Introduction to Wood Turning Participant Handout

Transcription

1 Introduction to Wood Turning Participant Handout Class schedule Week one Week two Week three Week four Week five Week six Week seven Week eight Week nine Week ten Week eleven Week twelve Week Thirteen Course introduction Roughing out between centers Beginning practice with the shallow fluted gouge Continue practicing with the shallow fluted gouge Pen turning/mandrel turning Bud Vase Project Planning, mounting, layout, roughing Bud Vase Project Turning, drilling parting off Turning bottle stoppers Candle stick Mounting, layout, initiating Candle stick project, continuing Candle stick project completion Miniature stool, turning the seat Miniature stool, legs Layout legs, turning Miniature stool Completion Completion of all projects Instructor: Jim Rodgers (925) Page 1

2 Woodturning Safety Rules 1. Know Your Equipment and Yourself. Never operate a lathe or use a cutting tool, chuck or other accessory without first understanding its operation and limitations. Read and know the instruction manual of any lathe that you use. Never perform a procedure or technique that you are unclear about or uncomfortable with. If you are in doubt, stop and ask for instruction. Know your personal limitations. 2. Focus on Your Work. You may not operate a lathe if you have drunk alcohol or taken medication that carries an equipment operations warning. Don t operate a lathe if you are tired or emotionally upset. 3. Police Your Environment. Keep your work area clean. Store tools safely. Don t allow cords to run across circulation ways. Don t start your lathe if people are in harm s way. Ensure that there is adequate light and ventilation. If you are observing someone else, don t place yourself in harm s way. 4. Keep Yourself Catch Free.. Long hair must be tied back. No clothing, gloves, jewelry or watches may be worn below the elbow. Necklaces and loose clothing that could be caught by spinning parts must not be worn. 5. Wear Safety Equipment. To operate a lathe or stand near an operating lathe, you must wear full face protection. Dust masks are highly recommended. 6. Secure the Wood. Ensure that the wood is securely held. Turn between centers whenever possible and always with imbalanced pieces. Use a slow speed when first roughing out a piece. Never use wood that is cracked or has other serious defects or significant protrusions. 7. Inspect Your Lathe. Inspect the lathe for damaged or missing parts before operating it. Before you start, check to ensure that the speed is appropriate, the drive belt is tight, all locking devices are secure and all chuck keys and adjusting wenches are removed. Always spin the wood at least one full turn before turning the lathe on - every time. Never leave a spinning lathe unattended. 8. Practice Safe Techniques. Keep your tools sharp. Don t force a tool or use it for an unintended purpose. Reposition the tool rest frequently to keep it close to the work. Keep your balance and don t overreach. Always turn the lathe off and allow it to come to a complete stop before adjusting the tool rest. Always keep your hands behind the plane of the tool rest. Always keep the tool firmly against the tool rest. Always hold the tool firmly with both hands. When using a shear cut, rub the bevel. When using a scraping cut, always keep the angle between the wood and cutting edge at less than 90 degrees. When finishing, always remove the tool rest. Use only paper towels, never woven fabric. On exterior surfaces, apply the towel to the underside of the piece with the wood spinning counterclockwise. On interior surfaces, apply the towel in the lower left-hand quadrant also with the wood spinning counterclockwise. Adopted by Bay Area Woodturners Association, 10 March, 2001 Page 2

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4 Observations On The Use Of Woodturning Tools I have been teaching wood turning for about six years and have taught hundreds of beginning students both adult and teen aged male and female short and tall and you get the point. Here are the few things that always seem to be beginner s difficulties: 1. Tight body a. This means a lack of freedom of movement restricting the fluid motions with the tools causing poor shaping of the project and irregular surfaces due to poor tool control. b. Rigid, tight muscles locking the tool tightly to the hand and fighting the wood/lathe combination c. All body motions generally need to be expanded, enlarged and used to enhance the cuts fluidity and ease. 2. Working too fast a. Forcing the tool through the wood rather than understanding how fast the wood wants to be cut with that tool and at that lathe speed. b. Cutting the wood before planning the best approach to the cut. c. Starting without an overall plan of what shape is to be achieved. 3. Cutting with the wrong lathe speed a. First projects are normally spindle projects on smaller billets of wood requiring greater RPM s to allow for smooth cutting. b. Bowl turning, starting with out-of-balance stock may require the speed to be reduced until the stock is more balanced. Then the speed can be increased to improve the cuts c. Cutting projects with voids or discontinuous surfaces required an increase in lathe speed for more cutting control. 4. Working with dull tools. a. Everyone can recognize the improvement of the cut surface and the greater ease in cutting when a tool is sharpened but few recognize when to resharpen the tool. b. Sharpening requires a light hand to dress the edge rather than grinding the tool. 5. Not recognizing that you have to pay your dues. a. Doing it again to improve lathe/tool/body operation is called practicing which few are willing to do. I suggest make one, examine what could have been done differently then do it again b. Complex project are attempted in quality wood with out doing a prototype sometimes with disappointing results. Consider making a prototype in plain wood first. c. Not making enough spindles Page 4

