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Lathe
Turning
Right
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1-23, 8788KB) Lathe turning is perhaps the only woodworking operation in which, after stock is cut to size, you can start and finish a project in just one mode of the Mark V. But it also demands a good deal more skill and patience than other opera-ations. If you're just beginning, don't be discouraged. Turning takes a little practice, but once you get the hang of it, it's one of the most satisfying woodworking techniques.
The lathe hasn't changed in principle since it was a primitive, bow-powered tool that is said to have been invented in ancient Egypt. It remains a means of turning stock at controlled speeds so sharp tools may be pressed against it, shaping it symmetrically. Electric motors have replaced the various hand powered or foot powered devices originally used, but the quality of the output still depends on the operator's skill in manipulating the chisels used to form the stock. There are two basic kinds of lathe turning: spindle turning and faceplate turning. Spindle turning is turning stock between two centers--the drive center and the cup center (Figure 12-1). Usually the end product is a long cylinder, like a table leg or a candlestand.
Faceplate turning is turning with the stock mounted to a faceplate (Figure 12-2). This faceplate is, in turn, mounted to the main spindle. The end product is usually shorter and wider than spindle turning, like a platter or bowl. Shopsmith offers two faceplates, 3-3/4" and 6" in diameter.
Setup and Features To set up your Mark V in the lathe mode, follow the instructions in the Owners Manual that came with your machine. As you work in the lathe mode, you'll find that the Mark V is an extremely capable lathe with several special features.
Lathe Tools
There are four basic tools that you need when doing lathe work (Figure 12-3).
A basic lathe tool set includes 1" and 1/2" gouges, a 1/2" round-nose chisel, a 1" skew chisel, and a 1/8" parting tool. These five tools can be used for all types of turning.
Holding Lathe Tools
Two ways to grip lathe tools properly (reverse if left handed) are demonstrated in Figure 12-4. The left hand is usually placed on top of the blade, with the little finger toward the stock. The butt of the hand or little finger rides against the finger ledge. The right hand holds the handle of the tool and provides the movement which determines the cut. The part of the hand that rests on the finger ledge also acts as a gauge. An alternate method of holding the lathe tools consists of placing the left hand on the blade with the thumb on top. The back of the hand rests on the finger ledge and the fingers are placed comfortably around the tool or on the finger ledge. The right hand serves the same purpose in this holding method as it does in the method mentioned previously. When making smoothing cuts or when roughing stock to size, the tool may be moved along the tool rest parallel to the work, taking a bite that remains constant because the left hand butts against the tool rest ledge and acts as a control. The feed of the chisel, which determines the amount of wood removed, should be slow and steady--never forced, never jabbed into the work. After the tool is in position, start the cut by advancing the tool slowly until it touches the wood.
Three Cutting
Actions Scraping--Scraping is the easiest and safest of the three actions and the best for the beginner to use. Many experienced operators use this action almost exclusively because it gives good results.
A scraping action with a round-nose chisel is shown in Figure 12-6. Notice that the hand position hasn't changed except for the fingers. Placed as shown, the thumb and forefingers do most of the gripping and help to bring the cutting edge of the chisel close to a horizontal plane. This position is maintained while the chisel is advanced to the depth of the cut and then moved slowly from side to side to increase the cut's width if necessary. Full depth does not have to be reached at once. The chisel may be moved forward a slight amount and then moved from side to side as the pivot point is maintained. The procedure is repeated until the full shape is formed. Each “pass” removes a little more wood. Cutting--This action calls for bringing the tool edge into the surface almost as if it were a knife. The feed should be slow and the cut should be light. Warning: If you jab the chisel into the work-piece suddenly or deeply, the chisel will be wrenched from your hands. You could be seriously injured. At the very least you will ruin the workpiece by cutting and lifting a large splinter from it. Don't use the cutting action until you have practiced enough with the scraping action to be thoroughly familiar with each tool and what it can do. Once you have become proficient with the cutting action, you'll find that it leaves a surface smooth enough to finish with a little touch-up.
Shearing--The shearing action is usually limited to the skew and gouge. It is a cutting action with the tool edge moved parallel to the work, taking a constant bite, shearing away a layer of wood from the surface of the stock. A shearing action with the gouge is illustrated in Figure 12-7. The shearing action of cutting beads with a skew is shown in Figure 12-8. Shearing a cove is one of the easier cuts. Since the tool is held on edge, move your thumb behind it to steady it while making the cut. When the gouge is sharp and properly held, wood is removed rapidly and the surface is left smooth.
While each of the tools does certain operations better, the overlap is so great that no hard-and-fast limitations can be set down for each one. Each tool will cut differently, depending on the action, the angle, and the way it is moved. Practice with each tool until you have the feel of each of them. When you arrive at this point, habit will take over and your use of the tools will become an individual application that is standard with you.
