The thumb and grab make it relatively easy for the excavator to pick, place and sort materials for removal. But choosing the right tool for your job is complicated by the wide selection. There are many different types and configurations of thumb and grapple, each with unique advantages and limitations.

Make the right choices and you will be rewarded with increased productivity. With the wrong attachment, productivity will be affected and/or the uptime and overall service life of the attachment will be reduced.

Bucket Thumb Considerations

The bucket/thumb combination can handle most tasks and provides an efficient solution if you need to dig with your machine. The thumb of the excavator bucket, just like the thumb on your hand, can grab oddly shaped objects and then fold them up for normal digging and loading.

However, this is not a one-size-fits-all solution. There are many types of thumb shapes on the market today. Most thumbs are designed to handle just about anything, but certain types of thumbs can be more efficient.

For example, if the fragments are smaller in nature, a thumb with four more closely spaced spikes is much better than one with two more widely spaced spikes. The larger debris reduces tines and provides greater spacing, providing better visibility for the operator. The thumb will also be lighter, which gives the machine a bigger payload.

Hydraulic and mechanical versions are also available with various teeth, meshing with bucket teeth. The mechanical thumb is usually mounted on a simple welded support and does not require special pins or hydraulics. They provide a low-cost solution for occasional use, while hydraulic thumbs provide a strong, positive grip.

The flexibility and precision of the hydraulic thumb will prove to be more effective over time, allowing the operator to grab objects more easily.”

However, there is a trade-off between cost and productivity. Hydraulic thumbs are more expensive, but they will be superior to mechanical models, and most purchases are related to the work of the thumb. If you use it every day, I suggest you use hydraulic. Mechanical use may make more sense if used only occasionally.

The mechanical thumb is fixed in a position against which the bucket must be bent. Most mechanical thumbs have three manually adjusted positions. The hydraulic thumb has a wider range of motion, allowing the operator to control it from the cab.

Some manufacturers also offer progressive linked hydraulic thumbs that provide a greater range of motion, typically up to 180°. This allows the thumb to grasp the entire range of the bucket. You can pick and place objects near the end of the stick. It also provides load control through most of the bucket’s range of motion. By contrast, the connecting rod free hydraulic thumb is simpler, lightweight, and typically has a range of motion from 120° to 130°.

Thumb installation also affects performance. The universal thumb, or pad thumb, has its own main needle. The bottom plate is welded together with the stick. The pin thumb uses a barrel pin. It requires a small bracket welded to the stick. The hydraulic pin thumb maintains its relationship to the bucket rotation and is designed to match the radius and width of the bucket tip.

The thumb hinged with the barrel pin allows the thumb and barrel to rotate in the same plane, and when placed on a plate mounted on a stick, the relative length of the thumb tends to shorten to the radius of the barrel tip. Pin thumbs are usually more expensive. Welded thumbs are more versatile in nature and are designed to fit their respective excavator weight classes.

The pin thumb has several advantages over the stick thumb. With the pin mounted on the thumb, the tip is crossed with the tooth regardless of the position of the bucket (fully crimp into a partial dump). When the bucket is removed, the thumb is also removed, meaning the thumb is not sticking out under the arm, which could damage or get in the way. No pivot bracket on the rod interferes with other attachments.

The pin thumb is also suitable for pin clips and quick connectors. The thumb is separated from the bucket and left on the machine. But because there was no quick connector, the kingpin and thumb had to be removed along with the barrel, which meant extra work.

Thumb mounted on a stick also has several advantages. The thumb remains on the machine, unaffected by attachment changes and easily removed (except for the base plate and pivot) when not needed. But the tip of the finger only intersects the barrel tooth at one point, so the length of the thumb is important. When using a pin clamp, the thumb needs to be extra long, which increases the torsional force of the bracket.

When choosing the thumb, it is important to match the tip radius and tooth spacing. Width is also a consideration.

Wide thumb is suitable for picking up municipal garbage, brushes and other bulky things. However, a wider thumb creates more twisting force on the brace, while more teeth equals less gripping force per tooth.

A wider thumb will provide more material, especially if the bucket is also wide, and in addition, fragment size can be a factor in the loading protocol. If the bucket is mainly loaded, the thumb plays a supporting role. If the machine is using the bucket in neutral or extended position, the thumb now carries more load, so width becomes a more important factor.

Demolition/Sorting Grapples

In most applications (demolition, rock handling, waste disposal, land clearing, etc.) grapple are usually more productive than thumbs and buckets. This is a must for disassembly and serious material handling.

Productivity will be better applied with a grab where you are processing the same material over and over again, without the need to dig with a machine. It has the ability to grab more material in one pass than a bucket/thumb combination.

The grab is also more effective on irregular objects. Some items are easy to lift, but hard to place between bucket and thumb.

The simplest configuration is the contractor’s grapple, which features a fixed claw and an upper jaw that operates the barrel cylinder. This type of grapple tends to cost less and have less maintenance.

