Yamamoto FAQs

Choosing the right model depends mainly on three factors:

• The type of project
• The total volume of rock to be excavated
• The drilling capacity available on site

For smaller projects or limited volumes, the HRV-1000 is usually the better choice. For larger volumes—typically more than a couple of hundred cubic meters—the HRV-1700 is more suitable.

In general, the HRB-1700 delivers more than double the production rate (volume per hour) compared to the HRB-1000, making it the preferred solution for high-volume rock excavation.

However, drilling capacity is often the limiting factor.

HRB-1700 requires 5-inch diameter drill holes, which means you need a large and capable drilling rig.

HRB-1000 requires 4-inch diameter holes, which are much easier to achieve with commonly available drill rigs.

For confined projects such as small shafts or tunneling, the HRV-1000 is generally better suited. It is more compact, easier to maneuver, and can be handled by smaller excavators that fit into restricted spaces. In tunneling applications, it is also difficult to find drill jumbos capable of drilling holes larger than 102 mm.

Additionally, the HRB-1000 offers an optional 3-inch wedge set, providing even more flexibility for projects with limited drilling capacity.

Hydraulic rock splitting is often compared to several alternative methods:

Hydraulic rock breakers tend to become very inefficient when rock compressive strength exceeds 8,702-11,603 psi, especially in confined spaces without free faces to break toward. Productivity drops sharply, noise levels are high, and precision is limited.

Expanding mortar can be useful because it works with smaller hole diameters and handheld drills. However:

• It requires many closely spaced holes
• It is labor-intensive
• It is costly per cubic meter due to material consumption
• It is slow and unpredictable, often requiring 12 hours or more to see results—and sometimes the rock does not crack at all

That said, many users of Yamamoto Rock Splitter combine expanding mortar with hydraulic splitting. A common method is stitch drilling, where closely spaced holes are drilled and expanding mortar is used in perimeter holes. This helps release rock that cannot be accessed directly with the splitter and improves break-out at the final boundaries.

Wire sawing is also frequently used together with rock splitting. Wire cutting is ideal for defining precise perimeters, while rock splitting is used for efficient bulk breakage inside the cut area. Even in small openings, wire sawing can create a free face to split toward, significantly improving productivity.

The method used to create a free face depends mainly on the rock type and hardness.

If the rock is not extremely hard—typically up to around 14,500 psi, such as limestone, sandstone, or other relatively softer rock types—it is usually sufficient to create a starter pit. This is done by drilling several holes close together, splitting the rock, removing the broken material, and then re-splitting in the same area. By repeating this process, a pit is gradually formed that provides a free face to split toward.

Typical pit sizes:
HRB-1000: approx. 3 × 3 feet, about 3 feet deep
HRB-1700: approx. 6 × 6 feet, about 6 feet deep

Once this pit is established, it functions as a free face, allowing the splitting operation to expand outward efficiently.

For harder rock types (granite, basalt, etc.), it is difficult to create the initial pit by simply drilling holes in close proximity. In these cases, slot drilling is commonly used. Slot drilling involves drilling overlapping holes so there is no intact rock bridge between them. This is typically done using a guide rod on the drill rig, where the guide rod is placed into the first hole to allow the next hole to be drilled extremely close and partially overlapping.

By drilling a series of overlapping holes—usually forming a slot around 1 meter (10-13 feet) wide—you create an artificial free face. Once the slot is completed, splitting can begin toward it, and the free face can then be expanded into a larger pit.

In tunnels or other highly confined spaces, a larger slot is often required—sometimes across a significant portion of the tunnel face—to create enough free face area for effective splitting.

There is also an option of drilling diagonal holes that is using the surface as a partial free face. The angle of the holes is then increased so the initial pit gets deeper and deeper until the holes can be drilled vertically. This is quite labour intensive and time consuming, so this is usually only used in a large pit excavation where this is done once only. This method is not recommended for shaft sinking or tunneling.

Alternative methods to create a free face

Depending on site conditions and available equipment, other methods may also be used, including:

• Drilling overlapping large-diameter holes using core drills or DTH hammer drills
• Wire sawing to cut a slot or perimeter, creating a clean face to split toward

Many users of Yamamoto Rock Splitter combine these methods with hydraulic splitting to adapt to different rock conditions and space constraints.

Productivity depends on several interacting factors, so there is no single fixed output figure. In most projects, the limiting factor is not the splitter itself but the overall excavation process, especially drilling.

1. Drilling capacity (most critical factor)
Drilling usually takes significantly more time than splitting. In many projects, the splitter is waiting for drilling to be completed.

The faster and more efficiently you can drill, the higher your total production rate will be. A high-capacity drill rig is therefore essential for achieving good productivity.