5 TOOL CONTROL 1 Role of the Lathe o The lathe does all of the hard physical work. It holds the wood and provides the cutting force. Role of the tool o Always select the best tool for the job and use it safely. Tools sharpness is key to safety and getting a good cut. The Turner s Role o You guide the cutting tool through the wood done with a sure, but light touch. Woodturning is not physically hard work. It s about coordination. Dancing with Your Lathe o 'Dance with your lathe' captures how we want to feel when turning. Like dancing, woodturning is about making graceful body moves. o Role of the feet. Guide the tool through the wood using your whole body and not just your arms. Using your whole body gives you more stability and is less tiring. o Spread your feet about shoulder width apart. Keep your elbows close to your side. Start a cut with your weight on one foot and gradually shift your weight to the other foot. o If the cut is too long to easily keep your balance, make two separate cuts and reposition your feet before the second cut. Moving the legs is less tiring than using your arms. It will be necessary to use only your arms for some cuts, but try to minimize these. Role of the hands. o One hand holds the tool on the tool rest (keeping it from vibrating) and aids in moving the tool forward. The other hand does most of the work. It guides the tool and determines the depth and direction of the cut. Learn to turn reverse hands, there are some cuts that must be done right handed or left handed. Making a Cut Anchor. Place the gouge on the tool rest with the flute pointing upward at a 45 angle and in the direction of the cut. Lay your left hand on top of the gouge and contacting the tool rest. All three, gouge, tool rest and your hand, must all be in contact with each other. Bevel. Using your right hand, move the tool handle until the heel of the bevel contacts the wood. This action will not cut, but will tell you exactly where the wood is relative to the tool. Cut. Using your right hand continue moving the tool handle until the bevel is parallel with the wood surface and the cutting edge engages the wood. The tool should be cutting between' 11 and 12 o'clock' as you look down on the tool. Slowly advance the tool with the left hand, remembering to steer the bevel with the right hand. 1 Tool Control was originally produced by Bill Small for the Bay Area Woodturners Association Page 5

6 Cutting Feedback o Listen. The lathe, tool and wood all give you feedback on how well you are cutting. Learn to 'listen' to the following. o Shape. You can best see the shape that you are cutting by looking at its profile against a backdrop o Shavings. If you are producing long shavings, you are shearing the fibers. Chips or sawdust means that you are scraping and will have a rougher surface. o Vibration. Vibration should be avoided. Excessive vibration may mean a loose piece of wood is ready to fly off the lathe. Vibration can also be caused by excessive lathe speed and the wood being out of round/imbalanced. o Sound. A rhythmic sound may indicate a knot, crack or other defect that should be inspected immediately. A good cut will 'sing'. Surface smoothness. Stop the lathe and inspect the surface of the wood frequently. A good shear cut will leave a smooth surface free of tear out and ridges. Tightly grouped ridges usually mean you were not cutting on the bevel. Tear out often comes from a dull tool. Use your fingers to test the smoothness. They are more sensitive that your eyes. Page 6

7 THE SRG The spindle roughing gouge is the first tool that most turners first touch and is easy to develop confidence with. With that confidence sometimes come overuse and mis-application. The SRG is named spindle roughing gouge to indicate that this tool is not for use for roughing out bowls or any hollowing application! This misuse has led to so many cases of injury that the American Association of Woodturners renamed the tool to help better define its specific application. The tool is classically ground with a square shoulder at about 45 degrees so that is can be used to turn a spindle round right up to a pommel shoulder or other square apron. The tool can be rotated to use all the edge rather than resharpening frequently. Place the tool squarely at 90 degrees to the work, hold the handle to your body and shift your weight from one foot to the other to advance along the work piece. Most problems I have noted are: 1) Failure to hold the tool square to the work leading to the tool catching a shoulder and running off in the opposite direction 2) Failure to start the cut with the handle low enough to rub the bevel resulting in tearing fibers rather than shearing them 3) Not working toward the end in a sweeping cut potentially causing a catch at the end of the work piece 4) Poor body position not allowing for sweeping, smooth cuts by transferring weight from one foot to the other 5) Holding the tool against the tool rest too tightly causing the tool to drag and jump during the cutting - not moving smoothly. Sharpening the tool is simple as placing the handle in the V arm of a sharpening jig, aligning the bevel to the face of the sharpening wheel and rotating the handle smoothly. Assure that the tool is not over-rotated which will cause the square shoulder to be rounded over. Tool size is not very important as the rounded edge can only touch the work at a single point no matter how big the tool is. I particularly like the tool from P&N as it is milled from a solid piece of bar stock rather that forged from a flat sheet of steel more mass, less vibration and more smoothness. Use it on spindles only; there have been too many snapped SRG tangs due to their use in bowl turning! Page 7