Disassembly and sorting grab can greatly improve the productivity of primary or secondary disassembly applications. They are able to move large amounts of material when sorting recyclables.

In most cases, demolition combat is ideal, and removing the grab provides great versatility, giving the operator the ability not only to pick up debris, but also to create it. A lighter grab can be used, but it is generally not recommended for disassembly. Similar to the thumb, a lighter duty, wider grip may be better suited to your needs if the removal is done in a different way.

You can use different types of crawls for each application to optimize sorting and loading. Sorting requires input from the customer to decide what to pick and let go to waste. This grab type allows the operator to rake material, as well as pick and load.

Depending on whether the material and grab are used for any demolition, it may be decided what is used for loading. Most contractors use what’s on the machine to do everything. If you have the opportunity, try to do both. Removing the grab handles the heavy work, allowing lighter/wider grabs to handle smaller material.

Durability is of Paramount importance when dealing with disassembly debris. Most sorting grabs have internal cylinders and rotary motors, which require two additional hydraulic loops. They are not as robust as mechanical disassembly, and most loading is done with mechanical grabs that operators can crush without damaging.

The mechanical demolition fight is simple, with few moving parts. Maintenance costs are kept to a minimum and wear parts are limited to wear caused by loading and unloading materials. A good operator can spin, flip, manipulate and sort materials quickly and efficiently with a mechanical grab without the expense and headache of spinning the grab.

If the application requires precise material handling, however, a rotary grab may be a better choice.It provides 360° rotation, which allows the operator to grab the machine from any Angle without moving it.

The performance of rotary grapple is better than any fixed grapple under suitable operating conditions. The disadvantage is hydraulics and rotators, the price will go up. Weigh the initial costs against the expected benefits and be sure to check the rotator design to ensure it is completely free from debris.

Tooth spacing is an important factor to consider in material sorting. Ideally, unwanted materials should easily pass through the grab, which creates faster and more efficient cycle times.

There are many different time configurations available. In general, if the client is dealing with smaller pieces, more fangs should be used. Demolition fights usually have a 2-3 time configuration to pick larger items. A grab for brushes or sundries is usually a three-to-four design. The larger the contact area of the grab bucket to the load, the smaller the clamping force.

The type of material handled will have a significant impact on the most appropriate time configuration. Heavy steel beams and blocks require more than twice as much configuration, and general purpose removal takes three times as long to configure. Brushes, municipal waste and bulky materials require four to five tips. Precision pickup requires an optional hydraulic support instead of the standard rigid support.

Depending on the material you’re working with, ask for advice on time intervals. Bonovo provides a solution for all types of materials, and we have the ability to create custom time intervals that allow pieces of a specific size to fall while retaining what is needed. These tooth spacing can also be plated off to retain as much as possible.

Plate and ribbed shell designs are also available. Plate shells are more used in the waste treatment industry, while ribbed shells tend to trap materials in the ribbed shells. The plate shell is kept clean and keeps working longer. On the ribbed version, however, the depth of the ribs gives the shell power. Rib design can also increase visibility and material screening.

Quick Couplers Impact Choice

Some disassembly grabs can be used with or without fast couplers. (The direct PIN-on grab usually does not work well on couplers.) If you plan to use quick fasteners later, it’s best to buy them with the grab, which needs to be installed in the factory to work with the fastener. Refurbishing the grab at a later date is quite expensive.

Quick grabs mounted on couplers are a compromise, and they may tend to be ‘two-pronged’, making it more challenging for the operator to master. Due to the center of the needle and the extra height, the force is lower. Direct nailing in the grab provides the simplest and most efficient mounting option. There is no double action, the breaking force of the machine increases by increasing the pin center distance.

Specially designed fastener mounting grab is available. Bonovo provides a grapple that hangs on the coupler and maintains the same geometry as the PIN version. The two halves of this grapple are connected by two short pins, which are machine rod pins held in a straight line. This provides proper rotation without sacrificing the use of the coupler.

Thumb Selection Considerations

Provides the following criteria to consider when choosing a thumb:

• Thickness and types of steel used in manufacture (QT100 and AR400)
• Replaceable tips that fit between the bucket teeth
• Replaceable bushings
• Hardened alloy pins
• Intersecting tips for picking of fine material
• Custom thumb profile and tooth spacing built specifically to suit the application
• Cylinder pressure rating and bore stroke
• Cylinder geometry that provides a good range of motion yet strong leverage
• Cylinder that can be flipped to change port positions
• Mechanical lock for parking the thumb when not in use for extended periods
• Easy to grease when parked

Grapple Selection Considerations

Provides the following criteria to consider when choosing grapple:

• Thickness and types of steel used in manufacture
• Replaceable tips
• Replaceable bushings
• Intersecting tips for picking of fine material
• Hardened alloy pins
• Strong box section design
• Continuous stringers that run from the tips to the bridge
• Heavy-duty brace and brace pins
• Heavy-duty stick bracket with three positions and an internal stopper to assist installation.