Mortar Rake Bit vs Diamond Cutting Disc: Which Is Better for Removing Mortar?
Old mortar can become loose, cracked, or weathered after years of exposure to rain, frost, and temperature changes. When the joints begin to fail, removing the damaged mortar is the first step towards repointing the brickwork. The job sounds straightforward, but choosing the wrong tool can turn a simple repair into a much bigger task, particularly when the joints are narrow or the bricks are already showing signs of wear.
Two common options are a mortar rake bit and a diamond cutting disc fitted to an angle grinder. Both can remove mortar, but they approach the job differently. A mortar rake bit is made for working along masonry joints, while a diamond cutting disc is primarily designed to cut through materials such as brick, concrete, and stone.
For most repointing jobs, I would look at a dedicated mortar rake bit first, especially when the aim is to clear out old mortar without unnecessarily widening the joints. A diamond cutting disc still has its place, particularly when straight cuts are needed. The important thing is to match the tool to the joint rather than forcing the tool to do a job it was not designed for.
Mortar Rake Bit vs Diamond Cutting Disc: What Is the Difference?
A mortar rake bit is designed to work inside the joints between bricks or masonry blocks. Depending on its construction, it may use a diamond-coated working section or another abrasive cutting design to grind or remove the old mortar. The working width and profile determine how the bit enters the joint and how much material it removes.
A diamond cutting disc works differently. Its circular cutting edge is designed to make a narrow cut through the material for which the disc is rated. During repointing, a thin disc can be used to cut along the sides of a mortar joint, helping establish the boundaries of the material that needs to come out.
The difference becomes clear when working on an existing brick wall. A cutting disc that is too thick for the joint may rub against the brick edges, leaving chips or marks that remain visible after the repair. A mortar rake bit with the right working dimensions can make it easier to concentrate on the mortar itself, although poor control or an incorrectly sized bit can still damage the brickwork.
| Feature | Mortar Rake Bit | Diamond Cutting Disc |
|---|---|---|
| Main purpose | Removing mortar from masonry joints | Cutting specified construction materials |
| Working method | Grinds or cuts mortar according to its design | Cuts along a defined line |
| Narrow joints | Useful when the bit fits the joint | Thin discs may work; thicker discs can damage brick edges |
| Straight cutting lines | Depends on the bit design | One of the main advantages of a cutting disc |
| Main concern | Choosing the correct bit dimensions and operating method | Controlling cutting depth and keeping the disc within the joint |
Neither tool is automatically faster or more durable. A worn attachment, hard mortar, poor access, or an unsuitable tool size can slow the job down regardless of which option is used.
When Should You Use a Mortar Rake Bit?
A mortar rake bit is a logical choice when the main task is clearing deteriorated mortar from brick joints before applying fresh mortar. Rather than selecting a general-purpose cutting blade and adapting it to the job, you can choose a tool designed specifically for mortar removal.
This is particularly useful on walls with numerous joints to clean. Working along one joint after another requires consistent control, and the tool needs to reach the mortar without repeatedly catching the brick edges. A bit with the correct working width can make this process more manageable.
The shape and dimensions of the bit matter just as much as its diamond construction. A bit that is too wide may grind into the bricks, while one that is too small may require additional passes to remove the necessary amount of mortar. Check both the working width and the overall dimensions before buying, especially if the wall has narrow or uneven joints.
Mortar rake bits are not limited to one type of masonry, but performance varies with the tool design and the material being removed. Dense cement mortar, soft lime mortar, and heavily deteriorated joints present different challenges. On older brickwork, aggressive mechanical removal can do more harm than good, so a hand tool or specialist restoration method may be the better choice.
When Does a Diamond Cutting Disc Make More Sense?
A diamond cutting disc is useful when the job calls for a straight, controlled cut and the disc thickness matches the joint. It is a familiar tool for many masonry workers, and an appropriate disc can remove mortar efficiently when used within its intended application.
The main difficulty is keeping the cut within the mortar joint. On a long, straight wall with consistent joints, this may be relatively straightforward. On uneven brickwork, narrow joints, or walls with damaged brick edges, maintaining the same cutting line becomes more demanding.
Cutting depth also needs attention. Going too deep can remove sound material and create unnecessary work, while cutting too shallow may leave deteriorated mortar behind. Neither outcome helps the repointing process.
A diamond cutting disc is therefore a reasonable choice when its dimensions suit the joint and the operator can maintain a controlled cutting path. If the disc is wider than the joint, switching to a narrower accessory or a dedicated mortar rake bit is generally more sensible than trying to compensate by changing the angle of the grinder.
How Deep Should You Remove Mortar Before Repointing?
Removing the old mortar to the correct depth is just as important as choosing the tool. If loose or deteriorated mortar remains in the joint, the repair may not provide a sound base for the new material. Cutting much deeper than necessary, however, adds time and can damage the surrounding masonry.