8 Gouges Deep Fluted (the bowl gouge) The deep fluted gouge is easily distinguished by longer handle and blade as well as the deeper, more massive flute. This allows the tool to be used farther over the tool rest than the shallower spindle gouge ideal for turning bowls as well as other items. Out of the box the tool may be ground with a traditional-straight across configuration favored by many English and European turners. In the U. S. the finger nail profile is preferred for its greater flexibility allowing the tool to do pull cuts and shear scraping. The finger nail profile is also referred to by many names such as Ellsworth, O Donnell, and Irish grinds. The length of the side grind, whether straight or curved, and the bevel and side angles are all a matter of personal preference. Several turners use a combination grind straight on the right side to allow shear cutting on bowl exteriors and pulled back slightly on the left side to accommodate the turning bowl interiors. When you buy a new tool don t assume these new tools are usable until you sharpen it the shape is normally for presentation only and not sharp. The exact bevel angle and the length of the side grind are, to say the least, open to active debate. Allan Batty suggests that the bluntness of the bevel should be a function of the depth of the bowl you are turning in order to keep the bevel in contact with the interior surface all the way to the bottom. The deeper the bowl - the blunter the tip bevel angle. We normally sharpen with a fixture to provide quick repeatability of our initial grind. Popular to Mny turners is the Verigrind attachment for the Oneway Wolverine system. The bevel angle is set by the angle on the Verigrind attachment and the side angle determined by the length of the Wolverine arm. The tip protrudes through the Verigrind and a constant length normally two inches. Equally useful is the Woodfast version of the Verigrind which will give the same geometry if the little ball on the tip is ground off. Page 8

9 Gouges - Shallow Fluted (the spindle gouge) Shallow fluted gouges generally are shorter handled and have a smaller, shallower cross section than the deep fluted gouges. These features allow them to be easily manipulated in working on spindles for tasks such as cutting beads and coves cuts where the tool is held close to the spindle and vibration is limited. When manufactured the depth of the flute varies and in most cases is about half way through the diameter of the shaft. Those tools that are forged have the flute held higher in the steel and can therefore can be ground into more severe angle for use in detail work. There are three typical grinds: Straight across (typically factory grind) Swept back to relieve the shoulder for more access to the work Severe bevel angle for detail work Cutting beads and coves can be the most difficult cut to learn as there are three separate motions needed to keep the bevel in contact with the wood since the surface of the work moves from horizontal to vertical as the bead or cove is cut. To keep the tool cutting properly the handle is raised as the cut deepens, the tool is rotated to keep the bevel in contact with the wood and the handle is fanned outward or inward. Three motions all at the same time! The detail is cut from left and right sides working down hill to the grain: in spindle work than means towards the center of the spindle. Cutting beads and coves symmetrically is also a challenge in order to get both faces identical. (I seem to be better at one face than the other.) The solution is practice. While shallow fluted gouges can be used for shear cutting, the deeper fluted gouges perform without vibration. Shallow fluted gouges when presented to the center of a piece of end grain and pushed straight inward toward the headstock can be used for boring holes. The left wing cut the wood and the flute extracts the chips. If the handle is slightly lowered or fanned to the rear, the tool can open up an end grain hollow form of reasonably shallow depth. Too deep and the tool is not stiff enough to prevent vibration. Page 9

