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Your Guide to Splitting Stone Using Wedges and Shims
Wedge and shims
21st Sep 2023

The history of stone splitting is as old as human culture itself, dating back to when our ancestors first discovered that they could shape and form rocks. This rudimentary knowledge paved the way for the development of more sophisticated and precise techniques, which include the use of wedges and shims

These humble tools, despite their simplistic design, enabled craftsmen to split even the hardest of stones with precision and finesse. Today, the use of wedges and shims remains one of the most effective ways to split stone.

Wedges and shims, often used in tandem, are fundamental to the process of stone splitting. The wedge, a prism-shaped tool, is driven into a pre-drilled hole in the stone, inducing a splitting force. The shims, on the other hand, are thin, flat pieces of metal that are inserted into the split to prevent it from closing. The combined action of these tools allows for controlled, precise splits, giving the craftsman greater control over the final shape and form of the stone.

However, stone type, shape, size, and other conditions can have a significant influence on how any particular stone may split. Whether you are trying to persuade a stone to split into a particular size and shape or simply reducing the size of a boulder to make it easier to move, we have outlined some basic steps and recommendations to help you achieve the best results.

Defining Wedges and Shims


Wedges are typically made from hardened steel. They are designed to fit snugly into drilled holes in the stone and exert outward pressure when hammered, causing the stone to crack along the line of the holes. The primary function of a wedge is to create a force that drives the stone apart. They come in various sizes to accommodate different stone sizes and types. The size of the wedge you choose will directly impact the precision and quality of your split, so it’s worth investing time in understanding the best fit for your stone.


On the other hand, shims, often made from the same material as wedges, are smaller accessories that work together with wedges. Shims are thin, flat pieces that are placed in the drilled holes alongside the wedges. They act as a buffer, protecting the stone from the direct force of the wedge and distributing the stress evenly across the hole. This helps to prevent the stone from shattering and enables a cleaner, more controlled split.

While both wedges and shims are sturdy and durable, they aren’t indestructible. Always inspect your tools before use for any signs of wear or damage. A damaged or worn-out tool can not only affect the quality of your split but also pose safety risks. 

No stranger to quality, Diamach is a leading supplier of stonemasonry tools in Sydney. Diamach’s premium selection of wedges and shims feature superior casting quality for a longer lifespan compared to other brands. 

Getting Started

Before using these stonemasonry tools, there are a few things to consider. This includes the type of stone you’re working with, the size and drill bit selection as well as the quantities. It’s not a one-size-fits-all situation, and understanding these nuances will be crucial in your stone-splitting project. 

Size Selection

First things first, measure the height or thickness of the stone. The size of the stone you choose to work with has a significant impact on the rest of the process. Larger stones require more effort, more equipment, and greater precision. On the other hand, working with smaller stones can be less intimidating for beginners, allowing for practice and skill development.

Wedges and shims can generally split stone up to 4-6 times the length of the wedge. For example, the wedge of our ¾in wedge and shims is 4in long, so it is reasonable to assume it can split a stone that is between 16-24in thick/high. 

Drill Bit Selection

Next, the choice of your drill bit. The size and type of the drill bit directly influence the size and shape of the hole you’ll drill into the stone. Smaller drill bits are ideal for softer stones or more intricate work, while larger bits are necessary for harder stones or larger projects.

The drill bit’s diameter should match the size of your wedges and shims. The ‘size’ of the wedges and shims signifies the hole diameter. So, ¾in wedges and shims require a ¾in diameter hole. Always make sure the drill bit can drill deeper than the length of the wedge.


The quantity of wedges and shims required is another important factor to consider. This depends on the size of the stone and the area you aim to split. A general rule of thumb is to use one shim and wedge for every inch of stone thickness. However, this can vary based on the stone’s hardness and the precision of the split needed.

Wedges and shims generally need to be placed every 4-6in along the ‘top’ of the split plane. If splitting a rounded boulder, holes would be drilled every 4-6in in an ‘arch’ across the top of the stone. Placing wedges and shims down the sides of the stone can help promote a straighter split through the stone.

Preparing the Stone

When it comes to stone splitting, it’s important to pay attention to details. The preparation of the stone is a critical step that sets the stage for the entire splitting process. It’s not just about selecting the right stone and marking where you want to split; it’s about understanding the stone’s inherent characteristics and working with them, not against them.

Stone Location

Firstly, consider where the stone is in your workspace and its position in relation to others. Next, take note of the natural grain of the stone; if you’re splitting a larger rock, are there visible fissures or lines of weakness that could guide your placement of shims and wedges? Pay attention to the stone’s surroundings too. Are there any obstacles that could hinder the splitting process? If so, you might need to reconsider your stone’s location or even the orientation of your split.

If possible, position the stone (or choose a split plane) that will allow an isolated portion of stone to fall away from your split. For example, place the stone on a piece of lumber to create a fulcrum on the bottom side of the split plane.

Layout Holes

Next, let’s talk about layout holes. These are the spots where you’ll drill into the stone to insert your wedges and shims. This isn’t a random process; successful stone splitting requires careful planning. You’ll want to consider the size and shape of the stone, the direction you want to split, and any potential obstacles. A common rule of thumb is to space the holes evenly, typically about 4 to 6 inches apart for larger stones. However, the exact spacing will depend on the specific characteristics of your stone and the tools you have at hand.

Use a straight edge to mark hole locations very 4-6in on-centre across the top and sides of the stone (if necessary). This will establish your intended split plane. Keep the first and last holes about 4-6in away from the outside edges of the stone.