2. Splitter model (HRB-1000 vs HRB-1700)
The choice of splitter has a major impact:

• HRB-1700 typically delivers more than double the capacity of HRB-1000
• Higher splitting force allows wider hole spacing
• Longer wedge length enables deeper splitting per cycle

In practice, this often results in more than twice the volume per hour compared to HRB-1000, provided the drilling capacity is available.

3. Rock hardness
Rock strength directly affects hole spacing:

• Harder rock → holes must be drilled closer together
• Softer rock → wider spacing is possible, increasing productivity

This is why the same splitter can perform very differently in different rock types.

4. Job size and working geometry
Project layout has a big influence on output:

• In a large open pit or bench, drilling, splitting, and rock removal can happen in parallel. This allows for very high production rates
• In narrow shafts or confined spaces, work often has to be done sequentially (drill → remove drill → split → muck out), which significantly reduces capacity

5. Availability of a free face
Whether a free face already exists also matters:

• In open pit excavation, a free face is maintained and productivity remains high
• In shafts or tunneling, a new free face must be created continuously as work progresses, which lowers overall output

Because productivity depends on drilling capacity, splitter model, rock type, job size, geometry, and free-face conditions, there is no single universal productivity figure.

For realistic expectations, the best approach is to contact the sales team at Yamamoto Rock Splitter, who can review your specific project conditions and provide a tailored productivity estimate.

The Yamamoto Rock Splitter is a low-maintenance machine, with very few wear parts. Most maintenance is related to consumables rather than complex servicing.

1. Special grease (primary consumable)
The most important consumable is the special wear-resistant and heat-resistant grease applied between the wedge and counter wedges.

During splitting, metal slides against metal under extremely high pressure, so a standard grease cannot be used. This dedicated grease is supplied with the splitter and should be applied regularly. Proper greasing significantly extends wedge life and overall performance.

2. Wedge set (main wear component)
The wedge and counter wedges are the main wear parts and will gradually wear over time. Their service life depends on several factors:

• Total operating hours
• Rock hardness and abrasiveness
• Frequency and quality of greasing
• Operator technique

Many customers use one wedge set for around 12 months, but this can vary. Some replace wedges after 6 months, others after 12 months or longer. It is not a frequently replaced component and is considered a normal long-term wear item.

3. Minor wear parts
There are a few small components associated with the wedge mounting that wear gradually. For example: Rubber washers that help keep the counter wedges pushed towards the centre wedge.

These are simple, inexpensive parts and are typically replaced every 6 months, depending on usage.

4. Hydraulic cylinder seal kit
The splitter cylinder includes a seal kit. The general recommendation is to replace the seals every two years, although many customers operate the splitter for several years without needing a seal replacement. This is not a high-maintenance item.

Overall, apart from regular greasing and periodic inspection of the wedges, the Yamamoto Rock Splitter requires very little routine maintenance. This simplicity is one of the reasons many contractors choose Yamamoto Rock Splitter for long-term, demanding rock excavation projects.

The mounting method depends mainly on how the splitter is used—vertical or horizontal—and on the type of project.

Vertical splitting (most common applications)

For the majority of users—such as in open pit excavation, trenching, and building foundations—the most efficient setup is to hang the splitter freely from the excavator using a wire or chain, while powering it with the excavator’s hydraulics.

This method offers several important advantages:

• The splitter slides into the drill hole by its own weight, instead of being forced in
• Reduced friction during insertion
• Significantly lower risk of damaging or breaking the wedges
• During splitting, the tool can move naturally inside the hole, further reducing stress on the wedge set

Free-hanging vertical operation has proven to be a very efficient and reliable way to use the splitter in production work.

Horizontal splitting (tunneling)

In tunneling or shaft work, the splitter is often used horizontally. In these cases, the splitter is mounted fixed to the excavator boom.

To avoid excessive stress during insertion, a standard rigid mounting is usually not sufficient. For this reason, Yamamoto Rock Splitter offers a special mounting solution that includes:

• A telescopic boom
• Rotation
• Side-swing bracket
• Limited free movement up/down and left/right

This controlled flexibility allows the splitter to align naturally with the drill hole, making insertion smoother and significantly reducing the risk of wedge damage.

Hole spacing depends on three main factors:

1. Splitter model
2. Rock hardness
3. Type of project and confinement

There is no single universal spacing, but the following guidelines are commonly used as a starting point.

1. Splitter model
In hard rock such as granite, typical starting values are:
HRB-1000: 1.5 × 1.5 ft (center-to-center)
HRB-1700: 2.5 × 2.5 mm (center-to-center)
The HRB-1700 has higher splitting force and a longer wedge, allowing wider spacing and deeper splitting per cycle.

2. Rock hardness
In softer rock, such as limestone, spacing can often be increased significantly:
HRB-1000: up to 2.5 × 2.5 feet
HRB-1700: up to 3.5 × 3.5 feet
As rock hardness increases, holes must be drilled closer together. Hard, massive, or unfractured rock requires tighter spacing.