Using the
Gouge It is the only tool to use when doing initial rounding (Figure 12-10). This is essentially a shearing cut with the gouge held on its side and moved parallel to the work. Depth of cut is maintained by a finger resting against the tool rest ledge.
Rounding should be started somewhere along the length of the stock with the gouge moved in the direction indicated by the arrows in Figure 12-9E. You'll find it is easier to work from a midpoint toward each end of the stock instead of making one continuous cut from end to end. To make rounding cuts in a limited area, use the gouge between sizing cuts made with the parting tool or marks penciled on the workpiece.
Figure 12-11 shows how you can use the gouge in a scraping action to form a cove whose size and shape is dictated by the tool. The gouge is held in a horizontal position and slowly moved directly forward. Warning: Do not remove too much material at once. Retracting the gouge frequently will allow waste material to fall away.
The shearing action is a more advanced way to form a cove with the gouge. Begin with the gouge on its side as if you were preparing for a rounding cut. Feed the gouge forward to contact the stock; then rotate it on the tool rest as you move it toward the center of the cove (Figure 12-12). Work this way from both sides of the cove toward its center. As the gouge is manipulated, the action changes from shearing to scraping (Figure 12-13), which occurs at the full depth-of-cut point only.
Using the
Skew Chisel
Typical applications of the skew chisel are shown in Figure 12-14. While professionals use the skew mostly in a shearing action, it can function efficiently while cutting or scraping. A common scraping action is shown in Figure 12-14E with the chisel held to square off the end of a cylinder. When held this way, the chisel's sharp point removes material quickly and leaves a reasonably smooth surface. The same result is obtained by using the point of the skew in a cutting action (Figure 12-14B). When used this way, the skew works like a knife, severing wood fibers and leaving a surface that requires little sanding. Tapers are formed by starting the cut with the heel of the blade and raising the handle as you slide the chisel along the tool rest. To smooth a taper that was formed with another tool, use the skew as shown in Figure 12-14A or F. This can be a scraping or a shearing action. If you move the skew so only its heel contacts the work-piece, it will shear. If you position the skew so its edge is parallel to the workpiece and then advance it while maintaining tool-to-work-piece contact, the action will be scraping. Probably the smoothest surfacing cut of all is shown in Figure 12-14H where a shearing cut is being used to smooth a cylinder. The cutting edge of the skew is held at an angle to the longitudinal axis of the workpiece. When done correctly, the surface of the work-piece is smooth with a finish that looks burnished. It will take practice.
The skew is used to form beads. Like a cove, the bead requires three marked or imagined dimension lines: one to indicate the bead's center and one on each side of the center to indicate total bead width. Start by placing the heel of the skew lightly on the bead's center-line so its edge is tangent to the curve you want to form. Move the skew into the workpiece. At the same time, rotate and lift the handle to follow the curve of the bead. It will take several passes to form one-half of the bead (Figure 12-15). Follow the same procedure, but work in the opposite direction, to form the other half of the bead (Figure 12-16).
Using the
Roundnose Chisel
Using the
Parting Tool The parting tool is often used to determine the depth of cut or the diameter of the final shape. To speed up the procedure when making preliminary sizing cuts, handle the tool as shown in Figure 12-19. Start with the tool horizontal, then slowly raise and lower its cutting edge as the cut deepens.
Planning the Design Before you attempt to form a turn-ing, you must first plan the design. Otherwise you may end up with an unattractive project. The best way to plan the design is to draw a full-size plan with the shapes and dimensions marked, so that before you start you will know exactly what shapes you are going to cut and where. Here's an example of how to plan the design for a spindle turning 12" long and 3" in diameter: Draw a rectangle 12" by 3" on a piece of paper. Draw a centerline down its length. Break up the length into design areas by draw-ing horizontal lines that are proportional and pleasing. Let the base design occupy the bottom 3"; use 7" for the transition from base to top and leave the remaining 2" for the top.
Lathe Safety Warning: Before using the lathe, read and understand these important safety instructions: Danger Zone--The danger zone on the Mark V in the lathe mode changes as the turning progresses. Before the stock has been rounded, the danger zone extends 3" out from the stock in all directions. After the stock is rounded and while it's being shaped, the danger zone extends 1" out. After the stock is completely shaped and the tool rest has been removed, you can safely put your hands near enough to the workpiece to sand it on the lathe. Always keep your fingers and hands out of the danger zone. When you work at the lathe, be careful not to touch the stock as it turns, until you have finished shaping it. In particular, be careful not to let your fingers or hands slip between the workpiece and the tool rest. Keep both hands on the tool you're using and in front of the tool rest. Before sanding your workpiece on the lathe, turn off the machine, let it come to a complete stop, and remove the tool rest. Balance--This is extremely important when turning glued-up stock, long stock and stock more than 3" in diameter. Check the balance of your spindle and face plate stock after you've marked the centers. To do this, drive a standard 8 penny nail straight into each center.
