wood allergies, be especially wary of exotic foreign woods until you have worked with them. Even a simple local piece of spalted maple can cause breathing problems as the spalting we favor so highly is actually a mold growing within the wood that will become airborne as you shave or sand it.
Bowl turning 2: Mounting the blank
Tuesday, January 3rd, 2012To complete a bowl you will need two — sometimes three — different mounting methods to turn the outside and interior shapes.
- This first mount is for shaping the outside of the bowl and the bottom foot (tenon or recess) for remounting.
- Next, we flip the bowl and mount the foot in chuck jaws to allow access for hollowing the interior.
- The last mounting is optional, but requires special jaws to reverse the bowl on its lip to get access to dress or remove the mounting foot. Professional turners do this to show the quality of their work, making it impossible to see how the bowl was attached to the machine.
- The preferred first-mounting method for most turners is to use a screw chuck, where a hole is drilled into the face that will later be the hollow side of the bowl. A special screw that comes with most chuck sets is locked between the jaws and the wood is screwed into the mount, compressing this face against the jaws of the chuck for the optimal 2-surface jaw contact. This allows full access to the outside and bottom of the bowl, where a tenon is added for later reversing the bowl and hollowing the interior.
- (screw chuck and wood with prepared hole)
Another method is to use a faceplate, which is a flange with several smaller screw holes that can be used to grip the wood. The finished assembly can then be screwed onto the spindle thread of the lathe’s headstock. This is preferable for turning large-diameter bowls or platters where there may be insufficient wood depth for the larger screw chuck.- A third method is to mount the blank between a spur center and the tailstock, locking it in place for turning the outer profile and tendon for reverse chucking. The tailstock limits some access to the bowl bottom but this is generally easy to work around.