10 The Skew Chisel The many types of skew chisels can be easily groups by several criteria: Oval stock Rectangular stock Straight or radiused edge I have a strong preference for the skews made from rectangular stock as I believe the oval bodied skews are too thin at the points causing excessive vibration, difficult to stand straight on a tool rest for V cuts, and are more difficult to sharpen since you can t lay them flat on the grinder. The general rule of thumb for shape suggests that the width of the bevel should be 1.5 times the thickness of the stock (shaft) and roughly at a 70 degree angle to the shaft. The tool edge on the long point side should be square and the edge on the shorter point side should be rounded over. On the radiused skews the first 20% of the edge starting from the long point should be horizontal and perpendicular to the shaft for better peel cuts (more later of the cuts). The balance of the edge than is rounded as is illustrated in the Lacer skew. Radiused skews are more forgiving for planning and beading cuts for the beginner; however the straight skews have a finer long point for better detail work. Also the straight skews will allow the long point to be more visible when making cuts. A small trick I learned from Alan Batty is to slightly chamfer the corners near the long point. This helps to prevent some of the catches than can occur when rolling a bead. It does work! For my preferences a skew of about ¾ inch width seem to be most flexible for many tasks, from cutting beads to pen turning. Wider skews work better in roughing cuts and planning cuts and on larger work such as Newell posts, chair spindles, etc. Most newly purchased skews have rather sharp corner which must be rounded over to allow the skew to slide easily along the tool rest with out digging in. The tool edge near the short point may also be radiused. This is also the one tool that to hone after grinding. First use a 600 grit DMT diamond plate to perfect the edge and then strop on a rouge-charged leather strop. Bringing the edge back usually requires only re-honing. Page 10

11 Skew chisels Part 2 There are many uses for the skew chisel stirring paint, opening cans However, the wood turners should know that there are many different uses for this tool in turning wood! The three most popular cuts are also the basis for the more advanced cut; master these, increase your productivity and more on. Peel cut The tool is laid down on its side with the long point facing the wood and the tool is rolled into the wood similarly to the use of the parting tool. This cut is very safe to perform as long as the bite size remains small. This removes a lot of wood fast but not very cleanly the cut will have to be cleaned up. If the skew is a classical straight-edged skew the resulting cut is dovetail shaped and useful for chuck tenon requiring a dovetail shape. If your skew is the Lacer-style with a radiused edge and the first ¼ horizontal the peel cut will be flat and not jagged. This tool used in this fashion can be applied to cleaning up a badly frayed knot if applied lightly and in a scraping mode. Planing cut The cut is taught to beginning wood turners as a means of cleaning up a roughed out billet and flattening out hill and valleys left by the spindle roughing gouge. For ease the tool rest is raised so that the cutting edge rests against the spindle at about 11:00 o clock. Remember place the tool against the tool rest with the bevel resting against the spindle. Raise the handle slowly to bring the front edge of the bevel into contact with the wood. Note that the handle also rotates slightly as the bevel comes into contact allow this to happen. As the handle is raised, the edge of the tool contact the spindle surface; some dust or small shavings will appear at the cutting edge. Do not raise the handle further. Lock the toll to your body and move horizontally along the spindle without readjusting your body or tool position. Page 11

12 Parting Tools For such a simple tool there are so many different kinds, shapes, widths, etc. The tool is use for separating projects from their support, establishing dimensions, making tenons, and even turning beads. Presenting the tool to the work can be either a bevel rubbing or scraping action depending on the shape of the tool and how the turner places it. Many parting tool (like examples 1 3 to the right) have a bevel below the cutting edge and should be presented as a cutting tools: rub the bevel and raise the handle to cut. This presentation will give the cleanest wood removal. With the bevel rubbing the tool also can be rolled to cut spindle beads. (Tool example 1 & 2 are also called beading and parting tools.) Examples 4 and 5 are negative rake scrapers in which the tool is pressed against the spindle fibers to be cut and pushed inwards at the center line of the project. The fluting on these tools allow for cleaner cuts by first slicing the fiber on the right and left of the cut before the center of the tool scoops out the remaining fibers. Here are some of the options: 1. The standard parting tool. The edge is square to the shaft and centered. Being a double edged tool it can cut equally well from either face. When using this tool, always make a pair of overlapping cuts to prevent the binding in the wood. Sharp edges of the shaft can be relieved to protect our tool rests. 2. The Beading and parting tool. This tool can also roll beads quite well by always keeping the bevel in contact with the wood. These tools can be used for making tenons for chucks; their extra width speeds the process of getting a flat, square tenon. Remember the overlapping cuts! 3. The diamond parting tool. The diamond shape allows only the cutting edge to be in contact with the wood. The rest of the shaft is relieved to keep the tool from binding during the cut. Be sure to sharpen equally from both sides to keep the edge in the center 4. The fluted parting tool. This tool is designed to allow the two flutes to slice through the wood while the center scoops out the waste. The expectation is that the cut will be cleaner and with less effort. Page 12

