Carbon Brush Resources
Explore Resources for Your Carbon Brushes
At Helwig Carbon, we are committed to providing industry-leading expertise, technical guidance, and educational materials to help you get the best performance from your carbon brushes and related components. Whether you’re looking for installation support, troubleshooting tips, or in-depth technical data, this resource hub brings together everything you need in one place.
Additional Education, Installation, and Troubleshooting FAQ
Proper installation and maintenance are critical to maximizing the service life of carbon brushes. Our detailed FAQs provide step-by-step guidance and solutions for common issues, including:
- How to correctly install and seat new brushes
- How to identify and diagnose operational problems
- Best practices for extending brush life
- Tips for maintaining brush holders and slip rings
These expanded FAQs offer practical, technician-focused recommendations designed to improve uptime and reduce maintenance costs.
Carbon Brush 101
What is a carbon motor brush?
A carbon brush is an electrical contact that is used in a motor or generator to conduct electricity between the stationary (armature or stator) and rotating (rotor) parts of electrical machines. This transfer of current is essential for the motor or generator to operate.
The basic form of a carbon brush is a block of carbon graphite material, which rides on the contact surface, with a wire leading to a terminal or cap making a stationary electrical connection.
What are brushes made of? (Grade)
Helwig’s electrical brushes are made from low friction, conductive carbon materials that include natural graphite, carbon graphite, silver graphite, copper graphite, and electro graphite.
Graphite:
Graphites are for use in special applications requiring the low-friction characteristics of this material. When brushes must operate at very low current densities or very high peripheral speeds, a graphite grade should be used.
Carbon Graphite:
Carbon Graphites offer cleaning action for use at slow speeds, low current densities and medium to low voltages. These grades were developed early in the history of motors and generators and are found most often on older equipment, particularly with flush mica commutators.
Electrographite:
Electrographites are the most common grades used on modern equipment with good performance at high voltages, high current densities, and high speeds. There is a wide range of characteristics within this category. Most electrographite grades are capable of handling overloads well.
Silver Graphite:
Silver graphites have material contents of 15–95% silver. The added conductivity and lower voltage drop of the metals allow metal graphite brushes to perform well at very high current densities and low voltages.
Copper Graphite:
Copper graphites have material contents of 15-95% copper or copper alloy. The added conductivity and lower voltage drop of the metals allows metal graphite brushes to perform well at very high current densities and low voltages.
For more information about materials and brush grades, please visit our Grade Information page.
What do the numbers on my brushes mean? (Marking)
The numbers on your brushes display vital information about the brush.
Commonly these numbers include:
- Grade Information
- Helwig Carbon Part Number
- OEM Part Number
- Customer Part Number
More information in our video “How to Properly ID a Carbon Brush”
How do I identify my brush grade?
Brush grades are typically found stamped or marked on the front side of the brush. The grade designates the material composition of the brush.
Brush grades are regularly organized according to the manufacturing processes and the types of materials used. Grades are determined through a variety of raw materials, molding pressures, temperatures, duration of the baking process, and post-process treatments. Material elements provide different levels of resistivity, hardness, and strength that directly affect friction, contact-drop, and surface film.
How do I measure a brush?
Brush sizes are designated as: Thickness x Width x Length of the carbon. If the brush design includes a Red Top, the length measurement should include the pad. On brushes with bevels, the length is measured on the long side. Brushes with a head on top include the length of the head. When specifying dimensions as a reference, submit information on brush length even if it is the worn length.
More information in our video “How to Properly ID a Carbon Brush”
What brush style configurations do you offer?
The primary brush styles we offer are:
- Wireless
- Tamped with Spring
- Tamped Single Wire
- Tamped Multiple Wires
- Tamped Multi-Section
- Tamped Paired Brushes
- Riveted Paired Brushes
- Riveted Single Wire Position
- Riveted Multiple Wire Position
- Riveted MultiSection
View the Helwig Brush Wall Chart to see over 200 styles.
If the required style is not listed, please contact [email protected] and submit photos, a drawing, and/or samples.
Installation, Seating & Troubleshooting
How do I install brushes in DC Motors?
The proper way to install a brush in a DC electric motor is:
1. Be aware of important safety and product guidance:
- Follow all plant and electrical safety procedures and use proper PPE when working with electrical rotating equipment.
