Removing deteriorated mortar is often the most demanding part of any brick repointing or masonry restoration project. The process requires precision: remove too little mortar, and the new joint will not bond properly; remove too aggressively, and you risk damaging the surrounding brickwork.

Anyone who has used a traditional grinding blade for mortar removal knows the problem. A small movement mistake can easily chip the edge of a historic brick, turning a simple repair into an expensive restoration issue.

This is why professional masons increasingly rely on diamond mortar raking bits, also known as mortar removal bits, mortar grinding rods, or diamond mortar removal tools.

Unlike standard diamond cutting blades that create straight cuts, a mortar raking bit works like a compact rotary milling tool. Its cylindrical diamond surface allows controlled removal inside mortar joints, making it ideal for both horizontal bed joints and vertical head joints.

Whether you are restoring an old brick facade, preparing a wall for repointing, or removing failed mortar from commercial masonry, choosing and using the correct mortar raking bit can dramatically improve efficiency while protecting the surrounding bricks.

What Is a Mortar Raking Bit?

A mortar raking bit is a diamond-coated masonry tool designed specifically for removing old or damaged mortar from brick joints.

Unlike conventional grinding wheels, which remove material through a flat cutting surface, mortar raking bits are designed to enter the joint channel and remove mortar from the inside out.

They are commonly used for:

• Brick repointing projects
• Historic masonry restoration
• Removing cracked or weathered mortar
• Preparing joints before new mortar application
• Repairing damaged brick walls
• Cleaning masonry joints before tuck pointing

A quality diamond mortar removal bit provides controlled material removal, consistent joint depth, and reduced risk of damaging valuable brick surfaces.

Choosing the Right Mortar Raking Bit for Your Project

 

Not every mortar joint or masonry material requires the same diamond tool. Selecting the wrong size or diamond bond can reduce cutting performance and shorten tool life.

1. Match the Bit Diameter to the Mortar Joint Width

The diameter of your mortar grinding rod should typically be around 1–2mm narrower than the mortar joint width.

This allows the diamond surface to remove mortar effectively without grinding into the brick edges.

Recommended sizes:

6mm–8mm Mortar Raking Bits

Ideal for:

• Narrow vertical head joints
• Thin brick applications
• Decorative masonry work
• Detailed restoration projects

10mm–12mm Mortar Raking Bits

The most versatile option for:

• Residential brick repointing
• Standard mortar joints
• General masonry repair

15mm+ Mortar Raking Bits

Designed for:

• Wide historic mortar joints
• Large-format stone masonry
• Heavy restoration work

Choosing the correct diameter improves control and prevents unnecessary brick damage.

Understanding Diamond Bond Types: Vacuum Brazed vs Sintered

The diamond bonding process directly affects cutting speed, durability, and application range.

Vacuum Brazed Diamond Mortar Raking Bits

Vacuum brazed diamond tools have diamond particles directly bonded onto the steel body through a high-temperature brazing process.

Advantages:

• Extremely aggressive cutting performance
• Fast material removal
• Excellent for soft to medium mortar
• Lower initial tool cost

They are often preferred for renovation projects where speed and clean removal are important.

Sintered Diamond Mortar Raking Bits

Sintered diamond tools embed diamond particles throughout the metal matrix.

Advantages:

• Longer working life
• Better wear resistance
• Suitable for harder mortar materials
• More consistent performance over extended use

For dense Portland cement mortar or demanding commercial restoration projects, a sintered diamond design can provide better durability.

Essential Tools and Safety Equipment

Before starting mortar removal, prepare the correct equipment:

• Variable-speed angle grinder
• Diamond mortar raking bit
• Dust extraction shroud
• M-class vacuum extractor
• Safety glasses
• Respirator (N95/P3 recommended)
• Hearing protection
• Heavy-duty gloves

Mortar removal creates fine silica-containing dust. Proper dust extraction is not only recommended for cleaner work—it is essential for protecting respiratory health.

Always check the maximum RPM rating of the diamond bit before operation. Running a tool above its rated speed can cause excessive vibration, overheating, and premature failure.

Step-by-Step Guide: How to Use a Mortar Raking Bit

Step 1: Determine the Required Removal Depth

Before cutting, inspect the existing mortar condition and determine how much material needs to be removed.

For most repointing applications, professionals remove mortar to a depth of approximately:

15–25mm

A common guideline is to remove mortar at least twice the width of the joint to provide sufficient bonding space for new mortar.

For example:

A 10mm mortar joint generally requires around 20mm removal depth.