Drilling Holes

Finally, the drilling process. The size of the drill bit you use should correspond with the size of your wedges and shims. Too big, and your tools might not fit snugly, resulting in an uneven split. Too small, and you risk damaging the tools or the stone itself. Always make sure the drill bit is sharp and in good condition before you begin.

At Diamach, the stonemason tool experts in Melbourne, we recommend holding the drill upright and steady during drilling to ensure each hole is plumb or drilled along the same split plane. Drill holes at least 1/4in deeper than the length of the wedge. For best practice, remember to clear the holes of any excess stone dust.

Making the Split

Now for the main event: making the split! Wedges and shims work together to exert pressure on the stone, causing it to crack along the line of the drilled holes. The wedge, a pointed piece of metal, is placed in the hole first. Shims, which are flat and rectangular, are then inserted on either side of the wedge.

Wedge & Shims Placement

The positioning of these tools determines the direction and depth of the split, making their placement a critical aspect of the process. When placing your wedge and shims, it’s essential to consider the size and shape of the stone. For long, thin stones, the wedge should be positioned at the centre of the stone’s length. In contrast, for more substantial stones, the wedge should be placed closer to one edge. This positioning allows for a more controlled split and reduces the risk of shattering or uneven breaks.

When properly positioned, about 2/3rds of the wedge should protrude above the hole from between the two shims. It is helpful to pre-assemble the wedges and shims in this position before placing them in the hole. Make sure the shims are positioned perpendicular to the split line.


With the wedge and shims correctly placed, it’s time to move on to the hammering process. A common question many novice stone splitters have is, “How hard should I hit the wedge?” The answer, as with many aspects of stone splitting, depends on the specifics of your stone and tools. However, a good rule of thumb is to start with gentle taps and gradually increase the force of your blows. This method allows the pressure to build slowly, resulting in a cleaner, more controlled split.

Use a light hammer to start tapping the wedges in sequence, firmly but without forcing, to build gradual, even pressure along the entire line of wedges and shims. Aggressive or forceful hammering will cause unnecessary damage and wear to the wedges and shims. If the wedges become too firm before a crack develops, allow the wedges and shims to briefly ‘rest’ before continuing to drive the wedges into the stone.

Diamach carries an impressive selection of metal wedges and shims in a wide range of sizes, including 12mm and 24mm. Browse our online store or reach out to us for advice on stone splitting and stone masonry tools in Sydney

Overcoming Obstacles in Stone Splitting

Even the most seasoned stonemasons occasionally encounter problems when splitting stones using wedges and shims. While stone splitting with wedges and shims can present challenges, these can be effectively addressed with adequate preparation, correct tool usage, and observing safety measures.

After all, problems are part of the learning curve, and with each stone split, you’ll gain valuable experience and skill. Let’s take a look at the most common issues you might face during the stone-splitting process with practical solutions.

One frequently encountered issue is the wedge or shim slipping out during the splitting process. This often occurs when the hole isn’t drilled deep enough or when the wedge and shim aren’t properly inserted. To prevent this, make sure you’re using a drill bit of the appropriate size for your stone. Also, make sure to insert the wedge and shim as far as they can go into the hole before beginning the splitting process.

Another common problem is a stone that splits unevenly or not where intended. This can happen due to a variety of reasons, such as varying hardness in the stone, improper placement of wedges and shims, or uneven hammering. To mitigate this, double-check that your wedges and shims are evenly spaced and that you apply consistent force when hammering. In some cases, you might need to adjust your technique based on the specific characteristics of the stone. For instance, softer stones or stones with existing fault lines may require a gentler approach.

Additionally, you might face challenges when trying to achieve precise splits, particularly in instances where the hole diameter is limited. In such cases, it is essential to use smaller wedges and shims and to proceed cautiously. Ensure that your holes are drilled straight and evenly spaced to maintain control over the direction of the split.

Expert Tips for Challenging Splits

    • For soft stone or difficult splits, consider drilling holes closer together and/or deeper into the stone to help weaken the stone along the split plane. This may also help increase the splitting capacity of the wedges and shims when faced with a difficult or precise split, or when circumstances limit the hole diameter that can be drilled.
    • When splitting stones that are partially buried or splitting off sections of ledge/bedrock, expose as much of the stone as possible and focus on splitting off fully exposed sections of stone.
    • The type of stone you’re working with will influence your preparation process. Softer stones may require more delicate handling, while harder stones may need more forceful drilling. Always consider the unique characteristics of the stone before starting any preparation.
    • Remember safety should always be a priority. Double check you have the right personal protective equipment (PPE), follow all precautions and never rush the process. Patience and attention to detail are key to successful stone splitting.

    Not all Wedges and Shims are Created Equal

    The effectiveness of wedges and shims is largely contingent upon their quality and the skill with which they’re used. High-quality tools can withstand the force required for stone splitting and ensure a successful split, while low-quality tools may fail under pressure, leading to an unsuccessful attempt at splitting the stone. This reinforces the importance of investing in good-quality tools and honing your skills through practice.

    Diamach‘s premium range of wedges and shims feature great quality casting for longer life when compared to other brands. With over 25 years of experience supplying stonemasonry tools in Sydney, you can trust the team at Diamach to stock only the highest-quality products for purchase. 

    Choose High-Quality Stone Mason Tools in Sydney

    A craftsman is only as good as his tools, which is why Diamach’s range of wedges and shims is designed to last. To find out more about our modern and innovative range of stone mason tools in Sydney, browse our online store here.

    As always, if you need product advice or technical help, send us a message or call (02) 8915 5095.

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