- Don’t Mix and Match Brushes! Do not mix brushes from different manufacturers or different grades. This can lead to selective action.
2. Disconnect the power to the machine using approved lockout procedures.
3. Remove all old brushes from the holders and examine them. Make note of any unusual conditions of the brushes including roughness or burning of the contact face, polished sides on the carbon, excess heat on the wires, or frayed shunt wires. These are indications of the need for maintenance on the machine.
4. Replace all brushes per set at a time. This is always a good practice when feasible and will help in maintenance cycles for future monitoring and records.
5. Check the rotating surface for unusual conditions. Make note for required maintenance.
6. Check the inside holder cavity for dust, dirt, oil, deposits, corrosion, or burned areas and clean as needed.
7. Check the terminal connection area and clean as needed.
8. Measure spring forces to ensure there is consistent contact force at the recommended level.
9. If the new brushes are made from a different grade, then the old film must be removed from the brush tracks. A rubrite flexible abrasive is usually adequate for this task.
10. When brushes are installed in the holders, ensure that the constant force springs are locked in place to apply force on the top of the brushes.
11. Ensure that the brushes are moving freely in the holders.
12. Secure all terminal connections.
13. Seat the brushes to the contour of the rotating surface using non-metal bearing sandpaper or garnet paper. Do NOT use emery cloth. Medium coarse grade paper pulled under the brush face in the direction of rotation improves the quality of the brush contact and speeds the process. There should be at least 80% of the brush face seated to the contour of the contact surface prior to operating the machine. Once this level has been achieved, the resulting dust in the machine around the brushes, holders, and rotating surface should be vacuumed out.
14. In order to ensure complete electrical contact of the brushes, it helps to operate the machine at no load for the final wear-in contour of the contact surfaces, if possible.
15. If the machine has a history of issues, note the issues and check if they align with specific brush positions. Mark those brushes for easier tracking and data collection.
16. If springs are to be replaced, replace all springs at the same time to avoid selective action as old springs could be weak compared to new springs.
17. Initially monitor operation closely. Monitor more frequently when any change is made or on any new application. Once the brushes have been running for some time and the technician is satisfied with the performance, the PM cycle can be prolonged. This is on a case-by-case/application-specific basis. Carbon brushes or sliding electrical contacts are used in many different types of applications and operating conditions. The proper PM cycle will be left up to the end user—we just recommend making more initial checks for proper performance.
18. Most importantly, inform your supervisor when in doubt.
More information in our video “How to Install a Carbon Brush”
Why is there sparking between the commutator or rings and the brushes?
The brush is often blamed, but it is rarely the root cause of machine problems. Sparking at the brush face is typically indicative of an issue elsewhere in the system.
Common Reasons for Sparking:
- Brush holders are:
- Not evenly spaced
- Off electrical neutral
- Damaged or dirty
- Too far from the commutator surface
- Wrong interpole strength
- Overloads
- Defective armature windings
- Incorrect spring pressure
- Poor undercutting of commutator
- Foreign material on commutator surface
- Black commutator film
- Brushes binding in holder
- Restricted brush motion
- Out-of-round commutator
- High bars or flat spots
- Machine vibration
For more details and solutions on brush sparking download Brushes, Sparking and Machine Maintenance .
How do I seat brushes in a motor?
Below is a step-by-step guide to seat carbon brushes.
Initial Seating with Garnet Paper
Place the brushes in their holders with springs engaged to apply pressure. Insert a strip of abrasive linen—preferably garnet paper with 80-100 grit—between the brush and the rotating surface. Move the paper tangentially under the brush. Once the brush begins to conform to the surface, draw the paper in the direction of machine rotation to finish shaping. Lift the brushes before removing the paper.
Wrapping
Wrap a strip of garnet paper around the rotating surface and secure it with adhesive tape. Insert the brushes into their holders and again make sure the springs are engaged and applying pressure. Rotate the machine’s rotor in its operating direction. If the motor runs in both directions, choose one. Once the process is complete, remove the paper. If this step can’t be performed, ensure step 1 is done thoroughly, as more seating time may be required.
Final Seating
With all brushes installed and any remaining garnet paper removed run the machine at idle or reduced speed. Gently press a pumice or cleaning stone in front of the brushes. The resulting dust will help polish and contour the brushes further. This method is useful for large DC machines and may not be necessary for all motors.
