You are halfway through cutting a thick piece of rebar, leaning hard into your 4-1/2″ angle grinder. Suddenly, the RPMs drop, the tool shudders, and a thick cloud of acrid, toxic smoke pours out of the cooling vents. The motor is completely fried.
For most guys, a smoking grinder goes straight into the trash, followed by a frustrating trip to the hardware store to drop $90 on a replacement bare tool. But if you rely on popular grinder models like the 9557NB or 9557PB series, throwing the tool away is a massive waste of money. The gears are fine. The housing is fine. You just destroyed the electrical heart of the machine.
By dropping in an aftermarket motor rebuild kit (compatible with part numbers 513633-7 and 625758-6), you can completely resurrect your grinder in under 20 minutes.
The Diagnostic: Why You Need the Complete Kit
When a grinder motor burns out under a heavy load, it rarely damages just one component. The motor consists of two main parts: the spinning armature (513633-7) and the stationary stator or field coil (625758-6).
If you push the grinder too hard, the heat melts the protective enamel on the copper windings. When the armature shorts out and melts, it almost always arcs against the stator, permanently damaging those windings as well.
Mechanic’s Rule: Never replace just a burnt armature and leave a heat-damaged stator in the tool. The compromised stator will pull excessive amperage and instantly burn up your brand-new armature the second you turn it on. Always replace them as a matched pair.
OEM vs. Premium Aftermarket: The Smart Choice
Sourcing Original Equipment Manufacturer (OEM) parts for a complete rebuild often costs almost as much as a brand-new grinder, defeating the purpose of the repair.
A premium aftermarket rebuild kit solves this math problem. These compatible kits are manufactured to the exact physical dimensions of the factory parts. They feature high-temperature copper windings designed to handle aggressive masonry and metal cutting, providing factory-level torque and RPMs at a fraction of the cost. This is the exact strategy independent repair shops use to keep job site tools running.
The Tear-Down: How to Install the 513633-7 & 625758-6 Kit
You don’t need a degree in electrical engineering to perform this heart transplant. Grab a Phillips screwdriver and a flathead.
- Strip the Housing: Unplug the grinder. Remove the rear tail cover and pull the carbon brushes out so they don’t snap when you remove the armature. Unscrew the gear housing from the main motor body.
- Extract the Armature: Pull the gear housing forward. The armature (513633-7) will come out attached to it. Unbolt the armature from the gear housing. Keep track of the rubber bearing boot!
- Pull the Stator: Disconnect the four wire leads connecting the stator to the switch and power cord. Remove the two long baffle screws holding the stator (625758-6) in place, and slide it out of the plastic housing.
- Drop in the New Kit: Slide the new aftermarket stator into the housing and reconnect the four wire leads. Bolt your new armature to the gear housing, ensure the rubber bearing boot is in place, and slide the assembly through the new stator.
- Button it Up: Fasten the gear housing to the motor body. Reinstall your carbon brushes, and screw the rear tail cover back on.
The Break-In Period (Don’t Skip This)
Do not immediately take your rebuilt grinder and bury it in a concrete block. The new copper commutator on your armature needs to “seat” with the carbon brushes. Run the grinder in the air with absolutely no load for 3 to 5 minutes. This grinds the flat brushes into a perfect curve against the spinning motor, preventing heavy sparking and maximizing the lifespan of your repair.
Stop trashing perfectly good tools. Grab the complete Aftermarket 513633-7 & 625758-6 Rebuild Kit right here and get your grinder back on the job today.
Frequently Asked Questions (Tech Q&A)
What causes an angle grinder motor to burn up?
The most common cause is severe overloading. When you press too hard during a cut, the motor RPMs drop, reducing the airflow from the internal cooling fan. The electrical current spikes, generating extreme heat that melts the insulation on the copper windings, leading to a dead short.
Can I reuse my old carbon brushes with the new motor kit?
It is highly discouraged. If your previous motor burnt out, the extreme heat likely damaged the old carbon brushes or altered their tension springs. Always install a fresh set of compatible carbon brushes when dropping in a new armature and stator to ensure clean electrical contact.
¿Este kit de inducido y estator es compatible con mi esmeriladora?
Sí. Este kit de repuesto (aftermarket) que reemplaza las piezas 513633-7 y 625758-6 está diseñado para encajar perfectamente en los modelos populares de 4-1/2″, como la serie 9557NB y 9557PB. Restaura la potencia y las RPM originales de fábrica.
Premium Aftermarket Motor Rebuild Kit (513633-7, 625758-6) Compatible with Makita Angle Grinders | FixPartHub
- ⚡ The Ultimate “Dead Grinder” Cure: Stop guessing which part failed. This comprehensive rebuild kit includes the Armature (513633-7), Stator/Field (625758-6), Carbon Brushes (194160-9/CB-325), and Bearing (211332-2) for a complete motor overhaul.
- 🔧 Broad Compatibility: Precision-engineered aftermarket parts strictly designed to be compatible with popular 4″ and 4-1/2″ angle grinders, including models 9553NB, 9554NB, and 9555NB.
- 🛡️ Heavy-Duty Copper Windings: Both the armature and stator feature high-grade, heat-resistant copper wiring coated with protective resin to withstand heavy grinding applications without burning out.
- ⚙️ Precision Rotation: The included 211332-2 aftermarket ball bearing ensures zero shaft wobble, reducing vibration and preventing premature wear on your newly installed carbon brushes.
- 💰 Save Your Tool & Wallet: Don’t throw away a perfectly good tool housing and gearbox. FixPartHub’s premium aftermarket kit restores factory-level RPM and torque at a fraction of the cost of a new bare tool.