Changing an angle grinder disc is a straightforward job once you understand how the spindle, flange and locking nut work. You may need to change a disc when switching from cutting to grinding, replacing a worn disc or fitting a different accessory for another type of job.
The exact method can vary between angle grinders, but most use one of three systems:
- A spindle lock button and two-pin wrench
- A spindle lock and tool-free quick-change nut
- A manufacturer-specific disc-changing system
Before changing any disc, the most important step is to isolate the grinder from its power source. Unplug a corded grinder or remove the battery from a cordless model before touching the disc or spindle.
In this beginner’s guide, we’ll show you how to change an angle grinder disc safely, explain how the different locking systems work and cover some common mistakes to avoid.
We’ll also look at how to choose the right replacement disc and what to check before switching the grinder back on.
If you’re unsure which type of disc you need, my guide to Cutting vs Grinding Discs: What’s the Difference? can help you understand the difference between the main types.
Quick Answer: How to Change an Angle Grinder Disc
Disconnect the grinder from power, lock the spindle, loosen the flange nut with the correct tool, remove the old disc, fit the new disc correctly and tighten the nut without overtightening. Check the disc, guard and fitting before reconnecting the grinder.
Step‑by‑Step Guide: How to Change an Angle Grinder Disc
1. Disconnect the Power
Before you touch the disc, make sure the angle grinder is completely isolated from its power source.
The correct method depends on whether you are using a corded or cordless grinder:
- Corded grinder: switch it off and unplug it from the mains socket.
- Cordless grinder: switch it off and remove the battery.
- Never rely on the trigger or power switch alone when changing a disc.
Place the grinder on a stable surface with the disc facing away from you before starting the disc-changing process.
Once the grinder is disconnected, wait for the disc to come to a complete stop if it has been running. Do not attempt to stop the disc by hand.
Check Before You Start
Before removing the old disc, take a moment to check the grinder and the disc:
- Make sure the grinder is disconnected from its power source.
- Check that the existing disc has completely stopped.
- Inspect the disc for cracks, chips or other visible damage.
- Make sure the spindle, flange and locking nut are free from excessive dirt or debris.
- Check the grinder manufacturer’s instructions if you’re unsure how its disc-fitting system works.
With the grinder safely isolated, you can now use the spindle lock button to hold the spindle while loosening the locking nut.
2. Press the Spindle Lock Button
Most angle grinders have a spindle lock button that holds the spindle in place while you loosen or tighten the disc-locking nut. The button is usually located on the top or side of the grinder head, although its position can vary between models.
How to Lock the Spindle
- Make sure the grinder is disconnected from its power source.
- Press and hold the spindle lock button.
- Slowly rotate the disc or spindle by hand until you feel the lock engage.
- Keep the button pressed while checking that the spindle is locked securely.
You may need to rotate the disc slightly before the locking mechanism engages. Do not force the spindle lock button if it does not engage easily.
Once the spindle is locked, the disc-locking nut can be loosened using the appropriate wrench or tool supplied with your grinder.
Important: Do not press the spindle lock while the grinder is running or while the spindle is rotating under power. The spindle must be completely stopped and the grinder disconnected before using the lock.
The exact spindle-lock mechanism can vary between manufacturers, so if you’re unsure how yours works, check the grinder’s instructions before continuing.
3. Loosen the Disc Using the Two‑Pin Wrench
Once the spindle is locked, you can loosen the locking flange nut using the two-pin wrench supplied with many angle grinders. The wrench has two small pins that fit into the holes in the flange nut.
How to Loosen the Nut
- Insert the two pins of the wrench into the corresponding holes in the locking nut.
- Hold the grinder securely while keeping the spindle locked.
- Turn the wrench in the direction specified by your grinder’s instructions to loosen the nut. On many common grinders, this will be anti-clockwise when viewed from the disc side.
- Once the nut is loose, remove it by hand.
- Remove the old disc from the spindle.
Watch Out for the Wrench Slipping
One thing worth knowing from my own practical experience is that the two-pin wrench can slip out of the holes when you apply force. If this happens unexpectedly, your hand can move quickly and you can catch your knuckles against the grinder or another part of the tool.
To reduce the chance of this happening:
- Make sure both pins are properly seated in the holes before applying pressure.
- Keep a firm grip on the grinder and wrench.
- Apply controlled pressure rather than suddenly forcing the wrench.
- Keep your fingers and knuckles clear of nearby edges.
- If the wrench keeps slipping, stop and check that you’re using the correct wrench and that the spindle lock and flange are correctly positioned.
Don’t force the wrench if the nut will not move. Check that the spindle lock is properly engaged and that you’re using the correct wrench for your grinder. Some grinders use different locking systems or flange arrangements, so always follow the manufacturer’s instructions if they differ from the procedure above.
