A mini excavator thumb is a tool that is mounted on the end of the stick of an excavator, and rotates opposite the rotation of the bucket. Having a thumb on an excavator allows it to tackle a larger variety of tasks by making the machine capable of picking up larger rocks, logs, stumps, brush, construction debri, or even other tools such as a rake or a grade beam. Excavator thumbs or clamps come in several different styles.
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The most basic design is a manual thumb that welds directly onto the face of the stick, above the bucket. This thumb is operated manually into fixed positions either by the operator getting off of the machine or by a helper on the ground. The next step up from the mechanical thumb is a stick mounted hydraulic thumb. These thumbs are a little more expensive and can be operated from the cab.
You should be aware when thinking about buying a stick mounted mini excavator thumb of any kind that most suffer from poor range of motion as well as they cannot maintain the proper distance to your bucket throughout that rotation. These thumbs do function ok but generally their design is such that they get mass produced with “a one size fits lots of different machines” mentality and the result is they work ok on lots of machines but not really good on any of them. Next up is the pin mounted hydraulic excavator thumb. These thumbs mount on the same pin as the bucket hinges on.
The installation of these thumbs is a bit more involved but they are superior in their performance to the stick mounted thumbs and are well worth a little extra time to install them. Because these thumbs anchor on the same pin as the bucket, the bucket and thumb rotate all the way through the range of motion together seamlessly.. This makes manipulating anything the machine is holding much easier.
The last type of mini excavator thumb is the progressive link thumb. The progressive link thumb is also a pin mounted thumb but instead of the cylinder mounting directly to the thumb , the cylinder pins to a set of linkage that affords the progressive link more power, a greater range of motion (20 to 40 degrees more than a non-link), but also moves through its range of motion faster. Progressive link thumbs are typically 15% to 25% more money than a standard non-link thumb. For most applications a well engineered non-link thumb will work for very well for most operators, without spending the extra money for the link style thumb.