Mounting a Work on Lathe Chuck (I)

Now that you have your lathe set up and running, it’s time to think about turning something. But first you need a way to hold the work in the lathe. I’ve always maintained that I can turn anything, if given a way to mount it in my lathe. This is where chucking comes in. Technically, a chuck is any device that holds work in the lathe. It can be a set of centers, a faceplate, an elaborately manufactured jawtype chuck, or a simple shop made glue block.

Understanding the difference between spindle turning and faceplate turning is central to the concept of chucking. In spindle turning, the grain of the wood being turned runs between the centers of the lathe, that is, parallel to the axis of the lathe. In faceplate turning, the grain of the work runs at right angles to the axis of the lathe. Although turning between centers is commonly associated with spindle turning, it’s possible to hold work this way and yet be faceplate turning. Similarly, it’s possible to have something screwed onto a faceplate and still be spindle turning. The screws in this case would be into the end grain of the wood. Remember that the orientation of the grain, not how the work is held, dictates the type of turning. Each type of work also requires different tools and turning techniques.

Centers

The oldest and simplest way to hold work in the lathe is between a set of centers, one mounted in the headstock and the other in the tailstock. Most spindle work is held this way. Centers are a fast and reliable way to mount work, and they allow unlimited chucking and unchucking, which is an advantage when you want to trial-fit turned furniture parts or to allow stains and finishes to dry between lathe operations.

DRIVE CENTERS

The drive center, or spur center, mounts in the headstock spindle. It both holds the work and transmits power to it. Except on very inexpensive lathes (where the center screws on the headstock spindle), the shank of the center is a Morse taper that fits into a matching socket in the spindle. The business end of the center is a small central point surrounded by spurs (also called tines). The central point should protrude 1/16 in. to 1/8 in. beyond the face of the tines to ensure centering of the work before the tines bite in. On better drive centers, the central point is removable and adjustable for the amount it stands proud of the tines.

Drive centers are sold in two-spur and four-spur models. A two-spur center is generally better because it drives as well as a four-spur one and can be oriented to give positive drive no matter what the contour of the end of the turning billet (see the illustration on the facing page). If the surface is irregular, a four-spur center will drive on only one tine, which can cause the work to go off-center and even kick out of the lathe in extreme cases. If your lathe comes with a four-spur center, you can easily modify it by grinding away two of the tines. Mini centers are also available, which are used where a small footprint is desired, as in the turning of a knob. The diameter of the tines is so small that minis are much less sensitive about how square the end of a billet is.

If the billet end is not square, a four-spur d rive center d rives on only one tine and the work constantly walks off-center. A two-spur center can be turned to drive on both tines, eliminating the problem
If the billet end is not square, a four-spur d rive center d rives on only one tine and the work constantly walks off-center. A two-spur center can be turned to drive on both tines, eliminating the problem

Each tine of a spur center comes to a chisel edge. These edges must not be in line with each other or the center will become a wedge and split the work. If the tines become dull or damaged, you can grind them back to a chisel edge, making sure you grind on the bevel side only. You should also keep the central point sharp. If it is removable, it’s easy to sharpen it by mounting it in a cordless drill and simply touching it to a running grinder.

A two-spur center (far left) drives just as well as a four-spur model (second from left). A mini center (second from right) is necessary when a delicate footprint is desired, such as when turning very small spindles, pen blanks, and the like. The center at far right is typical of those supplied with economy lathes; it is built on a short Morse taper.
A two-spur center (far left) drives just as well as a four-spur model (second from left). A mini center (second from right) is necessary when a delicate footprint is desired, such as when turning very small spindles, pen blanks, and the like. The center at far right is typical of those supplied with economy lathes; it is built on a short Morse taper.

It’s normally not necessary to pound the center into the work or to saw lines in the end of the billet, as some turners recommend, to achieve positive drive. Pressure from the tailstock is generally sufficient to drive the tines into the work. Even on small lathes, there is tremendous mechanical advantage in the screw-thread mechanism of the tailstock handwheel.

Place the center-punched end of the billet on the center pin of the steb center, and catch the other center-punch mark with the tailstock center. Once you tighten the tailstock, the work is securely held.
Place the center-punched end of the billet on the center pin of the steb center, and catch the other center-punch mark with the tailstock center. Once you tighten the tailstock, the work is securely held.

It’s a good idea to grind a nick on the outer radial surface of one of the tines. Whenever you remove work from the lathe but plan to rechuck it, make a pencil mark on the workpiece next to the nick so you can reposition it accurately. With wear, sharpening, and mishaps such as drops on concrete, each tine gets to be a different length. Unless the work is repositioned on the drive center exactly the way it was removed, perfect centering will be difficult. Your pencil mark and nick make rechucking simple.

Steb centers are great for furniture work where the ends are cut square because they allow you to stop the work without stopping the lathe simply by easing the tailstock pressure.
Steb centers are great for furniture work where the ends are cut square because they allow you to stop the work without stopping the lathe simply by easing the tailstock pressure.