For additional guidance on the safe use of abrasive wheels, see the relevant HSE guidance on abrasive wheels.
Check the Old Disc
With the disc removed, take a moment to inspect it. If it is cracked, chipped, excessively worn or otherwise damaged, dispose of it appropriately rather than attempting to reuse it.
Keep the flange and spindle area reasonably clean so the replacement disc can sit correctly against the backing flange.nd spindle area reasonably clean so the replacement disc can sit correctly against the backing flange.
4. Fit the New Disc
With the old disc removed, you can now fit the replacement. Take your time at this stage because the disc needs to sit correctly and be suitable for your particular grinder.
How to Fit the Disc
- Check the replacement disc for cracks, chips or other visible damage before fitting it.
- Check that the disc diameter and bore size are compatible with your grinder.
- Make sure the backing flange and spindle are clean and free from debris.
- Place the disc onto the spindle and make sure it sits flat against the backing flange.
- Check any directional arrows, labels or mounting markings on the disc and follow the manufacturer’s instructions.
- If the disc has a specified mounting direction, fit it accordingly. Do not assume that the printed label should always face outward.
- Make sure the disc is centred correctly and is not sitting at an angle.
For some abrasive discs, the mounting arrangement can vary depending on the disc design and the grinder. Diamond blades and other accessories may also have specific directional markings, so always follow the instructions supplied with the disc.
Which Disc Should You Fit?
| Grinder | Common disc size |
|---|---|
| Small angle grinder | 115mm |
| Small/medium angle grinder | 125mm |
| Large angle grinder | 230mm |
But I stress that you must check the grinder’s specification rather than choosing by appearance.
Check the Disc Before Tightening
Before fitting the locking nut, look around the disc and flange to make sure there is nothing trapped underneath it.
The disc should sit securely and evenly against the backing flange. If it does not sit correctly, remove it and check the setup rather than trying to tighten it into position.
Once the disc is correctly positioned, you can refit the locking flange nut and tighten it using the appropriate method for your grinder.
5. Tighten the Flange Nut
Once the new disc is correctly positioned, refit the locking flange nut to secure it in place.
How to Tighten the Nut
- Place the locking flange nut onto the spindle, making sure it is seated correctly.
- Thread the nut on by hand first to make sure it is not cross-threaded.
- Press and hold the spindle lock button to lock the spindle.
- Use the appropriate wrench supplied with your grinder to tighten the nut.
- Tighten it firmly, but do not overtighten it.
The aim is to hold the disc securely against the backing flange without using excessive force. Over-tightening can make the nut unnecessarily difficult to remove the next time you change the disc.
If your grinder uses a tool-free quick-change nut, follow the manufacturer’s instructions instead of using the two-pin wrench.
Check the Disc Is Secure
Before reconnecting the grinder to its power source:
- Make sure the disc is sitting flat and centrally.
- Check that the locking nut is secure.
- Make sure the disc can rotate freely without catching the guard.
- Check that the correct guard is fitted and positioned for the accessory being used.
If anything looks unusual or the disc does not appear to be sitting correctly, do not switch the grinder on. Remove the disc and check the fitting again.
Once everything is secure, the grinder can be reconnected to its power source and the disc checked before use.
6. Check the Disc Before Use
Before switching the grinder back on, carry out a final check to make sure the disc is fitted correctly and the grinder is ready to use.
Final Checks
- Make sure the disc is suitable for the material and job you are about to do.
- Check that the disc is the correct diameter and bore size for the grinder.
- Make sure the disc is seated correctly against the backing flange.
- Check that the locking nut is secure without being excessively tightened.
- Inspect the disc for cracks, chips or other visible damage.
- Make sure the correct guard is fitted and positioned for the accessory being used.
- Check that the disc is not touching the guard or another part of the grinder.
- Make sure the workpiece is secure and your working area is clear.
Once these checks are complete, reconnect the grinder to its power source.
Let the Grinder Reach Full Speed
Hold the grinder securely and position it so that you are not in line with the plane of the disc. Start the grinder and allow the disc to reach its normal operating speed before bringing it into contact with the workpiece.
Pay attention to the grinder during this initial run. If you notice unusual vibration, wobbling, excessive noise or anything else that does not seem normal, switch it off and disconnect the power before investigating.
Do not use a disc that appears damaged or does not run correctly.
Never try to stop a rotating disc with your hand. Allow it to come to a complete stop before putting the grinder down.
Alternative Methods
1. Tool-Free Quick-Change Nuts
Some angle grinders use a tool-free quick-change nut that allows you to remove and fit discs without the two-pin wrench.
The exact operation varies between manufacturers, but the process generally involves:
- Disconnecting the grinder from its power source.