Use suitable string to hang the stock in a level position from the front bench tube of the Mark V or a saw horse. The ends of the string should be looped around the nails (Figure 12-20). Gravity will pull the heavy side down. Use a jointer, bandsaw or hand plane to remove no more than 1/32" at a time from the heavy side until the stock re-mains stationary when rotated to three positions 90 degrees apart.
Lathe Speeds Before you mount stock on the lathe be sure the speed is set at “Slow.” After the stock is mounted, turn on the machine, set the speed dial to the proper speed and let the lathe come up to speed. The operating speeds for lathe turning are determined by the size of the stock you're turning and the operation you're performing-whether you're rounding the stock, shaping it, or finish sanding. Generally, you can use slightly faster speeds as you progress from rounding to shaping to sanding. You can also use slightly faster speeds with smaller stock. The larger the workpiece, the slower the speed should be for each operation. To help determine the right speed for the job, use Table 12-1.
Spindle Turning All spindle turning projects involve these six basic steps: 1. Mounting. Mounting the stock on the lathe is an extremely important operation. Warning: Improperly mounted stock is dangerous and difficult to turn. 2. Rounding. The first step is to turn the stock down to a rough cylinder. 3. Sizing. Once the stock has been rounded, mark the positions of the shapes you want to make and turn them down to their approximate diameters. 4. Shaping. Turn the beads (convex curves) and coves (concave curves) in your design. 5. Sanding. After the stock is shaped, remove the tool rest and sand the workpiece smooth. 6. Parting. After the final sanding, reinstall the tool rest and remove the waste stock (if any) from the turning. Mounting
To mount stock between the lathe centers, you must first find the center of the stock. To find the center of a square workpiece, use a straightedge and draw two diagonal lines on each end of the workpiece, from corner to corner (Figure 12-21). Where these two lines intersect marks the center of the stock. To find the center of a round workpiece, use a center finder. With a plastic or rawhide mallet, seat the drive center in one end of the workpiece and the cup center in the other.
Caution: Do not hit the centers with a metal hammer-you will ruin them. Position the center point at the center mark; then hit the center sharply (Figure 12-22). When properly seated, the drive center will leave four slots where the spurs bit into the wood. The cup center will leave a small circle (Figure 12-23). Warning: The spurs of the drive center and the circle of the cup center must penetrate into the wood at least 1/16" in order to mount the stock securely on the lathe.
If you're working with hardwood, drill 1/8" diameter holes, 1/2" deep in the center of both ends of the workpiece, and saw diagonal kerfs 1/8" deep. This will help seat the drive center. If the workpiece you're turning is more than 3" square, cut off the square corners to form an octagon. This will make the workpiece safer and easier to turn. Use a bandsaw or table saw to cut off the corners. Mount the drive center on the main spindle and the cup center in the tailstock. Position the power plant so that the centers are about 1" farther apart than the length of the workpiece, and lock the power plant in position. Warning: Be sure the speed dial is set on “Slow.”
Wax or soap the end of the stock that mounts to the cup center to help it turn smoothly. Hold the stock against the cup center; then extend the quill and mount the other end on the drive center. Press against the quill feed lever to be sure both the spurs and the cup are engaged. Do not release the tension. Then lock the quill in place (Figure 12-24). Adjust the height of the tool rest for scraping or shearing, whichever you prefer. Then align the tool rest parallel to the stock within 1/8" to 1/4". Be sure the setscrews in the tool rest assembly are secured. Turn the stock by hand to be sure it clears the tool rest. Make a five-point check. All five locks--power plant, carriage, tool rest height, quill and tailstock--should be secure. The speed should be set at "Slow." Turn on the Mark V. The stock should rotate smoothly, without excessive vibration.
Rounding
To reverse the cutting action, turn the gouge so the cup still faces up but slightly toward the left end of the tool rest. Feed the gouge into the stock and draw it back along the tool rest to the right. Repeat this procedure until the stock is completely round, without any flat spots.
To tell if there are any flat spots without turning off the machine, carefully let the shank of the qouge rest on the revolving stock (Figure 12-26). If the gouge vibrates or jumps up and down, the stock is not quite round. Warning: Round all stock at “Slow” speed and never remove too much stock too quickly. Sizing
Use a pencil and a parting tool for this operation. With the pencil, scribe lines on the revolving stock to indicate where you want the beads, coves, and other parts of your spindle design to begin and end (Figure 12-27).
