Tip #56
Lathe Turning
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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
Select a gouge and lay it across the left end of the tool rest. The cup should face up and slightly toward the right end of the tool rest. The shank and handle should be pointing down and angled slightly toward the left end of the tool rest. Gently feed the cutting edge toward the stock until the tip just touches the stock. Then draw it slowly and steadily along the tool rest to the right, removing a little bit of the stock (Figure 12-25).

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
Once the stock has been rounded, “size” the stock, marking the various diameters of the beads and coves you want to cut.

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
When you've marked the positions and diameters of the various parts of your design, begin to cut the shapes. Usually, it's easiest to start with the convex curves or beads.

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
It's much easier to sand a turning on the lathe than it is to remove it and hand sand it. However, since you have to get your fingers right next to the spinning stock, you must be extremely careful.

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
After the spindle is sanded, part the spindle from the waste stock. Using the parting tool turned on its edge, scrape away stock from either end of the spindle until the diameter is as small as it can safely go and still not break (Figure 12-36). Warning: Never part the stock completely or turn the spindle down to such a small diameter that it snaps on the lathe. Always remove the spindle from the lathe and finish cutting off the waste stock with a saw (Figure 12-37).

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