Standard drive centers are available in Morse-taper sizes #1, #2, and #3. If you plan to turn miniature work such as dollhouse furniture, a standard drive center is too large and will get in the way. The solution is to buy a mini drive center, which has a smaller outside diameter ranging from 3/8 in. to 1/2 in.

To inspect your work, simply loosen the tailstock a bit and place your open hand against the spinning billet. It will stop instantly. To continue with your work, tighten the tailstock again.
To inspect your work, simply loosen the tailstock a bit and place your open hand against the spinning billet. It will stop instantly. To continue with your work, tighten the tailstock again.

Lately my preference in drive centers for turning furniture parts has become steb centers, which feature a serrated ring with a spring-loaded central point. I center-punch each end of my billets and place the mark on the center point of the steb center with the lathe running. I catch the punch mark at the other end of the billet with the tailstock center and advance the tailstock so that the work catches securely and turning progresses normally (see the top photo at right on the facing page). The great advantage is that I don’t have to shut off the lathe to check my work. I just loosen the tailstock a tad and the center point pushes the work off the serrated ring. I touch the work lightly and it stops dead (see the bottom photo on the facing page). After inspection, I simply tighten the tailstock and instantly start turning again. It is easy and much quicker than stopping and starting the motor.

Steb centers come in 1 in. and 1/2-in. sizes, which are measured by the diameter of the serrated ring. I would not work without either. The ½ in. steb center handles normal-sized furniture parts well, while the 1/2 in. size is perfect for knobs and other small items. A steb center only works well on prepared billets (with square ends) of reasonable size; a 3-in. square table leg is about the biggest it can handle. If work is taken off of the lathe, rechucking is much easier with a steb center because it tends to center more accurately than a normal drive center.

TAILSTOCK CENTERS

The tailstock center, which mounts in the tailstock spindle, centers the work and exerts force through itself to the drive center in the headstock. It also gives radial support to the work, thereby holding it in the lathe. As with drive centers, the tailstock center has a Morse-taper shaft, but the business end is quite different.

There are two types of tailstock centers: dead centers and live centers. The simplest dead center is a 60° point, but the more traditional design-a cup center-consists of a simple pivot bearing surrounded by a raised ring. Because the center is stationary, it needs to be lubricated to reduce friction and heat buildup from the rotating workpiece. Any grease will do as a lubricant-I once used butter from a high school cafeteria to get me through a demonstration. No matter what the lubricant, you can expect some burning with a dead center. The benefit of a cup center is that the ring around the point retains grease, so lubrication is better and makes the work less prone to splitting.

There is one advantage to using a dead center: You can touch it with a tool (lightly) and it will not dull the edge as a live center will. Occasionally a turning situation, such as when you have to turn around the end of the billet right up to the center, makes a 60° dead center worth using. Dead centers are inexpensive, and lathes have traditionally come with a dead center in the accessory kit.

Live centers are a great improvement over dead centers because the center point is mounted on a ball bearing and rotates with the spinning work, eliminating the need for lubrication and the risk of burning. In addition, you can exert much greater force on the work with a live center, which means that the work is held more securely. Because of these overwhelming advantages, even entry-level lathes generally come with a live center in the accessory kit these days. Unfortunately, it’s typically not a very good live center-in fact, you often would be better off with a dead one.

At far left is a typical economy live center supplied with many lathes. The next four are ful l-featured live centers with four points (left to right): a cup; an extended cup; a core center, which can be d riven into a Y2-in. hole on very long and heavy work; and a 50-degree point mounted in the center. Second from right is a heavy-duty center by Oneway, which is a normal cup point as shown, but by attaching the cone at the far right it will center large bores or, when reversed, go over squares, hexes, and such.
At far left is a typical economy live center supplied with many lathes. The next four are ful l-featured live centers with four points (left to right): a cup; an extended cup; a core center, which can be d riven into a Y2-in. hole on very long and heavy work; and a 50-degree point mounted in the center. Second from right is a heavy-duty center by Oneway, which is a normal cup point as shown, but by attaching the cone at the far right it will center large bores or, when reversed, go over squares, hexes, and such.

Better live centers are sold with two or three interchangeable points. The 60° point and cup center are standard designs, and some live centers also come with a third flat-faced insert (see the photo above), which is used for special tasks such as holding a bowl in a jam chuck or spinning metal.

Faceplates are offered in a wide variety of sizes and qualities.
Faceplates are offered in a wide variety of sizes and qualities.

The idea behind the cup center is that the outside ring prevents the work from splitting. In my experience, a 60° point has no greater tendency to split work than a cup point. What’s more, it holds in a much smaller area, which allows you to turn nearly the center of the billet, and wears much better in service. For these reasons, the 60° point is the only point I give my students. You can often get 60° live centers from metal working supply houses at bargain prices. Even though these centers are designed for metalworking lathes, they work fine for woodturning. The one time a cup point center is necessary is when chucking split turnings. Split turnings have a paper joint in the middle and would be split prematurely by a 60° center.

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Author: Aliva Tripathy

Taking out time from a housewife life and contributing to AxiBook is a passion for me. I love doing this and gets mind filled with huge satisfaction with thoughtful feedbacks from you all. Do love caring for others and love sharing knowledge more than this.

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