- Locking the spindle using the grinder’s spindle-lock mechanism.
- Releasing the quick-change nut according to the manufacturer’s instructions.
- Removing the old disc.
- Fitting the replacement disc correctly.
- Securing the quick-change nut as specified by the manufacturer.
These systems can make disc changes more convenient, particularly if you regularly switch between different accessories.
Do not assume that every quick-change nut works in the same way. Check the instructions for your particular grinder before attempting to remove or tighten one.
2. Manufacturer-Specific Disc Systems
Some grinders and accessories use their own disc-fitting or locking arrangements. These may differ from the traditional spindle-lock and two-pin wrench system.
If your grinder does not match the procedure in this guide:
- Check the manufacturer’s instructions.
- Use the correct fitting components supplied with the grinder.
- Make sure the replacement disc is compatible with the grinder.
- Follow any specific instructions about the disc’s mounting direction or locking system.
Never force a disc, flange or locking nut into position simply because it looks like it should fit.
If you’re unsure how your particular grinder’s disc-changing system works, check the manufacturer’s instructions before proceeding.
Common Mistakes to Avoid
Changing an angle grinder disc is relatively simple, but a few common mistakes can cause problems or make the disc difficult to remove later.
Forgetting to Disconnect the Grinder
Never start changing a disc while the grinder is still connected to its power source.
- Unplug corded grinders.
- Remove the battery from cordless grinders.
- Do not rely on the power switch alone.
Using the Wrong Disc
Make sure the replacement disc is suitable for both the grinder and the job.
Check the:
- Disc diameter
- Bore size and fitting
- Maximum operating speed
- Material or application rating
- Manufacturer’s instructions
A disc that physically fits the spindle is not necessarily suitable for the grinder or the work you intend to do.
Overtightening the Flange Nut
The locking nut needs to secure the disc, but it should not be tightened excessively.
Over-tightening can make the nut difficult to remove when you next change the disc and can make disc changes unnecessarily difficult.
Not Seating the Disc Correctly
The disc should sit flat and centrally against the backing flange.
If it appears crooked, moves around or does not sit correctly, remove it and check the flange, spindle and disc rather than trying to tighten it into position.
Assuming the Disc Label Always Faces Outward
Don’t automatically fit every disc with the printed label facing outward.
Some discs and accessories have specific mounting directions or markings. Follow the instructions supplied with the disc and grinder, including any directional arrows.
Using the Wrong Wrench
Use the correct wrench or disc-changing tool supplied or specified for your grinder.
If the two-pin wrench keeps slipping from the flange nut, stop and check that the pins are correctly positioned and that you are using the correct tool. Avoid applying excessive force if the nut will not move.
Forgetting the Guard
Check that the correct guard is fitted and positioned for the accessory you are using before operating the grinder.
The guard should not interfere with the disc’s free movement.
Failing to Check the Disc Before Starting
Always inspect the replacement disc before use. Do not fit a disc that is cracked, chipped, damaged or otherwise unsuitable.
After fitting the disc, carry out a final check before reconnecting the grinder and allow the disc to reach normal operating speed before using it on the workpiece.
If you notice unusual vibration, wobbling or anything else that does not seem normal, switch the grinder off and disconnect it before investigating.
Which Disc Should You Fit?
he correct replacement disc depends on what you are trying to do and what material you are working on. Don’t choose a disc simply because it fits your grinder.
Here’s a quick guide:
| Job | Suitable accessory |
|---|---|
| Cutting steel, bolts or threaded rod | Suitable metal cutting disc |
| Grinding welds or removing excess metal | Grinding disc |
| Smoothing and blending metal | Flap disc |
| Fine finishing metal | Finer-grit flap disc |
| Removing surface rust or loose paint | Wire wheel or cup brush |
| Cutting brick, block or suitable masonry | Diamond cutting disc rated for masonry |
Always check the disc manufacturer’s instructions before fitting an accessory, particularly when working with materials such as stainless steel, aluminium, masonry or other specialist materials.
Also check the disc’s:
- Diameter
- Bore or fitting
- Maximum operating speed
- Material/application rating
- Mounting instructions
Don’t Use One Disc for Every Job
A common beginner mistake is assuming that one type of disc can be used for everything. Cutting discs, grinding discs, flap discs, wire wheels and diamond discs are designed for different applications.
For example, a cutting disc should not be used for side grinding, while a grinding disc should not be used to cut through material.
If you’re unsure which accessory you need, see my guide to Angle Grinder Discs Explained, which covers the main disc and accessory types in more detail.
Once the new disc is fitted, always check the disc, guard and grinder before use. It may help to read my guide on changing an angle grinder disc safely. If you’re unsure whether a disc is suitable, check the manufacturer’s instructions rather than taking a chance.