13 5. The tapered and fluted parting tool. This tool adds more mass to the thin fluted tools to stabilize it more and reduce vibrations. Being tapered to the cutting edge, the shaft is clear of the wood and should bind less frequently. Here are few hints for using this tool: Allow clearance so the tool doesn t bind. Make two overlapping cuts. As you progress alternate between these cuts to keep the tool from binding. When sharpening, keep the cutting edge square to the shaft. We want a clean parallel cut on the wood than can only be achieved with a square edge. Have two parting tools, a thinner one to part off with and a wider one to cut tenons and roll beads. Longer handles on larger parting tools allow for more support of the cut and are important when doing the one handed parting cut below. Practice parting off spindles one handed. Keep the tool shaft against your forearm for better support. If you think you can t catch the parted off piece, don t try. Reduce the tenon and then cut the work free with a saw. If parting off a spindle project, plan the work so that the parting off cut is near the headstock not the tail stock. In this orientation the work stops turning when parted off and doesn t fly away. Page 13

14 Scrapers General Scrapers are a real work horse tool. They are used to: finish cutting bowl interiors where the gouge become difficult to use complete surfacing prior to sanding make minor shape corrections to a project Do the primary cutting in hard, dense materials Most scrapers in wood turning are ground as about degrees. The burr can be left or removed depending on your intensions for soft wood the burr is retained. I personally like the biggest, thickest scraper that will fit into the project because the mass dampens vibration and stabilizes the tool. I have a collection of many scrapers that I can match the curve to the project. Some, such as the Sorby multitip has a tear drop cutter that can be rotated to different curves; its rounded shaft allows the tool to be rotated to made clean shearing cuts. With few exceptions scrapers should be used with the handle raised above center line and the blade trailing below centerline to as to prevent catches this usually requires raising the tool rest. Rotate the tool rest so that the tool while resting will be slightly skewed over to shear. Holding a scraper on edge is asking for it to be slammed down onto the tool rest with your finger in-between. Shear Scrapers Shear scrapping is the process of presenting a scraper to the wood at a skewed angle so the scraper shears across the wood fiber creating a clear cut. Shear scrapping is usually a final cut to address shape or surface problems in the wood. When preparing a shear scraper be sure to round over all edges so that they do not drag on the tool rest preventing smooth tool movement. Negative rake scrapers Negative rake scrapers are ground with a compound angle usually degrees. The cutting is due to the burr that is pushed up when the bottom side of the scraper is sharpened. The cutting is with the burr so that the tool doesn t last long and should only be used for smooth final cuts on hard woods Page 14

15 Scrapers Specialized Scrapers are the most widely varied selection of tools. The can be used for all forms of wood, ivory, plastic, and soft metal turning and shaping. This article discusses specialized form of scrapers.. Box scrapers Box scrapers are one of the most frequently used specialized tools. They are used to create straight sides, square internal corners, and flat bottoms in round boxes. Sharpening must retain the precise geometry of the tools square 90 degree corner. Beading tools The two form of beading tools are designed to assist in creating symmetrical, reproducible beads of specific sized in hard woods. The mass of wood needs to be removed first than the tool applied. Difficulties with tear out and fracturing of the wood fibers while cutting make this tool of questionable use to the experienced turner. Because of the shapes sharpening should only be done with a diamond home applied to the face of the tool not introduced into the curve shape. Captive ring tools These tools work similarly to the beading tools but are designed to shape and undercut a bead form turning it into a captive ring. As the shape is created and the tool advanced the undercut portion is reduced to zero and the ring comes free. Care must be used to work slowly and stop and sand the ring prior to completing the freeing cut. Tear out is also a problem with these tools. Dovetail scrapers These scrapers allow the turner to cut a dovetail shape on tenons suitable for use in a four-jaw chuck. Skew chisel lain down on their side accomplished the same task. In this position the skew actually is being used as a negative raked skewed scraper. Page 15

16 Deep hollowing tools Most deep hollowing tools, whether stabilized or hand held, use a small round nosed cutter of 3/16 to ¼ inch diameter. This tip is actually a metal lathe cutting tool of high speed steel formulation and can be shaped on a grinding wheel and sharpened by honing with a diamond stone. These tools are mounted in a stiff bar and worked at the centerline of the project and may be slightly canted down 1-3 degrees to reduce the possibility of a catch. Chatter tools Chatter tools are designed to do what all other tools try not to do! This is, to vibrate against the wood producing an interesting and decorative pattern. The tool itself is a piece of this springy steel held in a stiff handle and presented to the wood at a sharp down angle allowing it to vibrate. Hand thread chasers Thread chasers come in set of two, one for cutting threads internally and one for the external threads. Tools manipulation requires skill and lots of practice. The lathe needs to be able to turn smoothly at 300 RPM or even less. The courser the thread count, the more difficult the tool manipulation become. Cutting threads also requires a tight, close grain wood such as boxwood, Blackwood, etc. Page 16

