South Fork Industrial developed the first hydraulic thumbs for use on Caterpillar wheel hoes equipped with E-stick. The thumb travels in and out with the bucket and can be used with the Cat mechanical quick change. We also offer a thumb for the Schaeff walking spider hoe. Click on a thumbnail below to view a larger image or click on "thumb.mpg" to see the thumb in action.

For additional information, please select one of the documents below. All documents are in Adobe Acrobat format. Click here to download the latest version of Adobe Reader.

South Fork Industrial CAT Thumb product brochure (115 KB)
420D with QC Thumb Installation Instructions (1.19 MB)
Instructions For Adding Extra Valve Section (200 KB)
Pin Grabber Thumb vs. Standard Thumb (77.5 KB)
Parts Needed From CAT To Install Extra Valve (12.7 KB)

Additionally, please see our Thumb FAQ section below.

thumb.mpg (28 Sec, 355KB)


Thumb FAQs

Who needs a thumb on a wheel hoe?
Anyone who:

  • Has rented a jackhammer to break up a concrete slab so they could load out the pieces in the front bucket.

  • Demos buildings or sorts through debris - i.e. landfills

  • Handles pipe & culvert or cleans out plugged culverts

  • Is a Landscaper

  • Is an Emergency responder

  • Are there disadvantages?
    Some. If you are an electrical contractor or do lots of underground utilities, our thumb may not be for you.
    As our thumb is 15 – 16” wide, it will be in the way if you are digging deep narrow trenches.
    It also adds 320 lbs. to the end of the stick. You will want all the counterweight you can get in the front.

    Will the thumb work with any bucket?
    Designed for and works best with 219-3387 bucket.
    Any bucket can be made to work with thumb if the teeth are arranged to nest.
    Teeth on thumb are shipped loose so they can be welded on to clear bucket teeth.
    Leg extenders are available.
    Not recommended for high capacity buckets.
    The thumb leg has to be extended so far to mate with a high capacity bucket that much of the leverage is lost. This is especially true if a high capacity bucket is used with a pin grabber quick coupler.

    Will I need to add another valve to operate the thumb?
    Probably. We find very few machines were equipped with a 6th valve from the factory.
    Many customers running a hammer or compactor think they have an extra valve when in fact they only have the lines group to Tee into the E-stick circuit and run a one way attachment like a compactor.

    If you only have one foot pedal (on the RH side when operating the backhoe), you most likely do not have the 6th valve. A machine factory equipped with a 6th valve has a pedal on the LH side. Count sections in main stack to verify.

    How hard is it to install the extra valve?
    It’s no picnic.  But nothing your CAT dealer or an experienced heavy equipment mechanic with the right tools and a good pressure washer can’t handle. We have a good set of instructions with a few shortcuts available for download.

    Can’t I just use a diverter valve?
    Please don’t. While it is possible to use a diverter, you really need to install a thumb protection valve between the diverter and the thumb. This requires an extra line back to the tank. Considering the extra cost of the protection valve, the extra plumbing required and the fact there is no really good place to install the valve, we believe adding the extra valve to the stack makes for a cleaner, more factory-like installation.

    Will I get all the parts I need to install the thumb?
    No. You will need to get two steel tubelines from CAT. These are duplicates of the steel lines that run along the top of the main boom. These make for a nicer installation than just adding a couple hoses and turkey-tying them to the existing hoses. These will run about $100 ea.

    Will I get all the hoses needed?
    Yes. You will get all the hoses needed.