With a parting tool, cut grooves in the workpiece to indicate the position and diameter of the different shapes in your design (Figure 12-28). To gauge when you've reached the proper diame-ter, set a pair of "outside" calipers at the desired measurement and test the diameter where you're cutting from time to time. When the calipers just slip over the stock at the bottom of the groove, you've arrived at the desired diameter (Figure 12-29). Shaping
Select a skew chisel to round the sides of the beads. Feed the edge of the chisel slowly into the stock; then move the handle of the skew from side to side as needed to shape the bead (Figure 12-30). After you've made the beads, begin to cut the coves, the concave curves in your design. Select a gouge and slowly feed it into the workpiece, gradually removing stock. As you did when you were shaping the beads, move the handle of the tool from side to side to shape the cove the way you want it (Figure 12-31).
When forming duplicate pieces, for example, chair or table legs, it's better to work with a hardboard template (Figure 12-32). The template is a full-scale, half-profile of the part and can be used to check the turning as you go, as well as for marking initial dimension points. Although woodworkers usually rely on skew chisels to cut beads and gouges to cut coves, you can use other tools if you wish. Select whatever seems best for you. Sanding
When the turning has been completely shaped, turn off the machine and let it come to a complete stop. Warning: Remove the tool rest before sanding a turning on the lathe. Turn on the machine and slightly increase the speed of rotation. Starting with medium (80#) sandpaper, begin to sand the spindle by holding the sandpaper lightly against it (Figure 12-33). Double the sandpaper over several times for two reasons: The paper heats up quickly and extra layers of paper protect you from being burned. Also, the extra layers of paper keep your hands from contacting the rotating spindle. Work your way through progressively finer grits of sandpaper until you get the spindle as smooth as you want it. Warning: Never wrap the sandpaper entirely around the spindle or allow strands to wrap around the spindle. The spindle will grab the sandpaper or strand and draw your fingers into the rotating spindle.
Because sanding a spindle on the lathe usually requires you to sand across the grain, tiny “feathers” will develop on the surface of the spindle. There are two ways to remove these. The easiest is to wet the spindle with a damp rag, wait a few minutes for the water to dry and raise the wood grain, then give the spindle a final sanding with a very fine grit sandpaper. If you don't want to wet the wood, turn the Mark V off and dismount the spindle. Remove the centers and seat them in opposite ends of the spindle. Remount the spindle, putting enough pressure on the quill to engage both the drive center and the cup center. This reverses the rotation of the spindle so that you can remove any microscopic feathers with a light sanding.
Here are several other lathe sanding tips: The Mark V sanding disc is a super tool to use when smoothing uniform cylinders or tapers (Figure 12-34). Another trick used by professionals is shown in Figure 12-35. After the workpiece has been smoothed by sanding, hold a strip of wood against the workpiece as it is turning. The result will be a hard, burnished surface that is fine for a natural finish but will not take a stain.
Parting
Faceplate Turning Faceplate turning is similar to spindle turning in some respects, but very different in others. We'll point out those differences as we go through this basic procedure. As with spindle turning, faceplate turning also involves six basic steps: Mounting, rounding, sizing, shaping, sanding and parting.
Mounting
If you don't want screw holes in the bottom of your finished project, you can mount the turning stock to another block of wood; then mount this block to the faceplate. Select a scrap block at least 1" thick and about the same diameter as the faceplate you'll be using. Find the center of this scrap block; then glue the block to the turning stock, center-to-center. Put a piece of paper (brown craft paper or grocery sack) in between the block and the turning stock (Figure 12-40). Warning: Leave the pieces clamped for at least 24 hours prior to turning. Later on, this paper will make it easier for you to part the scrap block from the turning. After the glue has set up com-pletely (at least 24 hours), mount the scrap block to the faceplate with three #12 x 1-1/4" wood screws. Warning: Be sure the screws penetrate into the block at least 3/4". For large, bulky faceplate turnings use longer screws and a thicker scrap block.
Be sure the speed dial is set on “Slow.” Then mount the faceplate on the main spindle of the Mark V (Figure 12-41). Position the tool rest to turn the outside of the workpiece first. When the tool rest is properly positioned and the set-screws secured, turn the work-piece by hand to make sure it doesn't scrape against the tool rest. Make a four-point check. All four locks -power plant, carriage, tool rest height, quill-should be secure. The speed should be set at “Slow.” Turn on the Mark V and slowly turn the speed dial to the recommended speed for the operation. The stock should rotate smoothly, without excessive vibration.
Rounding
Sizing
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