Tom Thumb Western BitThumb Tom Western Bit
Nearly all of them open their mouths and try to avoid the stress and pains. Genuine bridle is a "direct compression " bit (as distinct from a lever bit), i.e. the bridle is placed directly opposite the bit mouths, which allows it to come into close proximity to the edges of the horse's jaw. A poun of pulling on the bridle produces a poun of compression on the side of the horse's throat.
The chisel has a shaft that extends above and below the nose piece, with the reigns fixed at the bottom of the shaft. Pulling on the shaft produces a lever action with the horse's jaws as the pivot point. of the chisel determines the amount of lever action generated.
When there is one in. above the nose piece and two in. shaft below the nose piece, the bit has a relationship of one to two; a pounce of traction generates two pounces of stress on the horse's muzzle. With a lever action the horses feel pressures on the cheek, jaw, mouth and taste buds.
If I used a Tom Thumb, the only times I would ride with a small kid is on a big, unsensitive stallion that needs the additional lever effect. I' d suggest using a normal bridle or side drag, or if you need a little additional braking, try a kimber vetch.