3. Project type and confinement
Geometry plays a major role:

• In trenches or small shafts, the rock is more confined and harder to release, so spacing often needs to be reduced
• In open pit or bench excavation, wider spacing is usually possible

Another factor is how the rock will be removed after splitting:

• With tight spacing, split rock is often fully released and can be removed using a bucket or ripper
• With wider spacing, the rock may crack but remain partially locked, requiring a rock breaker to knock it loose after splitting

Site-specific testing is essential
While there are benchmark values and proven experience, optimal hole spacing must usually be tested on site. It depends on:

• Drill accuracy
• Available breakout tools
• Operator technique
• Local rock conditions

Spacing may even vary within the same project. For example:

• Near the surface, rock is often weathered or naturally fractured, allowing wider spacing
• Deeper layers are typically more solid and require closer hole spacing

For this reason, most projects start with conservative spacing and then adjust based on actual performance, with guidance from the team at Yamamoto Rock Splitter.

The short answer is: it depends on site conditions and workflow. Both methods are used in practice, and each has advantages and challenges.

Understanding splitter working depth

To split rock, the drill hole must always be deeper than the effective splitting depth. For example:

• With HRB-1000, a typical hole depth is 5 ft
• The effective splitting depth is about 3 ft

This means roughly 33% of each drilled hole is not used in a single splitting cycle.

Drilling full depth and splitting in multiple cycles

From a drilling-efficiency standpoint, it is often more efficient to drill the full depth of the excavation from the start and then split the rock in several cycles using the same holes. This approach:

• Maximizes the use of each drilled hole
• Reduces repeated drilling
• Works best when a high-capacity drill rig is available

Typically, holes are drilled to full excavation depth, plus a small extra allowance so the center wedge tip can fully engage at the bottom.

The Main challenge with drilling full depth is that, as excavation progresses, the holes tend to fill with gravel, crushed rock, and sand, making it difficult to reuse them for the next splitting cycle.

Common methods to keep holes reusable
Contractors use several practical solutions to manage this:

1. Filling holes after drilling

• Sand
• Clay balls
• Foam tubes

These materials prevent debris from entering the hole and make it easier to locate and clean later.

Out of the above options, the clay (LECA) balls seem to be the most efficient due to:

• They are easy to see as the colour differ from the rock
• They flush out easily with compressed air
• They do not compact like sand

2. Re-drilling with a smaller bit

For example, with HRB-1000:

• Split hole: 4 in
• Clean-out drill: 3 in

The smaller drill bit is used to break loose lodged material and flush the hole clean with compressed air.

Layer-by-layer drilling and splitting

In more confined sites, or where hole management is difficult, some operators choose to:

• Drill
• Split
• Remove rock

…and then repeat the process layer by layer

This is simpler operationally but less efficient in terms of drilling utilization, since part of every hole is effectively lost in each cycle.

What’s the best approach?

There is no universal rule. The decision depends on:

• Drill rig capacity
• Excavation depth
• Rock type
• Hole-cleaning practicality
• Site logistics and operator experience

For this reason, many projects use a hybrid approach, adjusting the method as excavation progresses. The team at Yamamoto Rock Splitter typically advises customers based on actual site conditions rather than fixed rules.

Yes — within limits, both smaller and larger excavators can be used, but there are important practical trade-offs to consider.

Using a smaller excavator than recommended

In many cases, a smaller excavator still has sufficient hydraulic power to operate the splitter at full hydraulic capacity. However, there are two main limitations:

1. The splitter is long and suspended from the excavator, typically hanging from a wire. When moving the splitter between holes, it is often held high in the air. This can make the excavator unstable or “dippy”, especially on uneven ground.
2. Smaller excavators have a shorter arm reach. You may need to track the excavator frequently from hole to hole. This reduces productivity compared to positioning the splitter using the arm alone.

So while a smaller excavator can power the splitter, site handling and efficiency often suffer.

Using a larger excavator than recommended

Using a larger excavator is not a problem for the splitter:

• The splitter operates on fixed hydraulic settings
• There is no risk of damaging the splitter, as it hangs freely and operates within specified hydraulic limits

However, you do not get more splitting power by using a larger machine

The main downside is higher fuel (diesel) consumption, since the excavator is larger than necessary.

Some users prefer a larger excavator, despite higher fuel consumption, as there are practical advantages:

• Greater reach, allowing you to cover a larger working area without moving the machine
• Many times the same excavator is used for splitter, breaker and bucket so with a larger excavator you can use a more powerful breaker and a larger bucket

For this reason, some users intentionally choose a larger excavator, not to increase splitting power, but to improve handling, cleanup, and loading performance.

In summary, excavator size affects handling, reach, stability, and overall site productivity, but not the splitting power itself. The best choice depends on the balance between fuel efficiency, machine stability, and how much material handling is required after splitting.