17 Sharpening Gouges The reason to sharpen is to improve cut surface quality, speed project completion, and to ease amount of work we have to do. One can tell it s time to sharpen because we are pushing the tool harder, the tool heats up, the surface quality begins to deteriorate, vibration increases and the cutting sound even changes. Also assume that all new tools require sharpening and probably some reshaping also. Most of us utilize a fixture to assist us because it repeats the desired angles and allows us to return to woodturning quickly. The Oneway Verigrind/Wolverine accessories and the McNaughton, Sorby, and Woodfast all accomplish the identical tasks. The Ellsworth accessory also works well if you only want that one angle on a 3/8 th deep-fluted gouge - it is not adjustable. Mount the Oneway Wolverine attachment directly centered under the grinding wheel, square to the plane of the wheel, and flush with the front of the wheel and about 6 ½ inches below the center of the wheel. That is the same as a piece of ¾ ply under our eight-inch grinder. The Verigrind accessory is what holds the gouge and allows for the grinding of the finger nail profile shape. The projection of the tool through the Verigrind should be repeatable (2 inches in average). Tilt the Verigrind forward to the fifth notch in order to set the tip angle. By placing it in the Wolverine V-notch 6.75 inches back from the wheel face one gets good tip and side bevel angles which can constantly repeated. I have made a fixture that resets that distance exactly every time. At the right you can see that fixture and also the small block I use for setting the 2 inch tip projection. Note that the fixture must reference from the face of the grinding wheel as its diameter will change over time Sharpening should start with one side of the tool pushing lightly but firmly against the grinding wheel while raising and lowering the handle to create a radiused shoulder. Next complete to the other side in the same manner. Lastly rotate the tool from one side over the tip and completely to the opposite side. This dresses the tip. If the tip gets too pointed, repeat this last step until the tip shape is what you require. As a last thought, you should also try hand sharpening so as not to become dependent on fixtures. The time will come when the fixture will not work for you or is not available. With the grinder turned off, raise the platform to match the tip angle, and push the tool up the grinder wheel while rotating the tool to keep the side bevel in contact. After practicing a few times you can try it again on an older (and shorter) tool. For more specifics and a demonstration, go to the Oneway web site and order the fee DVD on setting up and using their lathe accessories ( Page 17

18 Stones and Grinders The purpose of sharpening is to improve cut surface quality, speed project completion, and ease amount of work the wood turner does. We need to sharpen when we are pushing harder, the surface quality deteriorates, vibration increases, the cutting sound changes or the tool heats up, and always when the tool is new. Here are a few general considerations in using your sharpening system: Keep sharpening wheels clean and true Use light touch (sharpening not regrinding) Tool should not get hot or discolored Use continuous motions for continuous edges Add good light and comfortable grinder height Use dusk mask and eye protection We prefer slow speed (1750 RPM) grinders because they heat the tools less. Grinders should be equipped with Al 3 O 2 (aluminum oxide) stones. The stone cut high speed steel (HSS) cleanly, their surfaces are friable (they chip off) leaving sharp cutting edges. The wheel color also is code to its hardness: White stones - aluminum Oxide, Al 3 O 2 o Friable surface stays sharp Blue stones - Cobalt added o Harder than white stones Pink stones - Chromium oxide added for additional hardness o Hardest, requires more pressure to use o Loads most easily and required more frequent cleaning Wheel grit most preferred 60, 80 or 120 grit. When sharpening our goals is fast, repeatable creation of a non-faceted cutting edge. The use of fixtures improves this process. For more information on fixture setup and the most common angle on tools check my website for the detailed handout on sharpening ( With a new grinder or with the addition of a replacement wheel, initial setup is very important. Check new wheel of cracks by listening for a ringing sound when striking it with a wood tool handle. If the stone is held in the center and a dull thud is heard, return the wheel for replacement as it probably has a crack and is in danger of flying apart when brought up to speed. After mounting the wheel, grinder vibration must be reduced. Rotating the new wheel to counter balance it helps. Truing the wobbly surface also is important. Note: Always wear a dust mask for these operations) Rest the diamond truing tool on the grinder s platform and lightly touch it to the wheel. The high spots will be ground down and the wheel trued to the grinder. Clean and re-true the surface with a diamond T -bar tool frequently. The gray matter that accumulates is metal debris which fouls the wheel, heats the tools are reduces the cutting action. The diamond truing tools also can flatten the surface and remove the groves that sharpening creates. Page 18

