People argue that more teeth on a ratchet mean more turning torque. It is correct, but it’s not the whole story. The number of teeth on any given size ratchet does not indicate its maximum torque capacity. Instead, that factor comes from the gear ratio and how many revolutions you can achieve for one complete handle turn.
Tools with a gear-tooth mechanism (such as many cordless ratchets) have a gear ratio. It means they provide more mechanical advantage when pulling than pushing; in other words, it takes fewer turns of the handle to release or fix a fastener.
The more teeth on the gear, the higher its gear ratio. For example, two 16-tooth gears have a 5:1 gear ratio (one complete turn of one gear results in five complete turns of the other). If you’re attempting to tighten a large bolt, you might choose this type of ratchet to prevent overtightening.
How many teeth are generally on a cordless ratchet?
Most cordless ratchets manufactured in the past decade feature four or two teeth for models that allow reverse rotation.
Cordless ratchets manufactured after 2010 use 6-tooth designs to provide higher torque for the same size or lighter weight, resulting in higher efficiency. The reason to use a smaller number of more significant teeth is that the higher torque (turning force) requires a larger contact area to transmit the load onto the teeth. Having smaller large teeth means that they can be oversized in diameter and therefore more vital.
During 2005 and earlier, craftsman cordless ratchets used an 8-tooth design with high torque ratings. Therefore, it was necessary to provide enough contacts to ground the load on each bit of rotation.
Also, in the 8-tooth design, there is a “dead spot” in the center where two teeth are simultaneously in contact with the bit shank, which causes chatter when used at low speed or with heavy loads.
How to choose a cordless ratchet?
The most important factors for choosing a cordless ratchet are tightening capacity, RPM of the impact mechanism, torque, and battery voltage. Different manufacturers have chosen different approaches when designing technologies for transmitting torque to an output shaft. The simplest solution is a direct drive system in which the motor itself turns the output shaft.
Another option is a gearbox that turns the output shaft with the help of gears. The third option is an electronic control system that sends impulses to speed up or slow down the motor, thus creating more torque on demand.
Direct drive cordless ratchets are simple in design and easy to use – switch them on, and you can start doing your job. The problem is that they often lack power. The RPM of the motor and output shaft match, so there’s no way to get more torque except for buying a more powerful battery pack. Even if you buy another battery, it will probably be of the same voltage and increase torque.
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