When 75–80% of the brush face is contoured, the process is complete. Remove the brushes and vacuum out any dust. Avoid letting dust reach coils or bearings. Reinsert each brush into its original holder.
To view Helwig’s garnet paper listing click here. 4% discount on orders of 10 or more rolls!
Why are my brushes wearing so quickly?
For specifics to your application, please contact Helwig Engineering to diagnose your brush wear problem. Call (800) 962-4851 or Contact Us.
Rapid brush wear is a problem that can be caused by a multitude of factors. There isn’t one easy answer, as each situation can be different. A common assumption is that the carbon brush grade is the issue; however, in many cases, the brush grade is not the root cause.
The NUMBER ONE reason for increased brush wear is low spring pressure!
Inadequate spring pressure can lead to rapid electrical brush wear. Clock and finger-style springs tend to lose force as the brush wears, and all springs will fatigue over time. This reduces effective force at the brush face and increases wear rate.
Learn more on spring pressure in our blog: Increase Efficiency & Reduce Maintenance with Proper Spring Force.
To learn more about common causes of rapid brush wear for generator, slip ring, and motor brushes, read our blog: 3 Reasons for Rapid Brush Wear.
When should I replace my brushes?
What happens when brushes wear out?
When motor brushes wear out, the electric motor will arc & spark, and the electrical circuit may be incomplete. This situation can be dangerous and should be dealt with immediately. Usually, the problem can be solved by replacing the brushes.
For more details and solutions on brush sparking download Brushes, Sparking and Machine Maintenance.
Commutator Conditions - Identifying Problems and Causes
Why is Correct Spring Force So Important for Carbon Brush Function?
Spring force can have a dramatic effect on the life and performance of carbon brushes because it strongly influences both mechanical and electrical wear. Many brush performance issues are resolved by the spring rather than the carbon grade. Ignoring spring force can be inefficient at best and catastrophic at worst.
Measuring spring force allows you to detect issues before any damage is done to the brushes or motor.
Issues with Spring Force Can Cause:
- Rapid brush wear
- Threading of brushes and, in extreme conditions, damage to the contact surface
- Fraying of wires resulting in loss of current-carrying capacity. If not addressed,
wires can break, causing unintended current paths and potential failure - High-intensity arcing that may create grooves in the brush track
- Increased dusting with conductive metallic particles, which can lead to flashover
- Other commutator issues including streaking, bar edge burning, and copper drag
How Do I Measure Spring Force?
Labeled Brush Diagram
Bevel
Brush face
The surface of the brush which touches the commutator or slip ring. The condition of the brush face can be a good indicator of brush performance.
Cap
Concave
Also referred to as a concave radius.
Grade
The final composition of the raw material. Manufacturers give each unique composition a designation called a brush “grade” See Helwig Grades
Descriptions of the types of brush grades:
Graphite:
- Graphites are for use in special applications requiring the low friction characteristics of this material. When brushes must operate at very low current densities or very high peripheral speeds, a graphite grade should be used.
Carbon Graphite:
- Carbon Graphites offer cleaning action for use at slow speeds, low current densities and medium to low voltages. These grades were developed early in the history of motors and generators and are therefore found most often on older equipment, particularly with flush mica commutators.
Electro Graphite:
- Electrographites are the most common grades used on modern equipment with good performance at high voltages, high current densities and high speeds. There is a wide range of characteristics within this category. Most electrographite grades are capable of handling overloads well.
Silver Graphite:
- Silver graphites have material contents of 15–95% silver. The added conductivity and lower voltage drop of the metals allow metal graphite brushes to perform well at very high current densities and low voltages.
Copper Graphite:
- Copper graphites have material contents of 15-95% copper or copper alloy. The added conductivity and lower voltage drop of the metals allow metal graphite brushes to perform well at very high current densities and low voltages.
For more information about materials and brush grades, please visit our Grade Information page.
Head
Helwig Quick Disconnect (HQD) Terminal
Marking
A series of letters and numbers that delineate a specific brush from another.
Multi-Flex or Tri-Flex
Red Top Pad
Rivet connection
Shunt(s)
Shunt location
Sleeving
Slot
Spring Coil
Tamped Connection
Terminal