Step 2: Install the Mortar Raking Bit Correctly

Always disconnect power before installing the tool.

Installation steps:

1. Remove the existing grinder accessory.
2. Install the mortar raking bit onto the grinder spindle.
3. Secure the bit according to the manufacturer's instructions.
4. Confirm the tool rotates freely.
5. Check RPM compatibility.

Avoid loose installation. Excessive vibration can damage both the tool and grinder.

Step 3: Start With Vertical Head Joints

Professional masons usually begin with vertical joints before moving to horizontal bed joints.

Hold the grinder firmly with both hands.

Insert the diamond tip into the mortar joint and allow the diamonds to remove material gradually.

Use:

• Smooth upward and downward movement
• Controlled forward motion
• Light, consistent pressure

Do not force the bit into the joint. Diamond tools cut through controlled abrasion, not excessive pressure.

Step 4: Remove Mortar From Horizontal Bed Joints

After clearing vertical joints, move onto the longer horizontal joints.

Keep the grinder aligned with the brick course.

Maintain:

• Stable movement speed
• Consistent cutting depth
• Straight tool positioning

Avoid twisting the tool sideways. Side loading creates unnecessary stress on the bit connection and can shorten tool life.

Step 5: Clean the Joint Before Repointing

Removing mortar is only the first stage.

Before applying new mortar:

1. Brush out remaining debris.
2. Vacuum loose dust.
3. Clean the joint surface.
4. Ensure the cavity is free from contamination.

Dust-covered joints reduce mortar adhesion and may shorten the lifespan of the repair.

Dry vs Wet Mortar Raking: Which Method Works Better?

Dry Mortar Raking

Dry cutting is the most common method for brick restoration.

Advantages:

• Faster setup
• Easier operation
• No slurry cleanup
• Suitable for indoor and outdoor repairs

For best results, always use a dust extraction system.

Wet Mortar Raking

Wet cutting is less common for brickwork because water can create staining and cleanup problems.

However, it may be useful for:

• Dense stone masonry
• Heat-sensitive applications
• Heavy-duty restoration work

Always follow the tool manufacturer's recommended operating method.

5 Common Mistakes That Damage Mortar Raking Bits

1. Applying Excessive Pressure

More force does not mean faster cutting.

Excessive pressure causes:

• Faster diamond wear
• Increased heat
• Reduced cutting efficiency

Let the diamond segments perform the cutting.

2. Using the Wrong Bit Size

A bit that is too wide can damage brick edges.

A bit that is too narrow increases working time and unnecessary passes.

Choose the diameter based on the mortar joint width.

3. Side Loading or Levering the Tool

Mortar raking bits are designed for rotational cutting.

Do not:

• Twist inside the joint
• Pry out mortar pieces
• Apply sideways force

These actions can damage the steel core or connection thread.

4. Cutting Hidden Metal

Old masonry walls may contain:

• Steel wall ties
• Wire reinforcement
• Metal anchors

If you feel sudden resistance or see bright sparks, stop immediately and inspect the area.

Diamond tools are designed for masonry—not cutting steel.

5. Ignoring Tool Glazing

When a diamond bit slows down, the diamonds may be covered by worn metal matrix or mortar dust.

This condition is called glazing.

To refresh the cutting surface:

• Make several passes through abrasive concrete
• Use a diamond dressing stone
• Remove surface buildup

Fresh diamond particles will become exposed again.

How to Extend the Life of Your Diamond Mortar Removal Bit

Proper operation significantly improves tool lifespan.

Follow these practices:

• Keep the grinder moving during operation
• Avoid overheating
• Use the correct RPM
• Do not force the tool
• Clean threads after use
• Store tools in a dry environment

A professional-grade diamond mortar raking bit can complete multiple restoration projects when operated correctly.

Frequently Asked Questions About Mortar Raking Bits

Can a mortar raking bit damage bricks?

Yes, if the wrong size bit is used or excessive pressure is applied. Selecting a bit slightly narrower than the mortar joint helps protect brick edges.

What grinder can I use with a mortar raking bit?

Most mortar raking bits are designed for angle grinders with compatible spindle sizes, including M14 and 5/8"-11 systems. Always verify RPM compatibility.

How deep should mortar be removed before repointing?

Most professional repointing applications require removing approximately 15–25mm of old mortar, depending on joint size and repair requirements.

How long does a diamond mortar removal bit last?

Tool life depends on mortar hardness, operating technique, pressure, and cooling. Hard cement mortar typically wears tools faster than soft lime mortar.