The Action and Uses of a Tom Thumb Bit

A Tom Thumb bit hanging on a green synthetic bridle.
K. Blocksdorf

A lot of equestrians erroneously consider a Tom Thumb bit to be a mild snaffle bit. However, the Tom Thumb bit's jointed mouthpiece doesn't actually make it a snaffle—it's actually a leverage bit. The Tom Thumb bit is a more severe and uncomfortable bit than many people realize.

In unskilled hands, this particular tool can be quite a harsh bit, which can cause your horse to object because of the discomfort it causes. Because of that, the horse might appear to misbehave, which is dangerous for the rider and the animal.

The Appearance of a Tom Thumb Bit

Tom Thumb bits have a jointed mouthpiece and medium-length shanks that range from 5 to 7 inches long (15 to 18 centimeters). The headstall of the bridle attaches to the rings at the top, and a curb chain or strap attaches to the D-shaped slots.

There are several types of mouthpieces found on Tom Thumb bits, including various types of rubber and synthetics, rollers, and copper or copper-inlaid strips. These bits have shanks, although they are shorter than many western bits, but nonetheless making it a leverage bit. Leverage bits means that every pound of pressure that the rider puts on the reins, the horse will feel that pressure times three.

The curb chain is a very important part of this (and all) curb bit, and should always be adjusted properly. A curb strap of leather or synthetic material might be used instead of a chain to prevent the bit from rotating in the horse’s mouth too far.

The Uses of a Tom Thumb Bit

Many horse enthusiasts disagree on the severity of the Tom Thumb bit. Because it is jointed, it has a nutcracker action in the mouth. Combined with the leverage action provided by the shanks, the bit will apply pressure to the horse’s head over the poll and under the chin as the curb chain or strap pulls upward. If the reins are pulled hard, the joint in the mouthpiece bends and can come in contact with the roof of the horse’s mouth. This can cause the horse to toss its head, which is not safe.

Using a Tom Thumb Bit Correctly

The Tom Thumb is labeled as a bad bit by some, but like any bit, it depends on why it is being used, and the skill of the user. Tom Thumb bits are most commonly used by young or small riders who are trying to manage a stout, insensitivie horse.

For experienced riders, if the Tomb Thumb bit is being used to make your horse stop faster, you might consider why your horse isn’t stopping in the first place. Although a bit might make your horse stop faster in the short term, a horse will learn to ignore the bit, just as it has the previous bit it wore and will need another stronger bit down the road. Instead of amplifying the rein aids with a longer shanked curb bit or another type of bit, it’s often better to train both the horse and the rider.