A chatter tool is nothing more than a small, round-nose (or sometimes V-shape) scraper made from thin stock that vibrates when the tool is brought into play. The vibration creates interesting decorative patterns that are cut into end grain. The tool is often used to put decorations on box lids and to add fun embellishment on knobs. However, the technique only works on end grain of fairly substantial wood.
The thin stock is mechanically clamped in a substantial handle. The frequency at which the tool resonates is controlled by how far it is extended out of the handle and by the speed of your lathe. Short extensions and greater speeds result in high frequency and vice versa. To get the right pattern, you need to fiddle with the extension of the tool from the handle and with the lathe speed. You can also change the pattern by presenting the tool in different locations-above center, on center, and below center. Presenting the tool on center gives straight chatter marks, while positioning it above or below causes the pattern to swirl in opposite directions. The tool is readily available in woodworking-supply catalogs, but it’s easy to make a shop-built version.
The classic way to cut screw threads in the lathe is by chasing, which requires a lathe that can be taken to very low speed and a set of chasers. Chasers are sold in sets: one for internal threads and one for external. Years ago, they were offered in just about any thread pitch imaginable, but today they are only offered in 16, 1 8, and 20 pitch. For most wood situations, 16 or 18 is about right. Chasers are available from Craft Supplies.
In the past, threads were just as likely to be chased in bone, ivory, or horn because turners used these materials often. Chasing requires wood of exceptional properties, such as boxwood, dogwood, persimmon, pear, or, in a pinch, maple. Many tropical species also work well for chasing. All of these woods are exceptionally dense and tight-grained, allowing threading without crumbling along the grain.
The business end of a chaser looks much like a thick sawblade except the teeth are angled at the pitch angle of the thread to be chased. The trick to using a chaser is to set the lathe to a very low speed (5 rpm to 10 rpm) and tip the scraper up so that the angled face (edge of the teeth) engages the wood but the actual cutting edge is clear of the cut. Because the teeth are at the pitch angle of the thread, the tool will move sideways as the work turns. You need to apply a firm inward pressure (or outward pressure for internal threads) to chase a deep line in the area to be threaded. Additionally, you must apply some sideways force to make the chaser cut at the correct pitch.
Next, return the chaser to the beginning of the thread, and pick up the lines that you have previously incised. The instant the thread is picked up, tip the tool down to bring the edge into play in a scrape cut (see the photo above). Again, some sideways pressure is necessary to maintain pitch. Return the chaser to the start and repeat the process until a perfect thread is formed. Internal threading is more difficult because you cannot easily see what is happening.
If you are threading to a shoulder (as in boxes), redrawing the chaser at the precise moment is also required. In other words, very low speed is a must. For those lacking a variable-speed lathe, an old trick for this kind of work is to mount the motor on a swing arm controlled by a foot pedal. Pushing down on the pedal lifts the motor and slackens the belt. Releasing the pedal drops the motor and tightens the belt, giving normal power. This allows fine nuances of power and speed. Often a spring or counterweight provides proper belt tension during normal use, but this scheme only works with V-belts.