19 Principle features of a tree stem, cross-sectional (transverse) view. H CO 2 + nutrients = C 6 H 12 O 6 (Glucose) + O 2 in the presence of Chlorophyll & sunlight in the leaves The inner bark transports the glucose to where growth take place, o Roots and stem tips o The Cambium layer creates new sap wood by forming cellulose and hemi cellulose from sugars o Cellulose forms longitudinal tracheids the tubular vertical structures Lignin surrounds the longitudinal tracheids and stiffens and holds them together o Lignin is thermoplastic o Grass has no lignin no stiffness o Cotton is almost pure cellulose Transverse cells or rays transport materials between growth rings Heart wood is where the tree stores the extractives, o Lignins, waxes, tannins, gums, terpenes, oils, fats, etc Dry weight of wood is composed mostly of o Cellulose 50 % o Hemi cellulose 13 to 25% o Lignin 15 to 30% o Extractives 2 to 15% Hardwood trees o Are generally deciduous trees and drop their leaves in winter o Have a broad leave structure o Are angiosperms (seeds enclosed in a fruit or nut) o Have a more complex cell structure Softwood trees o Most common are conifers or cone bearing o Are gymnosperms producing naked seeds o Leaves are needles or scales o Generally non-deciduous Page 19

20 Wood movement Tangential Movement Radial Movement Wood species % Radial shrinkage % Tangential shrinkage Domestic hardwoods Ash, white Poplar Elm, American California laural Madrone, Pacific Maple, Silver Mesquite Oak, Live Tanoak Walnut, Black Domestic softwoods Cedar, Western red Douglas fir, Coastal Pine, Western White Redwood, Young growth Imports Bubinga Cocobolo Purpleheart Rosewood, Brazilian Page 20

21 Direction of cuts When making cuts we try to cut downhill to the grain. This is the direction in which the fibers being cut are more supported by the un-cut fibers below. The supported fibers cut more cleanly resulting in less tear out, smoother cuts and the final effect less sanding. In spindle turning down hill is towards the center of the work. In bowl turning down hill will be a function of how the blanks is oriented on the lathe. Most side grain bowls appear as indicated in the illustration. In end grain vessels the down hill cut is similar to cutting in spindle turning, e. g., towards the center of rotation. Page 21

22 Basic Shapes - Bowls Straight line Continuous negative curve. Continuous positive curve Page 22

23 Ogee curve A Ogee curve B Sung Dynasty ceramic bowl Kelly Dunn Norfolk Island Pine bowl Page 23

24 The Three-Part Bowl Cut There are many techniques for forming the interior of a bowl. It seems that each demonstrator has their own reason for why their method works better for them and why. The following technique is useful for new turners to use the bowl gouge to successfully complete the turning of a bowl. My method of instruction provides only one tool technique that is somewhat independent of gouge bevel angle, is low risk for catches, and can be used on almost any depth of bowl. There are other cuts that are added to the arsenal of techniques as a learner s skill improves; but to begin the new turners needs to master this one technique. Right hand push, Right hard pivot, Left hand push: this combined with a rotation of the right wrist between the first and second components make an easy technique to learn and is safe for a novice. Take it one component at a time: Right Hand Push This cut engages the operator with the bowl and establishes a shoulder to support the bevel and cuts down the side of the bowl. The bowl gouge is held at a 45 degree angle behind the lathe bed with the flute positioned to face horizontally away from the operator. The operator s right hand is clamped to the tool in an extreme clockwise rotation with the wrist in a vertical position. The left hand is stationary holding the tool in position. The edge of the gouge is place against the bowl interior and the right hand pushed into the bowl. The edge catches a small shoulder and the cut proceed downward. When the tool cannot proceed further the operator moves to the second part of the cut Page 24