For traditional brick repointing, a commonly cited guideline is to remove mortar to approximately two to two-and-a-half times the joint width. The National Park Service's guidance for historic masonry discusses this type of depth requirement, although the exact dimensions must be considered in the context of the masonry and repair specification.
For many ordinary brick joints, around 12–20 mm (1/2–3/4 inch) may be a useful initial reference, but it is not a universal requirement. The required depth can be greater or smaller depending on the joint width, the condition of the existing mortar, and the requirements of the replacement mortar.
The aim is to remove deteriorated material and provide enough depth for the specified repointing work, not simply to reach a particular number on a ruler. Stop and reassess if the brick edges begin to break away or if the existing masonry is softer than expected. Historic brickwork and lime-mortar joints often need a more careful approach than modern, hard-fired brickwork with cement-based joints.
How to Remove Mortar Without Damaging the Bricks
Most avoidable damage happens when the tool is too large for the joint, the operator cuts too deeply, or the grinder is difficult to control. Before starting, inspect the wall and identify loose bricks, cracked joints, and fragile areas that may need a different method.
Choose the attachment according to the joint dimensions and the required removal depth. Fit it according to the manufacturer's instructions, check that the connection is correct, and make sure the accessory's rated speed is compatible with the grinder. Never remove the guard to reach a narrow joint or exceed the accessory's maximum permitted speed.
Start in a small test area and work steadily along the joint. Let the tool remove the mortar without forcing it against the brick edges. If the bit or disc repeatedly catches the bricks, stop and check the dimensions, cutting angle, and tool selection rather than applying more pressure.
Dust is another practical issue. Grinding mortar can produce large amounts of airborne dust, including respirable crystalline silica from silica-containing masonry. Use effective dust extraction or other suitable exposure controls, along with the eye, hearing, and respiratory protection required for the task. Keep other people away from the work area and follow the grinder and accessory manufacturers' instructions.
Once the deteriorated mortar has been removed, clear loose debris from the joints and prepare them for repointing according to the project specification. A clean, properly prepared joint is more important than removing extra material simply to make the joint look wider.
Quick Guide: Which Tool Should You Choose?
Choose a mortar rake bit when you are primarily removing old mortar before repointing and can select a bit designed for the joint dimensions. It is often the more direct choice for dedicated mortar removal.
Choose a diamond cutting disc when you need straight cuts and have a disc whose thickness and application rating match the work. It can be effective on consistent joints when the cutting path and depth can be controlled.
Consider hand tools or specialist advice when working on historic buildings, soft bricks, lime mortar, or masonry that is already damaged. Mechanical removal is not always the safest way to preserve older brickwork.
Before purchasing either tool, check the working dimensions, connection type, and rated operating speed. A tool that fits the job properly is more useful than one selected simply because it is larger, more aggressive, or already available in the workshop.
Frequently Asked Questions
Is a mortar rake bit better than a diamond cutting disc?
For dedicated mortar removal during brick repointing, a mortar rake bit is often the more purpose-built option. A diamond cutting disc can be effective when its thickness and cutting geometry match the joint. The right choice comes down to the masonry, the joint dimensions, and the type of cut required.
Can I use an angle grinder to remove mortar between bricks?
Yes. An angle grinder fitted with a compatible mortar rake bit or a diamond cutting disc rated for the application can remove mortar between bricks. The attachment must match the grinder's mounting system and operating speed, and the operator must control the cutting depth to avoid damaging the brickwork.
How deep should mortar be removed before repointing?
A commonly cited guideline for traditional brick repointing is approximately two to two-and-a-half times the joint width. Around 12–20 mm (1/2–3/4 inch) can serve as a reference for some brick joints, but the required depth varies with the masonry, existing mortar, and project specification. Historic or fragile walls may require specialist advice.
Can a mortar rake bit damage bricks?
Yes. A bit that is too wide, aggressive operation, or poor control can damage the edges of the bricks. Select the working dimensions carefully, test the tool on a small area, and stop if the brickwork begins to chip or break away.
Should I use a mortar rake bit or a diamond disc for hard mortar?
Hard mortar may require a more careful choice of tool and operating method, but hardness alone does not determine which attachment is best. Consider the joint dimensions, the condition of the bricks, and the tool manufacturer's application guidance. On older masonry, do not assume that a more aggressive tool is the best solution.
Can every mortar rake bit fit an angle grinder?
No. Connection types, dimensions, and speed ratings vary between products. Check the manufacturer's specifications and confirm that the accessory is approved for your grinder before installation.
Choosing the Right Tool for Your Repointing Job
For most routine repointing projects, start by looking at the condition of the mortar and the dimensions of the joints. A dedicated mortar rake bit is often the more direct option for removing old mortar, while a diamond cutting disc is useful when the job calls for straight cuts and the disc fits the joint.
DIASHARK mortar rake bits are an option for users looking for a dedicated mortar removal tool. Check the product's working dimensions, connection, and operating requirements against your equipment and the job before ordering. The aim is straightforward: remove the mortar that needs replacing, preserve the surrounding brickwork, and leave the joints ready for the next stage of the repair.