Which Gear Hub Style is Best for Your Application?
Spur gears, sometimes called straight-cut gears, are the simplest and most popular style of gear. They are cylindrical, with teeth on the outside, parallel to the axis. They are offered with several hub styles. Often, we are asked to explain the difference, and help choose which would be ideal for a particular application. Here’s the high level overview:
With a pin style, the hub has a tapped hole with a set screw and a sub-drill that allows pinning to the shaft. Pinning is achieved by starting with the set screw, which is tightened in a specific position on the shaft. At 90° to the set screw, there is a drill spot or dimple that allows drilling through the hub and shaft. Then a dowel pin is driven into the hole. Once the pin is placed, the set screw is removed and discarded. Otherwise, it could get loose and cause preventable damage. No need for that! A pin style hub should be used where a more permanent installation is required.
With a split hub configuration, the hub is slotted, and uses a clamp for attachment to the shaft. The thin walled hub protrudes from the face of the gear. The clamp then goes over the hub and compresses it, holding it into position on the shaft. This allows the user flexibility as the gear can be repositioned. It also is used in situations where you cannot drill into a hardened shaft.
As the name implies - there is no hub in this scenario. Instead, gears have a standard precision bore for press-fit to a hub or cluster gear. There are a couple of benefits to this method. First, the staking keeps the gear from rotating relative to the hub. It also prevents the gear from working off the end of the hub. Hubless methods use less material, and are therefore lighter. They are also more compact.
In some applications, there are just gears without a set screw or clamp type hub - just a gear. Here, the gear is heated until it expands, then put onto a shaft. It shrinks as it cools, forming a permanent bond. This approach is typically used for heavy duty applications, and does not allow for interchangeability. Also, note that some manufacturers offer different versions of the clamp style hub, such as an integral clamp.
So, which is best for you? Well, it depends. For applications requiring a more permanent installation - consider a pin hub. If you require more control and plan on repositioning the gear, then a split hub is your best option. If you require a lighter, more compact approach - then hubless is likely the right choice. When in doubt, consult an application engineer that works for your supplier - chances are, they’ve solved your problem before and are willing to help.
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