25 Right Hand Pivot This transitions from the wall (vertical) cut to the bottom cut around the corner and into the bottom cut Without releasing the initial grip, the right hand pulls forward to a position parallel with the ways of the lathe; at the same time the wrist rotates into a more natural and comfortable forward position. The left hand remains stationary. The tool has now rotated approximately 45 with the flute facing about 2:00 o clock. What happens inside the bowl is the tool rotates to a 45 degree angle relative to the wood fibers while pivoting around the inside corner. Left Hand Push The right hand remains stationary parallel with the ways and the left hand pushes the tool away from the operator. During this portion of the cut the tool moves horizontally across the bottom of the bowl in a relatively flat cut. The flute is still facing 45 degrees to the wood fibers. The reason I have adopted this technique simplifies the tool rotation and eliminates the general concerns related to cutting the inside corner where most catches occur. The technique can be modified to make a more rounded bowl bottom by continuing to pull the right hand forward during the third phase left hand push. This pivots the tool around the left hand and creates a rounded bottom. After this technique is mastered (or at least under control) I add another interior cut. the shearing cut. Position the flute in the direction of the cut and the back of the bevel against the bowl s interior. Rotate the tool counterclockwise until the first dust of shavings appear and proceed to push the tool downward tracing the line of the cut desired. This cut produces a smoother interior and can be use as a final shaping or finishing cut. Although this cut is easy it can also be dangerous if the tool is over rotated. The exposed cutting edge becomes too open and engages along it full length and bites in very deeply becoming a catch. Page 25

26 Stabilizing green wood If you have ever turned green wood from our urban forest you have most certainly encountered issues with movement and cracking as the wood dries. As wood dries free water is released reducing the moisture content; then as cellular water starts to be released the cells begin to shrink. The wood structure also shrinks mostly radially around the ring structure, to a lesser extent tangentially across the ring structure and very little along the length of the grain. Each species behaves differently and to a greater or lesser extent. What we try to do is prevent the uneven shrinking from tearing the wood apart, generally along the medulla rays or other weak areas across the ring structure. Slowing down of the drying allows more time for the wood to move and equilibrate the internal stress and not crack. Here are several different techniques in regular use to address the problem: Stabilizing the green rough turned vessel Proper rough turning Turning to a uniform wall thickness is very important to equalize the drying. Be sure to address the tenon and foot areas which many times left too thick thus allowing cracking to occur in this area. As a rule I leave a wall thickness of 10% of the vessel diameter Proper storage Storage is important to reduce stress during the drying process. I pack the roughed out vessel with some of its own chips, then place it in a one or two brown Kraft paper bags, label, and date it. Store the vessel in a cool location which has good air circulation. As the vessel dries and begins to loose moisture you can move it to a warmer location. Typically I would start out placing the wrapped, sealed vessel on the floor in a corner and later move it onto a shelf then up the shelves to the top location. Drying can still take from weeks to months. Regularly check moisture content with a moisture meter or by regular weighing. Sealing end grain Separately or in addition, seal the end grain of the bowl or vessel to prevent more rapid drying through the open end grain fibers. Rapid end grain drying will introduce stress as the end grain dries and shrinks while side grain areas of the vessel have not moved. Wax, paraffin, paint all will work. Finish turn the vessel and add finish As an alternative complete the turning to final dimension as rapidly as possible, sand, and finish. Sanding can be difficult with wet wood as the process loads the sand paper, raises the surface temperature of the vessel and may lead to small surface fractures. Try wet sanding with water and slower lathe speeds. Finish with a penetrating finish inside and out, load the vessel until it cannot absorb more finish; wipe away the excess and set aside to in a cool airy location. Repeat until the desired finish is achieved. Now if you want to manipulate the vessel and possible speed up the process try one of the following methods: Page 26

27 Water replacement processes Pentacryl and PEG 100 (polyethelyene glycol 100) displace the free water with heavier molecules which remain in the cells preventing the shrinkage. The wood is soaked in the solution until all the water has been osmotically replaced, sometimes 2-3 months. The weight may actually go up as these molecules are heavier than the water being replaced. Finishing techniques may also be affected due by this technique. Some recent experiments suggest that soaking in denatured ethanol followed by careful drying may also reduce the loss while shortening the total drying time. Deformation is still possible. Cell rupture processes Boiling, freezing, and soap soaking all seem to allow the cells to release the cellular water more easily by fracturing the cell membrane and releasing the trapped water. The soap process is usually made of the cheapest liquid detergent cut 50/50 with water. Soaking can be from a few days to a few weeks. The seriates in liquid detergents are very similar to the material forming the fiber walls thus weakening the fiber s bonds and opening the structure and allowing water to pass through. Freezing also address the issue the cell walls since water at 4 degree C actually expands rupturing the cell walls. Freezing is done two different ways: 1) The rough turned vessel is frozen, thawed, and then turned after a day or two. 2) The vessel is frozen and left in the freezer until the frozen water has desiccated and the vessel is dry. Some shape change takes places but the cracking is reduced. Desiccation is a function of the size of the vessel and will take months. It s like evaporating ice cubes. Green wood turning is inexpensive, forgiving to the tools, and with the wood movement exciting. Remember: wood is cheap Page 27