Are Drills Supposed to Spark? (How to Repair)


You’re here because you’ve noticed that your drill sparks and it’s causing you concern. When I purchased my first drill years ago, I also found the sparking quite alarming. In this article, we’re going to take a look at whether this is part of normal operation or whether it’s a cause for concern.

An electric drill is supposed to spark if it has a brushed DC motor. These sparks should be consistent and relatively contained inside the drill. However, if there are intermittent and violent sparks around the motor, power cord, or battery compartment, this is sign of an issue that must be repaired.

If your drill has large, white sparks, you need to stop using it immediately as it is a danger to you and can cause irreparable damage to the drill. Fortunately, dangerous sparking is completely preventable with proper maintenance. Let’s have a look at how.

When sparking is normal

Most drills use a brushed direct-current motor to convert electrical energy to rotate the drill bit. The brushes produce sparks from the electromagnetic charge which are clearly visible inside your drill. Sparks around the motor that are consistent are completely normal and will occur when your drill is running at any speed.

Although sparking is part of normal operation, you should exercise caution as the sparks have the potential to ignite debris in the air such as sawdust. It’s even possible for them to ignite gas, so ensure that your work area is well-ventilated.

Sparking at the drill bit might also occur when it comes into contact with fragments of metal or composite materials. Although not dangerous, sparking at the drill bit causes damage to the bit, so you should stop drilling to prevent further damage.

When sparking is dangerous

Intermittent or spontaneous, violent sparking is a sign that there’s an issue with your drill. Larger sparks are white and cause a lot of damage to the motor’s performance.

Sparks at the power socket or at the point where the power cord enters the drill are dangerous, and you should stop using the drill immediately. The price to repair the power cord including labour will be around £38 ($46). Unless you have a particularly expensive drill, it’s probably best to invest in a new drill.

Sparking in a cordless drill should never occur around the battery compartment. It’s a sign that it’s probably shorting and can occur even when the battery isn’t attached to the drill. Cleaning the battery’s contacts might resolve the problem, but if it doesn’t, you must replace the battery for your safety.

Identifying the causes of sparking

The main cause of sparking is with the brushes and commutator in the motor armature. This is caused by inevitable wear on the brushes and the build-up of grime on the commutator.

Drill brushes are mostly made up of carbon. When the brushes and commutator move together, they create wear and the brushes release fine particles of dust which is conductive. The dust has nowhere to go and so accumulates within the commutator’s slots.

The result of such build-up is large, white sparks. In theory, the centrifugal force should keep the slots clean; however, humidity or a slow shaft speed (RPM) cause the dust to accumulate.

If the brushes wear out completely, the motor will begin to underperform and eventually fail. It’s essential to make a visual inspection of the motor armature from time-to-time to prevent this from happening.

How to repair and maintain the brushes and commutator

Open up the drill and inspect the brushes. Check the length of the brushes to ensure that they haven’t worn so far that they’re no longer making contact with the commutator. If they’re too short, you will need to order replacements.

Order replacement brushes from your local hardware store or from the manufacturer. A new pair of brushes will be around £15 ($18). Installation is as simple as removing the worn brushes and replacing with the new ones. If you replace the brushes, you must clean the commutator before using the drill again.

If the brush length is fine, then they will just need a cleanup. Remove the brushes and gently clean the curved end of each one with a fine-grit abrasive cloth (sandpaper).

Next, you will need to clean the commutator which is a bit more work. To do this you will need:

  • Protective eyewear
  • Disposable gloves
  • Electronic contact cleaner spray
  • Toothbrush
  • Sandpaper
  • Plastic scriber

In a well-ventilated area, generously spray the electronic contact cleaner all over the commutator, and scrub with the head of a toothbrush to remove the build-up of debris and oils.

Next, tear off or fold a strip of sandpaper to the same width as the commutator. Wrap it around the commutator and sand it in a full rotational motion (not just back and forth), making sure to do so in the path of travel and not against it.

Sanding can be done either by hand or by using a drill. If your drill has a large enough chuck, it is the preferred method as it will produce the most uniform results.

Lastly, clean out the slots of the commutator using a plastic scriber. This will clean out any debris from before and after sanding.

Ninja tip: When you open up your drill, take several photos of it from all angles or make a short video using your mobile phone before you start any repair work. This will avoid the dreaded problem of not knowing how to put it back together again.

Burning or smoking

Along with sparking, you may encounter a burning smell or even smoke coming from the drill. Again, this is often caused by worn brushes and an excess of grime on the commutator.

As we’ve already seen, the brushes wearing against the commutator produce dust which in turn produces sparking. If this problem is not addressed, and the build-up becomes heavy enough, it can cause a burning smell and even smoke.

If you experience burning or smoking from your drill, you need to stop using it immediately to avoid further damage. For most drills, at least some of the housing is made from plastic. Continuing to use a drill that is burning can melt the plastic housing, which will destroy your drill and is toxic when breathed in.

Buying a cheaper drill will also worsen the problem due to the sheer amount of plastic that makes up the housing.

A drill that produces a burning smell or smoke will definitely need its brushes replacing and a thorough cleanup of the commutator. Unfortunately, some motors on cheaper models are sealed and the commutator isn’t accessible. If this is the case, you will need to replace the entire motor.

Another reason for burning is because of extended, heavy use with a drill that isn’t up to the task. If your drill regularly gets too hot, consider buying a larger voltage drill. To know which drill voltage is best for your needs, check out my article on how to select a drill based on its voltage.

Related questions

Do brushless drills spark?

Brushless drills do not produce sparking as they are controlled by a computer instead of the mechanical, carbon brushes found in brushed drills.

Why do drills spark?

Sparking is due to the soft, carbon brushes rubbing against the hard, copper commutator. When two parts rub together, the materials need to be of a different hardness so that the soft part can wear to the shape of the hard part. Carbon is softer than copper which is why you need to replace the brushes every so often.

This also explains why they’re called brushes. Originally, they were copper wire brushes, but because both the brushes and commutator were made from copper (two hard parts) and rubbing together, both parts wore out quickly.

Graham Walsh

I want to share everything I know about home improvement in order to help you. Whether you're a home enthusiast or an industry professional, I have the information that you need.

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