For project-specific guidance, the team at Yamamoto Rock Splitter can help match excavator size to your exact operating conditions.

Yes, a Yamamoto Rock Splitter can be used with a crane, but it requires a separate hydraulic power pack. Crane hydraulics are normally not suitable for rock splitting, so an external power source is needed. And due to the hydraulic requirements of the splitter, the power pack must be relatively large and high-capacity.

The splitter is suspended from the crane and connected to the hydraulic power pack via hoses. This setup works well in applications where excavator access is limited such as smaller shafts.

It is strongly recommended to use a radio-controlled power pack. This allows the operator handling the splitter also control the wedge movement.

In short, crane operation is entirely possible, provided a suitably sized hydraulic power pack is used. Many users choose this setup for special applications where excavators are impractical, with guidance from Yamamoto Rock Splitter to ensure the correct power pack configuration.

In short, there is no upper limit on rock hardness for hydraulic rock splitting. So far, there is no known rock type that cannot be split using a Yamamoto Rock Splitter. Even very hard granite, basalt, and volcanic tuff have been successfully split in real projects.

Rock hardness is handled by adjusting the drilling pattern:

• Harder rock → closer hole spacing
• Softer rock → wider hole spacing

By reducing the distance between holes, sufficient tensile stress is generated inside the rock to initiate controlled splitting—even in extremely hard, massive formations.

For rock-specific guidance and recommended drilling patterns, the team at Yamamoto Rock Splitter can advise based on your actual geology and project setup.

Yes — the Yamamoto Rock Splitter can be used underwater without any problem. Submerged operation does not affect the splitter itself or its splitting performance.

The challenges are operational, not technical. The following factors make underwater use more difficult:

• You must first drill relatively large-diameter holes underwater, which requires suitable drilling equipment
• A diver is typically needed to guide and position the splitter accurately into the hole
• After splitting, you need a method to remove the broken rock, such as lifting, dredging, or grab equipment

These factors make underwater splitting more complex and slower compared to dry conditions, but they do not limit the splitter’s functionality.

In summary, underwater splitting is entirely feasible from a technical standpoint. Success depends mainly on drilling capability, diver support, and material removal logistics, rather than on the splitter itself.

Yes. As a general rule, training and commissioning are always included when a Yamamoto Rock Splitter is supplied.

We normally visit the job site to:

• Commission the splitter properly
• Train operators in correct operation
• Train maintenance staff in daily and periodic maintenance

This ensures the splitter is used safely, efficiently, and at full potential from day one.

Correct operation and maintenance are critical for:

• Achieving maximum productivity
• Extending wedge life
• Avoiding common mistakes that can lead to unnecessary wear or downtime

Most issues seen in the field are not technical failures, but rather the result of incomplete understanding of operating principles. Proper training eliminates these risks.

In some markets, training is delivered directly by Yamamoto Rock Splitter personnel. In other markets, it is handled by trained local dealers, following Yamamoto’s commissioning and training procedures

In short, commissioning, operator training, and maintenance guidance are considered essential parts of the delivery, ensuring customers get the best performance and longest service life from their splitter.

The operation of the splitter itself is quite simple. Once hydraulic flow and pressure are set correctly, there is very little that can go wrong with the splitter.

Most early issues are not related to the splitter, but to the drilling.

The most common mistakes are:

1. Incorrect hole diameter

Each splitter model requires a specific hole diameter.

If the hole is too small or too large, the splitter will not work optimally or may not fit correctly.

2. Incorrect hole spacing

Hole spacing must be adapted to:

• Rock hardness
• Rock type
• Project geometry (open pit, trench, shaft, tunnel)

If spacing is too wide for the rock conditions, the rock will not split effectively. If spacing is unnecessarily tight, productivity drops.

Curved or poorly drilled holes

Holes must be straight.

If holes are curved or “banana-shaped”:

• The splitter cannot be inserted to full depth
• The hole becomes unusable
• Splitting depth and efficiency are reduced

Insufficient hole depth

Sometimes holes are drilled to the correct depth initially, but:

• Gravel, sand, or crushed rock falls into the hole
• The effective depth becomes too shallow

If the hole is not deep enough, the splitter cannot engage properly and splitting performance suffers.

Incorrect hole angle

Hole orientation is critical. Holes should be vertical or angled toward the free face.

If holes are angled away from the free face, the spacing at the bottom of the hole becomes much larger than intended. This means too much rock has to be displaced sideways, and the splitter will not work efficiently.

Summary

Most startup problems come down to:

• Drill accuracy
• Hole geometry
• Hole cleanliness
• Correct spacing for the rock conditions

This is why proper commissioning and training—provided by Yamamoto Rock Splitter or its authorized dealers—focus heavily on drilling practices, not just splitter operation.